diff --git a/build.json b/build.json
index 5b0d603..fe24e69 100644
--- a/build.json
+++ b/build.json
@@ -70,6 +70,7 @@
             "crypto/fipsmodule/hmac/hmac.cc.inc",
             "crypto/fipsmodule/keccak/keccak.cc.inc",
             "crypto/fipsmodule/mldsa/mldsa.cc.inc",
+            "crypto/fipsmodule/mlkem/mlkem.cc.inc",
             "crypto/fipsmodule/modes/cbc.cc.inc",
             "crypto/fipsmodule/modes/cfb.cc.inc",
             "crypto/fipsmodule/modes/ctr.cc.inc",
@@ -524,7 +525,6 @@
             "crypto/kyber/internal.h",
             "crypto/lhash/internal.h",
             "crypto/md5/internal.h",
-            "crypto/mlkem/internal.h",
             "crypto/obj/obj_dat.h",
             "crypto/pkcs7/internal.h",
             "crypto/pkcs8/internal.h",
diff --git a/crypto/fipsmodule/bcm.cc b/crypto/fipsmodule/bcm.cc
index 66e1365..6248b0a 100644
--- a/crypto/fipsmodule/bcm.cc
+++ b/crypto/fipsmodule/bcm.cc
@@ -88,6 +88,7 @@
 #include "hmac/hmac.cc.inc"
 #include "keccak/keccak.cc.inc"
 #include "mldsa/mldsa.cc.inc"
+#include "mlkem/mlkem.cc.inc"
 #include "modes/cbc.cc.inc"
 #include "modes/cfb.cc.inc"
 #include "modes/ctr.cc.inc"
diff --git a/crypto/fipsmodule/bcm_interface.h b/crypto/fipsmodule/bcm_interface.h
index 0c702f3..25b0a32 100644
--- a/crypto/fipsmodule/bcm_interface.h
+++ b/crypto/fipsmodule/bcm_interface.h
@@ -437,6 +437,196 @@
     CBB *out, const struct BCM_mldsa87_private_key *private_key);
 
 
+// ML-KEM
+//
+// Where not commented, these functions have the same signature as the
+// corresponding public function.
+
+// BCM_MLKEM_ENCAP_ENTROPY is the number of bytes of uniformly random entropy
+// necessary to encapsulate a secret. The entropy will be leaked to the
+// decapsulating party.
+#define BCM_MLKEM_ENCAP_ENTROPY 32
+
+// BCM_MLKEM768_PUBLIC_KEY_BYTES is the number of bytes in an encoded ML-KEM-768
+// public key.
+#define BCM_MLKEM768_PUBLIC_KEY_BYTES 1184
+
+// BCM_MLKEM1024_PUBLIC_KEY_BYTES is the number of bytes in an encoded
+// ML-KEM-1024 public key.
+#define BCM_MLKEM1024_PUBLIC_KEY_BYTES 1568
+
+// BCM_MLKEM768_CIPHERTEXT_BYTES is number of bytes in the ML-KEM-768
+// ciphertext.
+#define BCM_MLKEM768_CIPHERTEXT_BYTES 1088
+
+// BCM_MLKEM1024_CIPHERTEXT_BYTES is number of bytes in the ML-KEM-1024
+// ciphertext.
+#define BCM_MLKEM1024_CIPHERTEXT_BYTES 1568
+
+// BCM_MLKEM768_PRIVATE_KEY_BYTES is the length of the data produced by
+// |BCM_mlkem768_marshal_private_key|.
+#define BCM_MLKEM768_PRIVATE_KEY_BYTES 2400
+
+// BCM_MLKEM1024_PRIVATE_KEY_BYTES is the length of the data produced by
+// |BCM_mlkem1024_marshal_private_key|.
+#define BCM_MLKEM1024_PRIVATE_KEY_BYTES 3168
+
+// BCM_MLKEM_SEED_BYTES is the number of bytes in an ML-KEM seed.
+#define BCM_MLKEM_SEED_BYTES 64
+
+// BCM_mlkem_SHARED_SECRET_BYTES is the number of bytes in an ML-KEM shared
+// secret.
+#define BCM_MLKEM_SHARED_SECRET_BYTES 32
+
+struct BCM_mlkem768_public_key {
+  union {
+    uint8_t bytes[512 * (3 + 9) + 32 + 32];
+    uint16_t alignment;
+  } opaque;
+};
+
+struct BCM_mlkem768_private_key {
+  union {
+    uint8_t bytes[512 * (3 + 3 + 9) + 32 + 32 + 32];
+    uint16_t alignment;
+  } opaque;
+};
+
+OPENSSL_EXPORT bcm_infallible BCM_mlkem768_generate_key(
+    uint8_t out_encoded_public_key[BCM_MLKEM768_PUBLIC_KEY_BYTES],
+    uint8_t optional_out_seed[BCM_MLKEM_SEED_BYTES],
+    struct BCM_mlkem768_private_key *out_private_key);
+
+OPENSSL_EXPORT bcm_status BCM_mlkem768_private_key_from_seed(
+    struct BCM_mlkem768_private_key *out_private_key, const uint8_t *seed,
+    size_t seed_len);
+
+OPENSSL_EXPORT bcm_infallible BCM_mlkem768_public_from_private(
+    struct BCM_mlkem768_public_key *out_public_key,
+    const struct BCM_mlkem768_private_key *private_key);
+
+OPENSSL_EXPORT bcm_infallible
+BCM_mlkem768_encap(uint8_t out_ciphertext[BCM_MLKEM768_CIPHERTEXT_BYTES],
+                   uint8_t out_shared_secret[BCM_MLKEM_SHARED_SECRET_BYTES],
+                   const struct BCM_mlkem768_public_key *public_key);
+
+OPENSSL_EXPORT bcm_status
+BCM_mlkem768_decap(uint8_t out_shared_secret[BCM_MLKEM_SHARED_SECRET_BYTES],
+                   const uint8_t *ciphertext, size_t ciphertext_len,
+                   const struct BCM_mlkem768_private_key *private_key);
+
+OPENSSL_EXPORT bcm_status BCM_mlkem768_marshal_public_key(
+    CBB *out, const struct BCM_mlkem768_public_key *public_key);
+
+OPENSSL_EXPORT bcm_status BCM_mlkem768_parse_public_key(
+    struct BCM_mlkem768_public_key *out_public_key, CBS *in);
+
+OPENSSL_EXPORT bcm_status BCM_mlkem768_parse_private_key(
+    struct BCM_mlkem768_private_key *out_private_key, CBS *in);
+
+// BCM_mlkem768_generate_key_external_seed is a deterministic function to create
+// a pair of ML-KEM-768 keys, using the supplied seed. The seed needs to be
+// uniformly random. This function should only be used for tests; regular
+// callers should use the non-deterministic |BCM_mlkem768_generate_key|
+// directly.
+OPENSSL_EXPORT bcm_infallible BCM_mlkem768_generate_key_external_seed(
+    uint8_t out_encoded_public_key[BCM_MLKEM768_PUBLIC_KEY_BYTES],
+    struct BCM_mlkem768_private_key *out_private_key,
+    const uint8_t seed[BCM_MLKEM_SEED_BYTES]);
+
+// BCM_mlkem768_encap_external_entropy behaves like |MLKEM768_encap|, but uses
+// |MLKEM_ENCAP_ENTROPY| bytes of |entropy| for randomization. The decapsulating
+// side will be able to recover |entropy| in full. This function should only be
+// used for tests, regular callers should use the non-deterministic
+// |BCM_mlkem768_encap| directly.
+OPENSSL_EXPORT bcm_infallible BCM_mlkem768_encap_external_entropy(
+    uint8_t out_ciphertext[BCM_MLKEM768_CIPHERTEXT_BYTES],
+    uint8_t out_shared_secret[BCM_MLKEM_SHARED_SECRET_BYTES],
+    const struct BCM_mlkem768_public_key *public_key,
+    const uint8_t entropy[BCM_MLKEM_ENCAP_ENTROPY]);
+
+// BCM_mlkem768_marshal_private_key serializes |private_key| to |out| in the
+// NIST format for ML-KEM-768 private keys. (Note that one can also save just
+// the seed value produced by |BCM_mlkem768_generate_key|, which is
+// significantly smaller.)
+OPENSSL_EXPORT bcm_status BCM_mlkem768_marshal_private_key(
+    CBB *out, const struct BCM_mlkem768_private_key *private_key);
+
+struct BCM_mlkem1024_public_key {
+  union {
+    uint8_t bytes[512 * (4 + 16) + 32 + 32];
+    uint16_t alignment;
+  } opaque;
+};
+
+struct BCM_mlkem1024_private_key {
+  union {
+    uint8_t bytes[512 * (4 + 4 + 16) + 32 + 32 + 32];
+    uint16_t alignment;
+  } opaque;
+};
+
+OPENSSL_EXPORT bcm_infallible BCM_mlkem1024_generate_key(
+    uint8_t out_encoded_public_key[BCM_MLKEM1024_PUBLIC_KEY_BYTES],
+    uint8_t optional_out_seed[BCM_MLKEM_SEED_BYTES],
+    struct BCM_mlkem1024_private_key *out_private_key);
+
+OPENSSL_EXPORT bcm_status BCM_mlkem1024_private_key_from_seed(
+    struct BCM_mlkem1024_private_key *out_private_key, const uint8_t *seed,
+    size_t seed_len);
+
+OPENSSL_EXPORT bcm_infallible BCM_mlkem1024_public_from_private(
+    struct BCM_mlkem1024_public_key *out_public_key,
+    const struct BCM_mlkem1024_private_key *private_key);
+
+OPENSSL_EXPORT bcm_infallible
+BCM_mlkem1024_encap(uint8_t out_ciphertext[BCM_MLKEM1024_CIPHERTEXT_BYTES],
+                    uint8_t out_shared_secret[BCM_MLKEM_SHARED_SECRET_BYTES],
+                    const struct BCM_mlkem1024_public_key *public_key);
+
+OPENSSL_EXPORT bcm_status
+BCM_mlkem1024_decap(uint8_t out_shared_secret[BCM_MLKEM_SHARED_SECRET_BYTES],
+                    const uint8_t *ciphertext, size_t ciphertext_len,
+                    const struct BCM_mlkem1024_private_key *private_key);
+
+OPENSSL_EXPORT bcm_status BCM_mlkem1024_marshal_public_key(
+    CBB *out, const struct BCM_mlkem1024_public_key *public_key);
+
+OPENSSL_EXPORT bcm_status BCM_mlkem1024_parse_public_key(
+    struct BCM_mlkem1024_public_key *out_public_key, CBS *in);
+
+OPENSSL_EXPORT bcm_status BCM_mlkem1024_parse_private_key(
+    struct BCM_mlkem1024_private_key *out_private_key, CBS *in);
+
+// BCM_mlkem1024_generate_key_external_seed is a deterministic function to
+// create a pair of ML-KEM-1024 keys, using the supplied seed. The seed needs to
+// be uniformly random. This function should only be used for tests, regular
+// callers should use the non-deterministic |BCM_mlkem1024_generate_key|
+// directly.
+OPENSSL_EXPORT bcm_infallible BCM_mlkem1024_generate_key_external_seed(
+    uint8_t out_encoded_public_key[BCM_MLKEM1024_PUBLIC_KEY_BYTES],
+    struct BCM_mlkem1024_private_key *out_private_key,
+    const uint8_t seed[BCM_MLKEM_SEED_BYTES]);
+
+// BCM_mlkem1024_encap_external_entropy behaves like |MLKEM1024_encap|, but uses
+// |MLKEM_ENCAP_ENTROPY| bytes of |entropy| for randomization. The
+// decapsulating side will be able to recover |entropy| in full. This function
+// should only be used for tests, regular callers should use the
+// non-deterministic |BCM_mlkem1024_encap| directly.
+OPENSSL_EXPORT bcm_infallible BCM_mlkem1024_encap_external_entropy(
+    uint8_t out_ciphertext[BCM_MLKEM1024_CIPHERTEXT_BYTES],
+    uint8_t out_shared_secret[BCM_MLKEM_SHARED_SECRET_BYTES],
+    const struct BCM_mlkem1024_public_key *public_key,
+    const uint8_t entropy[BCM_MLKEM_ENCAP_ENTROPY]);
+
+// BCM_mlkem1024_marshal_private_key serializes |private_key| to |out| in the
+// NIST format for ML-KEM-1024 private keys. (Note that one can also save just
+// the seed value produced by |BCM_mlkem1024_generate_key|, which is
+// significantly smaller.)
+OPENSSL_EXPORT bcm_status BCM_mlkem1024_marshal_private_key(
+    CBB *out, const struct BCM_mlkem1024_private_key *private_key);
+
+
 #if defined(__cplusplus)
 }  // extern C
 #endif
diff --git a/crypto/fipsmodule/mlkem/mlkem.cc.inc b/crypto/fipsmodule/mlkem/mlkem.cc.inc
new file mode 100644
index 0000000..ec6d484
--- /dev/null
+++ b/crypto/fipsmodule/mlkem/mlkem.cc.inc
@@ -0,0 +1,1142 @@
+/* Copyright 2014 The BoringSSL Authors
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+ * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+ * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+ * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
+
+#include <openssl/base.h>
+
+#include <assert.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <openssl/base.h>
+#include <openssl/bytestring.h>
+#include <openssl/mem.h>
+#include <openssl/rand.h>
+
+#include "../../internal.h"
+#include "../bcm_interface.h"
+#include "../keccak/internal.h"
+
+
+namespace mlkem {
+namespace {
+
+// See
+// https://csrc.nist.gov/pubs/fips/203/final
+
+static void prf(uint8_t *out, size_t out_len, const uint8_t in[33]) {
+  BORINGSSL_keccak(out, out_len, in, 33, boringssl_shake256);
+}
+
+// Section 4.1
+void hash_h(uint8_t out[32], const uint8_t *in, size_t len) {
+  BORINGSSL_keccak(out, 32, in, len, boringssl_sha3_256);
+}
+
+void hash_g(uint8_t out[64], const uint8_t *in, size_t len) {
+  BORINGSSL_keccak(out, 64, in, len, boringssl_sha3_512);
+}
+
+// This is called `J` in the spec.
+void kdf(uint8_t out[BCM_MLKEM_SHARED_SECRET_BYTES],
+         const uint8_t failure_secret[32], const uint8_t *ciphertext,
+         size_t ciphertext_len) {
+  struct BORINGSSL_keccak_st st;
+  BORINGSSL_keccak_init(&st, boringssl_shake256);
+  BORINGSSL_keccak_absorb(&st, failure_secret, 32);
+  BORINGSSL_keccak_absorb(&st, ciphertext, ciphertext_len);
+  BORINGSSL_keccak_squeeze(&st, out, BCM_MLKEM_SHARED_SECRET_BYTES);
+}
+
+// Constants that are common across all sizes.
+#define DEGREE 256
+const size_t kBarrettMultiplier = 5039;
+const unsigned kBarrettShift = 24;
+static const uint16_t kPrime = 3329;
+const int kLog2Prime = 12;
+const uint16_t kHalfPrime = (/*kPrime=*/3329 - 1) / 2;
+// kInverseDegree is 128^-1 mod 3329; 128 because kPrime does not have a 512th
+// root of unity.
+const uint16_t kInverseDegree = 3303;
+
+// Rank-specific constants.
+#define RANK768 3
+static const int kDU768 = 10;
+const int kDV768 = 4;
+#define RANK1024 4
+static const int kDU1024 = 11;
+const int kDV1024 = 5;
+
+constexpr size_t encoded_vector_size(int rank) {
+  return (kLog2Prime * DEGREE / 8) * static_cast<size_t>(rank);
+}
+
+constexpr size_t encoded_public_key_size(int rank) {
+  return encoded_vector_size(rank) + /*sizeof(rho)=*/32;
+}
+
+static_assert(encoded_public_key_size(RANK768) == BCM_MLKEM768_PUBLIC_KEY_BYTES,
+              "");
+static_assert(encoded_public_key_size(RANK1024) ==
+                  BCM_MLKEM1024_PUBLIC_KEY_BYTES,
+              "");
+
+constexpr size_t compressed_vector_size(int rank) {
+  // `if constexpr` isn't available in C++17.
+  return (rank == RANK768 ? kDU768 : kDU1024) * static_cast<size_t>(rank) *
+         DEGREE / 8;
+}
+
+constexpr size_t ciphertext_size(int rank) {
+  return compressed_vector_size(rank) +
+         (rank == RANK768 ? kDV768 : kDV1024) * DEGREE / 8;
+}
+
+static_assert(ciphertext_size(RANK768) == BCM_MLKEM768_CIPHERTEXT_BYTES, "");
+static_assert(ciphertext_size(RANK1024) == BCM_MLKEM1024_CIPHERTEXT_BYTES, "");
+
+typedef struct scalar {
+  // On every function entry and exit, 0 <= c < kPrime.
+  uint16_t c[DEGREE];
+} scalar;
+
+template <int RANK>
+struct vector {
+  scalar v[RANK];
+};
+
+template <int RANK>
+struct matrix {
+  scalar v[RANK][RANK];
+};
+
+// This bit of Python will be referenced in some of the following comments:
+//
+// p = 3329
+//
+// def bitreverse(i):
+//     ret = 0
+//     for n in range(7):
+//         bit = i & 1
+//         ret <<= 1
+//         ret |= bit
+//         i >>= 1
+//     return ret
+
+// kNTTRoots = [pow(17, bitreverse(i), p) for i in range(128)]
+const uint16_t kNTTRoots[128] = {
+    1,    1729, 2580, 3289, 2642, 630,  1897, 848,  1062, 1919, 193,  797,
+    2786, 3260, 569,  1746, 296,  2447, 1339, 1476, 3046, 56,   2240, 1333,
+    1426, 2094, 535,  2882, 2393, 2879, 1974, 821,  289,  331,  3253, 1756,
+    1197, 2304, 2277, 2055, 650,  1977, 2513, 632,  2865, 33,   1320, 1915,
+    2319, 1435, 807,  452,  1438, 2868, 1534, 2402, 2647, 2617, 1481, 648,
+    2474, 3110, 1227, 910,  17,   2761, 583,  2649, 1637, 723,  2288, 1100,
+    1409, 2662, 3281, 233,  756,  2156, 3015, 3050, 1703, 1651, 2789, 1789,
+    1847, 952,  1461, 2687, 939,  2308, 2437, 2388, 733,  2337, 268,  641,
+    1584, 2298, 2037, 3220, 375,  2549, 2090, 1645, 1063, 319,  2773, 757,
+    2099, 561,  2466, 2594, 2804, 1092, 403,  1026, 1143, 2150, 2775, 886,
+    1722, 1212, 1874, 1029, 2110, 2935, 885,  2154,
+};
+
+// kInverseNTTRoots = [pow(17, -bitreverse(i), p) for i in range(128)]
+const uint16_t kInverseNTTRoots[128] = {
+    1,    1600, 40,   749,  2481, 1432, 2699, 687,  1583, 2760, 69,   543,
+    2532, 3136, 1410, 2267, 2508, 1355, 450,  936,  447,  2794, 1235, 1903,
+    1996, 1089, 3273, 283,  1853, 1990, 882,  3033, 2419, 2102, 219,  855,
+    2681, 1848, 712,  682,  927,  1795, 461,  1891, 2877, 2522, 1894, 1010,
+    1414, 2009, 3296, 464,  2697, 816,  1352, 2679, 1274, 1052, 1025, 2132,
+    1573, 76,   2998, 3040, 1175, 2444, 394,  1219, 2300, 1455, 2117, 1607,
+    2443, 554,  1179, 2186, 2303, 2926, 2237, 525,  735,  863,  2768, 1230,
+    2572, 556,  3010, 2266, 1684, 1239, 780,  2954, 109,  1292, 1031, 1745,
+    2688, 3061, 992,  2596, 941,  892,  1021, 2390, 642,  1868, 2377, 1482,
+    1540, 540,  1678, 1626, 279,  314,  1173, 2573, 3096, 48,   667,  1920,
+    2229, 1041, 2606, 1692, 680,  2746, 568,  3312,
+};
+
+// kModRoots = [pow(17, 2*bitreverse(i) + 1, p) for i in range(128)]
+const uint16_t kModRoots[128] = {
+    17,   3312, 2761, 568,  583,  2746, 2649, 680,  1637, 1692, 723,  2606,
+    2288, 1041, 1100, 2229, 1409, 1920, 2662, 667,  3281, 48,   233,  3096,
+    756,  2573, 2156, 1173, 3015, 314,  3050, 279,  1703, 1626, 1651, 1678,
+    2789, 540,  1789, 1540, 1847, 1482, 952,  2377, 1461, 1868, 2687, 642,
+    939,  2390, 2308, 1021, 2437, 892,  2388, 941,  733,  2596, 2337, 992,
+    268,  3061, 641,  2688, 1584, 1745, 2298, 1031, 2037, 1292, 3220, 109,
+    375,  2954, 2549, 780,  2090, 1239, 1645, 1684, 1063, 2266, 319,  3010,
+    2773, 556,  757,  2572, 2099, 1230, 561,  2768, 2466, 863,  2594, 735,
+    2804, 525,  1092, 2237, 403,  2926, 1026, 2303, 1143, 2186, 2150, 1179,
+    2775, 554,  886,  2443, 1722, 1607, 1212, 2117, 1874, 1455, 1029, 2300,
+    2110, 1219, 2935, 394,  885,  2444, 2154, 1175,
+};
+
+// reduce_once reduces 0 <= x < 2*kPrime, mod kPrime.
+uint16_t reduce_once(uint16_t x) {
+  assert(x < 2 * kPrime);
+  const uint16_t subtracted = x - kPrime;
+  uint16_t mask = 0u - (subtracted >> 15);
+  // On Aarch64, omitting a |value_barrier_u16| results in a 2x speedup of
+  // ML-KEM overall and Clang still produces constant-time code using `csel`. On
+  // other platforms & compilers on godbolt that we care about, this code also
+  // produces constant-time output.
+  return (mask & x) | (~mask & subtracted);
+}
+
+// constant time reduce x mod kPrime using Barrett reduction. x must be less
+// than kPrime + 2×kPrime².
+static uint16_t reduce(uint32_t x) {
+  assert(x < kPrime + 2u * kPrime * kPrime);
+  uint64_t product = (uint64_t)x * kBarrettMultiplier;
+  uint32_t quotient = (uint32_t)(product >> kBarrettShift);
+  uint32_t remainder = x - quotient * kPrime;
+  return reduce_once(remainder);
+}
+
+void scalar_zero(scalar *out) { OPENSSL_memset(out, 0, sizeof(*out)); }
+
+template <int RANK>
+void vector_zero(vector<RANK> *out) {
+  OPENSSL_memset(out->v, 0, sizeof(scalar) * RANK);
+}
+
+// In place number theoretic transform of a given scalar.
+// Note that MLKEM's kPrime 3329 does not have a 512th root of unity, so this
+// transform leaves off the last iteration of the usual FFT code, with the 128
+// relevant roots of unity being stored in |kNTTRoots|. This means the output
+// should be seen as 128 elements in GF(3329^2), with the coefficients of the
+// elements being consecutive entries in |s->c|.
+static void scalar_ntt(scalar *s) {
+  int offset = DEGREE;
+  // `int` is used here because using `size_t` throughout caused a ~5% slowdown
+  // with Clang 14 on Aarch64.
+  for (int step = 1; step < DEGREE / 2; step <<= 1) {
+    offset >>= 1;
+    int k = 0;
+    for (int i = 0; i < step; i++) {
+      const uint32_t step_root = kNTTRoots[i + step];
+      for (int j = k; j < k + offset; j++) {
+        uint16_t odd = reduce(step_root * s->c[j + offset]);
+        uint16_t even = s->c[j];
+        s->c[j] = reduce_once(odd + even);
+        s->c[j + offset] = reduce_once(even - odd + kPrime);
+      }
+      k += 2 * offset;
+    }
+  }
+}
+
+template <int RANK>
+static void vector_ntt(vector<RANK> *a) {
+  for (int i = 0; i < RANK; i++) {
+    scalar_ntt(&a->v[i]);
+  }
+}
+
+// In place inverse number theoretic transform of a given scalar, with pairs of
+// entries of s->v being interpreted as elements of GF(3329^2). Just as with the
+// number theoretic transform, this leaves off the first step of the normal iFFT
+// to account for the fact that 3329 does not have a 512th root of unity, using
+// the precomputed 128 roots of unity stored in |kInverseNTTRoots|.
+void scalar_inverse_ntt(scalar *s) {
+  int step = DEGREE / 2;
+  // `int` is used here because using `size_t` throughout caused a ~5% slowdown
+  // with Clang 14 on Aarch64.
+  for (int offset = 2; offset < DEGREE; offset <<= 1) {
+    step >>= 1;
+    int k = 0;
+    for (int i = 0; i < step; i++) {
+      uint32_t step_root = kInverseNTTRoots[i + step];
+      for (int j = k; j < k + offset; j++) {
+        uint16_t odd = s->c[j + offset];
+        uint16_t even = s->c[j];
+        s->c[j] = reduce_once(odd + even);
+        s->c[j + offset] = reduce(step_root * (even - odd + kPrime));
+      }
+      k += 2 * offset;
+    }
+  }
+  for (int i = 0; i < DEGREE; i++) {
+    s->c[i] = reduce(s->c[i] * kInverseDegree);
+  }
+}
+
+template <int RANK>
+void vector_inverse_ntt(vector<RANK> *a) {
+  for (int i = 0; i < RANK; i++) {
+    scalar_inverse_ntt(&a->v[i]);
+  }
+}
+
+void scalar_add(scalar *lhs, const scalar *rhs) {
+  for (int i = 0; i < DEGREE; i++) {
+    lhs->c[i] = reduce_once(lhs->c[i] + rhs->c[i]);
+  }
+}
+
+void scalar_sub(scalar *lhs, const scalar *rhs) {
+  for (int i = 0; i < DEGREE; i++) {
+    lhs->c[i] = reduce_once(lhs->c[i] - rhs->c[i] + kPrime);
+  }
+}
+
+// Multiplying two scalars in the number theoretically transformed state. Since
+// 3329 does not have a 512th root of unity, this means we have to interpret
+// the 2*ith and (2*i+1)th entries of the scalar as elements of GF(3329)[X]/(X^2
+// - 17^(2*bitreverse(i)+1)) The value of 17^(2*bitreverse(i)+1) mod 3329 is
+// stored in the precomputed |kModRoots| table. Note that our Barrett transform
+// only allows us to multipy two reduced numbers together, so we need some
+// intermediate reduction steps, even if an uint64_t could hold 3 multiplied
+// numbers.
+void scalar_mult(scalar *out, const scalar *lhs, const scalar *rhs) {
+  for (int i = 0; i < DEGREE / 2; i++) {
+    uint32_t real_real = (uint32_t)lhs->c[2 * i] * rhs->c[2 * i];
+    uint32_t img_img = (uint32_t)lhs->c[2 * i + 1] * rhs->c[2 * i + 1];
+    uint32_t real_img = (uint32_t)lhs->c[2 * i] * rhs->c[2 * i + 1];
+    uint32_t img_real = (uint32_t)lhs->c[2 * i + 1] * rhs->c[2 * i];
+    out->c[2 * i] =
+        reduce(real_real + (uint32_t)reduce(img_img) * kModRoots[i]);
+    out->c[2 * i + 1] = reduce(img_real + real_img);
+  }
+}
+
+template <int RANK>
+void vector_add(vector<RANK> *lhs, const vector<RANK> *rhs) {
+  for (int i = 0; i < RANK; i++) {
+    scalar_add(&lhs->v[i], &rhs->v[i]);
+  }
+}
+
+template <int RANK>
+static void matrix_mult(vector<RANK> *out, const matrix<RANK> *m,
+                        const vector<RANK> *a) {
+  vector_zero(out);
+  for (int i = 0; i < RANK; i++) {
+    for (int j = 0; j < RANK; j++) {
+      scalar product;
+      scalar_mult(&product, &m->v[i][j], &a->v[j]);
+      scalar_add(&out->v[i], &product);
+    }
+  }
+}
+
+template <int RANK>
+void matrix_mult_transpose(vector<RANK> *out, const matrix<RANK> *m,
+                           const vector<RANK> *a) {
+  vector_zero(out);
+  for (int i = 0; i < RANK; i++) {
+    for (int j = 0; j < RANK; j++) {
+      scalar product;
+      scalar_mult(&product, &m->v[j][i], &a->v[j]);
+      scalar_add(&out->v[i], &product);
+    }
+  }
+}
+
+template <int RANK>
+void scalar_inner_product(scalar *out, const vector<RANK> *lhs,
+                          const vector<RANK> *rhs) {
+  scalar_zero(out);
+  for (int i = 0; i < RANK; i++) {
+    scalar product;
+    scalar_mult(&product, &lhs->v[i], &rhs->v[i]);
+    scalar_add(out, &product);
+  }
+}
+
+// Algorithm 6 from the spec. Rejection samples a Keccak stream to get
+// uniformly distributed elements. This is used for matrix expansion and only
+// operates on public inputs.
+static void scalar_from_keccak_vartime(scalar *out,
+                                       struct BORINGSSL_keccak_st *keccak_ctx) {
+  assert(keccak_ctx->squeeze_offset == 0);
+  assert(keccak_ctx->rate_bytes == 168);
+  static_assert(168 % 3 == 0, "block and coefficient boundaries do not align");
+
+  int done = 0;
+  while (done < DEGREE) {
+    uint8_t block[168];
+    BORINGSSL_keccak_squeeze(keccak_ctx, block, sizeof(block));
+    for (size_t i = 0; i < sizeof(block) && done < DEGREE; i += 3) {
+      uint16_t d1 = block[i] + 256 * (block[i + 1] % 16);
+      uint16_t d2 = block[i + 1] / 16 + 16 * block[i + 2];
+      if (d1 < kPrime) {
+        out->c[done++] = d1;
+      }
+      if (d2 < kPrime && done < DEGREE) {
+        out->c[done++] = d2;
+      }
+    }
+  }
+}
+
+// Algorithm 7 from the spec, with eta fixed to two and the PRF call
+// included. Creates binominally distributed elements by sampling 2*|eta| bits,
+// and setting the coefficient to the count of the first bits minus the count of
+// the second bits, resulting in a centered binomial distribution. Since eta is
+// two this gives -2/2 with a probability of 1/16, -1/1 with probability 1/4,
+// and 0 with probability 3/8.
+void scalar_centered_binomial_distribution_eta_2_with_prf(
+    scalar *out, const uint8_t input[33]) {
+  uint8_t entropy[128];
+  static_assert(sizeof(entropy) == 2 * /*kEta=*/2 * DEGREE / 8, "");
+  prf(entropy, sizeof(entropy), input);
+
+  for (int i = 0; i < DEGREE; i += 2) {
+    uint8_t byte = entropy[i / 2];
+
+    uint16_t value = kPrime;
+    value += (byte & 1) + ((byte >> 1) & 1);
+    value -= ((byte >> 2) & 1) + ((byte >> 3) & 1);
+    out->c[i] = reduce_once(value);
+
+    byte >>= 4;
+    value = kPrime;
+    value += (byte & 1) + ((byte >> 1) & 1);
+    value -= ((byte >> 2) & 1) + ((byte >> 3) & 1);
+    out->c[i + 1] = reduce_once(value);
+  }
+}
+
+// Generates a secret vector by using
+// |scalar_centered_binomial_distribution_eta_2_with_prf|, using the given seed
+// appending and incrementing |counter| for entry of the vector.
+template <int RANK>
+void vector_generate_secret_eta_2(vector<RANK> *out, uint8_t *counter,
+                                  const uint8_t seed[32]) {
+  uint8_t input[33];
+  OPENSSL_memcpy(input, seed, 32);
+  for (int i = 0; i < RANK; i++) {
+    input[32] = (*counter)++;
+    scalar_centered_binomial_distribution_eta_2_with_prf(&out->v[i], input);
+  }
+}
+
+// Expands the matrix of a seed for key generation and for encaps-CPA.
+template <int RANK>
+void matrix_expand(matrix<RANK> *out, const uint8_t rho[32]) {
+  uint8_t input[34];
+  OPENSSL_memcpy(input, rho, 32);
+  for (int i = 0; i < RANK; i++) {
+    for (int j = 0; j < RANK; j++) {
+      input[32] = i;
+      input[33] = j;
+      struct BORINGSSL_keccak_st keccak_ctx;
+      BORINGSSL_keccak_init(&keccak_ctx, boringssl_shake128);
+      BORINGSSL_keccak_absorb(&keccak_ctx, input, sizeof(input));
+      scalar_from_keccak_vartime(&out->v[i][j], &keccak_ctx);
+    }
+  }
+}
+
+const uint8_t kMasks[8] = {0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f, 0xff};
+
+void scalar_encode(uint8_t *out, const scalar *s, int bits) {
+  assert(bits <= (int)sizeof(*s->c) * 8 && bits != 1);
+
+  uint8_t out_byte = 0;
+  int out_byte_bits = 0;
+
+  for (int i = 0; i < DEGREE; i++) {
+    uint16_t element = s->c[i];
+    int element_bits_done = 0;
+
+    while (element_bits_done < bits) {
+      int chunk_bits = bits - element_bits_done;
+      int out_bits_remaining = 8 - out_byte_bits;
+      if (chunk_bits >= out_bits_remaining) {
+        chunk_bits = out_bits_remaining;
+        out_byte |= (element & kMasks[chunk_bits - 1]) << out_byte_bits;
+        *out = out_byte;
+        out++;
+        out_byte_bits = 0;
+        out_byte = 0;
+      } else {
+        out_byte |= (element & kMasks[chunk_bits - 1]) << out_byte_bits;
+        out_byte_bits += chunk_bits;
+      }
+
+      element_bits_done += chunk_bits;
+      element >>= chunk_bits;
+    }
+  }
+
+  if (out_byte_bits > 0) {
+    *out = out_byte;
+  }
+}
+
+// scalar_encode_1 is |scalar_encode| specialised for |bits| == 1.
+void scalar_encode_1(uint8_t out[32], const scalar *s) {
+  for (int i = 0; i < DEGREE; i += 8) {
+    uint8_t out_byte = 0;
+    for (int j = 0; j < 8; j++) {
+      out_byte |= (s->c[i + j] & 1) << j;
+    }
+    *out = out_byte;
+    out++;
+  }
+}
+
+// Encodes an entire vector into 32*|RANK|*|bits| bytes. Note that since 256
+// (DEGREE) is divisible by 8, the individual vector entries will always fill a
+// whole number of bytes, so we do not need to worry about bit packing here.
+template <int RANK>
+void vector_encode(uint8_t *out, const vector<RANK> *a, int bits) {
+  for (int i = 0; i < RANK; i++) {
+    scalar_encode(out + i * bits * DEGREE / 8, &a->v[i], bits);
+  }
+}
+
+// scalar_decode parses |DEGREE * bits| bits from |in| into |DEGREE| values in
+// |out|. It returns one on success and zero if any parsed value is >=
+// |kPrime|.
+int scalar_decode(scalar *out, const uint8_t *in, int bits) {
+  assert(bits <= (int)sizeof(*out->c) * 8 && bits != 1);
+
+  uint8_t in_byte = 0;
+  int in_byte_bits_left = 0;
+
+  for (int i = 0; i < DEGREE; i++) {
+    uint16_t element = 0;
+    int element_bits_done = 0;
+
+    while (element_bits_done < bits) {
+      if (in_byte_bits_left == 0) {
+        in_byte = *in;
+        in++;
+        in_byte_bits_left = 8;
+      }
+
+      int chunk_bits = bits - element_bits_done;
+      if (chunk_bits > in_byte_bits_left) {
+        chunk_bits = in_byte_bits_left;
+      }
+
+      element |= (in_byte & kMasks[chunk_bits - 1]) << element_bits_done;
+      in_byte_bits_left -= chunk_bits;
+      in_byte >>= chunk_bits;
+
+      element_bits_done += chunk_bits;
+    }
+
+    if (element >= kPrime) {
+      return 0;
+    }
+    out->c[i] = element;
+  }
+
+  return 1;
+}
+
+// scalar_decode_1 is |scalar_decode| specialised for |bits| == 1.
+void scalar_decode_1(scalar *out, const uint8_t in[32]) {
+  for (int i = 0; i < DEGREE; i += 8) {
+    uint8_t in_byte = *in;
+    in++;
+    for (int j = 0; j < 8; j++) {
+      out->c[i + j] = in_byte & 1;
+      in_byte >>= 1;
+    }
+  }
+}
+
+// Decodes 32*|RANK|*|bits| bytes from |in| into |out|. It returns one on
+// success or zero if any parsed value is >= |kPrime|.
+template <int RANK>
+static int vector_decode(vector<RANK> *out, const uint8_t *in, int bits) {
+  for (int i = 0; i < RANK; i++) {
+    if (!scalar_decode(&out->v[i], in + i * bits * DEGREE / 8, bits)) {
+      return 0;
+    }
+  }
+  return 1;
+}
+
+// Compresses (lossily) an input |x| mod 3329 into |bits| many bits by grouping
+// numbers close to each other together. The formula used is
+// round(2^|bits|/kPrime*x) mod 2^|bits|.
+// Uses Barrett reduction to achieve constant time. Since we need both the
+// remainder (for rounding) and the quotient (as the result), we cannot use
+// |reduce| here, but need to do the Barrett reduction directly.
+static uint16_t compress(uint16_t x, int bits) {
+  uint32_t shifted = (uint32_t)x << bits;
+  uint64_t product = (uint64_t)shifted * kBarrettMultiplier;
+  uint32_t quotient = (uint32_t)(product >> kBarrettShift);
+  uint32_t remainder = shifted - quotient * kPrime;
+
+  // Adjust the quotient to round correctly:
+  //   0 <= remainder <= kHalfPrime round to 0
+  //   kHalfPrime < remainder <= kPrime + kHalfPrime round to 1
+  //   kPrime + kHalfPrime < remainder < 2 * kPrime round to 2
+  assert(remainder < 2u * kPrime);
+  quotient += 1 & constant_time_lt_w(kHalfPrime, remainder);
+  quotient += 1 & constant_time_lt_w(kPrime + kHalfPrime, remainder);
+  return quotient & ((1 << bits) - 1);
+}
+
+// Decompresses |x| by using an equi-distant representative. The formula is
+// round(kPrime/2^|bits|*x). Note that 2^|bits| being the divisor allows us to
+// implement this logic using only bit operations.
+uint16_t decompress(uint16_t x, int bits) {
+  uint32_t product = (uint32_t)x * kPrime;
+  uint32_t power = 1 << bits;
+  // This is |product| % power, since |power| is a power of 2.
+  uint32_t remainder = product & (power - 1);
+  // This is |product| / power, since |power| is a power of 2.
+  uint32_t lower = product >> bits;
+  // The rounding logic works since the first half of numbers mod |power| have a
+  // 0 as first bit, and the second half has a 1 as first bit, since |power| is
+  // a power of 2. As a 12 bit number, |remainder| is always positive, so we
+  // will shift in 0s for a right shift.
+  return lower + (remainder >> (bits - 1));
+}
+
+static void scalar_compress(scalar *s, int bits) {
+  for (int i = 0; i < DEGREE; i++) {
+    s->c[i] = compress(s->c[i], bits);
+  }
+}
+
+static void scalar_decompress(scalar *s, int bits) {
+  for (int i = 0; i < DEGREE; i++) {
+    s->c[i] = decompress(s->c[i], bits);
+  }
+}
+
+template <int RANK>
+void vector_compress(vector<RANK> *a, int bits) {
+  for (int i = 0; i < RANK; i++) {
+    scalar_compress(&a->v[i], bits);
+  }
+}
+
+template <int RANK>
+void vector_decompress(vector<RANK> *a, int bits) {
+  for (int i = 0; i < RANK; i++) {
+    scalar_decompress(&a->v[i], bits);
+  }
+}
+
+template <int RANK>
+struct public_key {
+  vector<RANK> t;
+  uint8_t rho[32];
+  uint8_t public_key_hash[32];
+  matrix<RANK> m;
+};
+
+template <int RANK>
+struct private_key {
+  struct public_key<RANK> pub;
+  vector<RANK> s;
+  uint8_t fo_failure_secret[32];
+};
+
+template <int RANK>
+static void decrypt_cpa(
+    uint8_t out[32], const struct private_key<RANK> *priv,
+    const uint8_t ciphertext[BCM_MLKEM768_CIPHERTEXT_BYTES]) {
+  constexpr int du = RANK == RANK768 ? kDU768 : kDU1024;
+  constexpr int dv = RANK == RANK768 ? kDV768 : kDV1024;
+
+  vector<RANK> u;
+  vector_decode(&u, ciphertext, du);
+  vector_decompress(&u, du);
+  vector_ntt(&u);
+  scalar v;
+  scalar_decode(&v, ciphertext + compressed_vector_size(RANK), dv);
+  scalar_decompress(&v, dv);
+  scalar mask;
+  scalar_inner_product(&mask, &priv->s, &u);
+  scalar_inverse_ntt(&mask);
+  scalar_sub(&v, &mask);
+  scalar_compress(&v, 1);
+  scalar_encode_1(out, &v);
+}
+
+template <int RANK>
+static bcm_status mlkem_marshal_public_key(CBB *out,
+                                           const struct public_key<RANK> *pub) {
+  uint8_t *vector_output;
+  if (!CBB_add_space(out, &vector_output, encoded_vector_size(RANK))) {
+    return bcm_status::failure;
+  }
+  vector_encode(vector_output, &pub->t, kLog2Prime);
+  if (!CBB_add_bytes(out, pub->rho, sizeof(pub->rho))) {
+    return bcm_status::failure;
+  }
+  return bcm_status::approved;
+}
+
+template <int RANK>
+void mlkem_generate_key_external_seed(
+    uint8_t *out_encoded_public_key, private_key<RANK> *priv,
+    const uint8_t seed[BCM_MLKEM_SEED_BYTES]) {
+  uint8_t augmented_seed[33];
+  OPENSSL_memcpy(augmented_seed, seed, 32);
+  augmented_seed[32] = RANK;
+
+  uint8_t hashed[64];
+  hash_g(hashed, augmented_seed, sizeof(augmented_seed));
+  const uint8_t *const rho = hashed;
+  const uint8_t *const sigma = hashed + 32;
+  OPENSSL_memcpy(priv->pub.rho, hashed, sizeof(priv->pub.rho));
+  matrix_expand(&priv->pub.m, rho);
+  uint8_t counter = 0;
+  vector_generate_secret_eta_2(&priv->s, &counter, sigma);
+  vector_ntt(&priv->s);
+  vector<RANK> error;
+  vector_generate_secret_eta_2(&error, &counter, sigma);
+  vector_ntt(&error);
+  matrix_mult_transpose(&priv->pub.t, &priv->pub.m, &priv->s);
+  vector_add(&priv->pub.t, &error);
+
+  CBB cbb;
+  CBB_init_fixed(&cbb, out_encoded_public_key, encoded_public_key_size(RANK));
+  if (!bcm_success(mlkem_marshal_public_key(&cbb, &priv->pub))) {
+    abort();
+  }
+
+  hash_h(priv->pub.public_key_hash, out_encoded_public_key,
+         encoded_public_key_size(RANK));
+  OPENSSL_memcpy(priv->fo_failure_secret, seed + 32, 32);
+}
+
+// Encrypts a message with given randomness to
+// the ciphertext in |out|. Without applying the Fujisaki-Okamoto transform this
+// would not result in a CCA secure scheme, since lattice schemes are vulnerable
+// to decryption failure oracles.
+template <int RANK>
+void encrypt_cpa(uint8_t *out, const struct mlkem::public_key<RANK> *pub,
+                 const uint8_t message[32], const uint8_t randomness[32]) {
+  constexpr int du = RANK == RANK768 ? mlkem::kDU768 : mlkem::kDU1024;
+  constexpr int dv = RANK == RANK768 ? mlkem::kDV768 : mlkem::kDV1024;
+
+  uint8_t counter = 0;
+  mlkem::vector<RANK> secret;
+  vector_generate_secret_eta_2(&secret, &counter, randomness);
+  vector_ntt(&secret);
+  mlkem::vector<RANK> error;
+  vector_generate_secret_eta_2(&error, &counter, randomness);
+  uint8_t input[33];
+  OPENSSL_memcpy(input, randomness, 32);
+  input[32] = counter;
+  mlkem::scalar scalar_error;
+  scalar_centered_binomial_distribution_eta_2_with_prf(&scalar_error, input);
+  mlkem::vector<RANK> u;
+  matrix_mult(&u, &pub->m, &secret);
+  vector_inverse_ntt(&u);
+  vector_add(&u, &error);
+  mlkem::scalar v;
+  scalar_inner_product(&v, &pub->t, &secret);
+  scalar_inverse_ntt(&v);
+  scalar_add(&v, &scalar_error);
+  mlkem::scalar expanded_message;
+  scalar_decode_1(&expanded_message, message);
+  scalar_decompress(&expanded_message, 1);
+  scalar_add(&v, &expanded_message);
+  vector_compress(&u, du);
+  vector_encode(out, &u, du);
+  scalar_compress(&v, dv);
+  scalar_encode(out + mlkem::compressed_vector_size(RANK), &v, dv);
+}
+
+// See section 6.3
+template <int RANK>
+void mlkem_decap(uint8_t out_shared_secret[BCM_MLKEM_SHARED_SECRET_BYTES],
+                 const uint8_t *ciphertext,
+                 const struct private_key<RANK> *priv) {
+  uint8_t decrypted[64];
+  decrypt_cpa(decrypted, priv, ciphertext);
+  OPENSSL_memcpy(decrypted + 32, priv->pub.public_key_hash,
+                 sizeof(decrypted) - 32);
+  uint8_t key_and_randomness[64];
+  hash_g(key_and_randomness, decrypted, sizeof(decrypted));
+  constexpr size_t ciphertext_len = ciphertext_size(RANK);
+  uint8_t expected_ciphertext[BCM_MLKEM1024_CIPHERTEXT_BYTES];
+  static_assert(ciphertext_len <= sizeof(expected_ciphertext), "");
+  encrypt_cpa(expected_ciphertext, &priv->pub, decrypted,
+              key_and_randomness + 32);
+
+  uint8_t failure_key[32];
+  kdf(failure_key, priv->fo_failure_secret, ciphertext, ciphertext_len);
+
+  uint8_t mask = constant_time_eq_int_8(
+      CRYPTO_memcmp(ciphertext, expected_ciphertext, ciphertext_len), 0);
+  for (int i = 0; i < BCM_MLKEM_SHARED_SECRET_BYTES; i++) {
+    out_shared_secret[i] =
+        constant_time_select_8(mask, key_and_randomness[i], failure_key[i]);
+  }
+}
+
+// mlkem_parse_public_key_no_hash parses |in| into |pub| but doesn't calculate
+// the value of |pub->public_key_hash|.
+template <int RANK>
+int mlkem_parse_public_key_no_hash(struct public_key<RANK> *pub, CBS *in) {
+  CBS t_bytes;
+  if (!CBS_get_bytes(in, &t_bytes, encoded_vector_size(RANK)) ||
+      !vector_decode(&pub->t, CBS_data(&t_bytes), kLog2Prime) ||
+      !CBS_copy_bytes(in, pub->rho, sizeof(pub->rho))) {
+    return 0;
+  }
+  matrix_expand(&pub->m, pub->rho);
+  return 1;
+}
+
+template <int RANK>
+int mlkem_parse_public_key(struct public_key<RANK> *pub, CBS *in) {
+  CBS orig_in = *in;
+  if (!mlkem_parse_public_key_no_hash(pub, in) ||  //
+      CBS_len(in) != 0) {
+    return 0;
+  }
+  hash_h(pub->public_key_hash, CBS_data(&orig_in), CBS_len(&orig_in));
+  return 1;
+}
+
+template <int RANK>
+int mlkem_parse_private_key(struct private_key<RANK> *priv, CBS *in) {
+  CBS s_bytes;
+  if (!CBS_get_bytes(in, &s_bytes, encoded_vector_size(RANK)) ||
+      !vector_decode(&priv->s, CBS_data(&s_bytes), kLog2Prime) ||
+      !mlkem_parse_public_key_no_hash(&priv->pub, in) ||
+      !CBS_copy_bytes(in, priv->pub.public_key_hash,
+                      sizeof(priv->pub.public_key_hash)) ||
+      !CBS_copy_bytes(in, priv->fo_failure_secret,
+                      sizeof(priv->fo_failure_secret)) ||
+      CBS_len(in) != 0) {
+    return 0;
+  }
+  return 1;
+}
+
+template <int RANK>
+int mlkem_marshal_private_key(CBB *out, const struct private_key<RANK> *priv) {
+  uint8_t *s_output;
+  if (!CBB_add_space(out, &s_output, encoded_vector_size(RANK))) {
+    return 0;
+  }
+  vector_encode(s_output, &priv->s, kLog2Prime);
+  if (!bcm_success(mlkem_marshal_public_key(out, &priv->pub)) ||
+      !CBB_add_bytes(out, priv->pub.public_key_hash,
+                     sizeof(priv->pub.public_key_hash)) ||
+      !CBB_add_bytes(out, priv->fo_failure_secret,
+                     sizeof(priv->fo_failure_secret))) {
+    return 0;
+  }
+  return 1;
+}
+
+struct public_key<RANK768> *public_key_768_from_external(
+    const struct BCM_mlkem768_public_key *external) {
+  static_assert(sizeof(struct BCM_mlkem768_public_key) >=
+                    sizeof(struct public_key<RANK768>),
+                "MLKEM public key is too small");
+  static_assert(alignof(struct BCM_mlkem768_public_key) >=
+                    alignof(struct public_key<RANK768>),
+                "MLKEM public key alignment incorrect");
+  return (struct public_key<RANK768> *)external;
+}
+
+static struct public_key<RANK1024> *
+public_key_1024_from_external(const struct BCM_mlkem1024_public_key *external) {
+  static_assert(sizeof(struct BCM_mlkem1024_public_key) >=
+                    sizeof(struct public_key<RANK1024>),
+                "MLKEM1024 public key is too small");
+  static_assert(alignof(struct BCM_mlkem1024_public_key) >=
+                    alignof(struct public_key<RANK1024>),
+                "MLKEM1024 public key alignment incorrect");
+  return (struct public_key<RANK1024> *)external;
+}
+
+struct private_key<RANK768> *
+private_key_768_from_external(const struct BCM_mlkem768_private_key *external) {
+  static_assert(sizeof(struct BCM_mlkem768_private_key) >=
+                    sizeof(struct private_key<RANK768>),
+                "MLKEM private key too small");
+  static_assert(alignof(struct BCM_mlkem768_private_key) >=
+                    alignof(struct private_key<RANK768>),
+                "MLKEM private key alignment incorrect");
+  return (struct private_key<RANK768> *)external;
+}
+
+struct private_key<RANK1024> *
+private_key_1024_from_external(
+    const struct BCM_mlkem1024_private_key *external) {
+  static_assert(sizeof(struct BCM_mlkem1024_private_key) >=
+                    sizeof(struct private_key<RANK1024>),
+                "MLKEM1024 private key too small");
+  static_assert(alignof(struct BCM_mlkem1024_private_key) >=
+                    alignof(struct private_key<RANK1024>),
+                "MLKEM1024 private key alignment incorrect");
+  return (struct private_key<RANK1024> *)external;
+}
+
+}  // namespace
+}  // namespace mlkem
+
+bcm_infallible BCM_mlkem768_generate_key(
+    uint8_t out_encoded_public_key[BCM_MLKEM768_PUBLIC_KEY_BYTES],
+    uint8_t optional_out_seed[BCM_MLKEM_SEED_BYTES],
+    struct BCM_mlkem768_private_key *out_private_key) {
+  uint8_t seed[BCM_MLKEM_SEED_BYTES];
+  RAND_bytes(seed, sizeof(seed));
+  if (optional_out_seed) {
+    OPENSSL_memcpy(optional_out_seed, seed, sizeof(seed));
+  }
+  BCM_mlkem768_generate_key_external_seed(out_encoded_public_key,
+                                          out_private_key, seed);
+  return bcm_infallible::approved;
+}
+
+bcm_status BCM_mlkem768_private_key_from_seed(
+    struct BCM_mlkem768_private_key *out_private_key, const uint8_t *seed,
+    size_t seed_len) {
+  if (seed_len != BCM_MLKEM_SEED_BYTES) {
+    return bcm_status::failure;
+  }
+  uint8_t public_key_bytes[BCM_MLKEM768_PUBLIC_KEY_BYTES];
+  BCM_mlkem768_generate_key_external_seed(public_key_bytes, out_private_key,
+                                          seed);
+  return bcm_status::approved;
+}
+
+bcm_infallible BCM_mlkem1024_generate_key(
+    uint8_t out_encoded_public_key[BCM_MLKEM1024_PUBLIC_KEY_BYTES],
+    uint8_t optional_out_seed[BCM_MLKEM_SEED_BYTES],
+    struct BCM_mlkem1024_private_key *out_private_key) {
+  uint8_t seed[BCM_MLKEM_SEED_BYTES];
+  RAND_bytes(seed, sizeof(seed));
+  if (optional_out_seed) {
+    OPENSSL_memcpy(optional_out_seed, seed, sizeof(seed));
+  }
+  BCM_mlkem1024_generate_key_external_seed(out_encoded_public_key,
+                                           out_private_key, seed);
+  return bcm_infallible::approved;
+}
+
+bcm_status BCM_mlkem1024_private_key_from_seed(
+    struct BCM_mlkem1024_private_key *out_private_key, const uint8_t *seed,
+    size_t seed_len) {
+  if (seed_len != BCM_MLKEM_SEED_BYTES) {
+    return bcm_status::failure;
+  }
+  uint8_t public_key_bytes[BCM_MLKEM1024_PUBLIC_KEY_BYTES];
+  BCM_mlkem1024_generate_key_external_seed(public_key_bytes, out_private_key,
+                                           seed);
+  return bcm_status::approved;
+}
+
+bcm_infallible BCM_mlkem768_generate_key_external_seed(
+    uint8_t out_encoded_public_key[BCM_MLKEM768_PUBLIC_KEY_BYTES],
+    struct BCM_mlkem768_private_key *out_private_key,
+    const uint8_t seed[BCM_MLKEM_SEED_BYTES]) {
+  mlkem::private_key<RANK768> *priv =
+      mlkem::private_key_768_from_external(out_private_key);
+  mlkem_generate_key_external_seed(out_encoded_public_key, priv, seed);
+  return bcm_infallible::approved;
+}
+
+bcm_infallible BCM_mlkem1024_generate_key_external_seed(
+    uint8_t out_encoded_public_key[BCM_MLKEM1024_PUBLIC_KEY_BYTES],
+    struct BCM_mlkem1024_private_key *out_private_key,
+    const uint8_t seed[BCM_MLKEM_SEED_BYTES]) {
+  mlkem::private_key<RANK1024> *priv =
+      mlkem::private_key_1024_from_external(out_private_key);
+  mlkem_generate_key_external_seed(out_encoded_public_key, priv, seed);
+  return bcm_infallible::approved;
+}
+
+bcm_infallible BCM_mlkem768_public_from_private(
+    struct BCM_mlkem768_public_key *out_public_key,
+    const struct BCM_mlkem768_private_key *private_key) {
+  struct mlkem::public_key<RANK768> *const pub =
+      mlkem::public_key_768_from_external(out_public_key);
+  const struct mlkem::private_key<RANK768> *const priv =
+      mlkem::private_key_768_from_external(private_key);
+  *pub = priv->pub;
+  return bcm_infallible::approved;
+}
+
+bcm_infallible BCM_mlkem1024_public_from_private(
+    struct BCM_mlkem1024_public_key *out_public_key,
+    const struct BCM_mlkem1024_private_key *private_key) {
+  struct mlkem::public_key<RANK1024> *const pub =
+      mlkem::public_key_1024_from_external(out_public_key);
+  const struct mlkem::private_key<RANK1024> *const priv =
+      mlkem::private_key_1024_from_external(private_key);
+  *pub = priv->pub;
+  return bcm_infallible::approved;
+}
+
+// Calls |MLKEM768_encap_external_entropy| with random bytes from |RAND_bytes|
+bcm_infallible BCM_mlkem768_encap(
+    uint8_t out_ciphertext[BCM_MLKEM768_CIPHERTEXT_BYTES],
+    uint8_t out_shared_secret[BCM_MLKEM_SHARED_SECRET_BYTES],
+    const struct BCM_mlkem768_public_key *public_key) {
+  uint8_t entropy[BCM_MLKEM_ENCAP_ENTROPY];
+  RAND_bytes(entropy, BCM_MLKEM_ENCAP_ENTROPY);
+  BCM_mlkem768_encap_external_entropy(out_ciphertext, out_shared_secret,
+                                      public_key, entropy);
+  return bcm_infallible::approved;
+}
+
+bcm_infallible BCM_mlkem1024_encap(
+    uint8_t out_ciphertext[BCM_MLKEM1024_CIPHERTEXT_BYTES],
+    uint8_t out_shared_secret[BCM_MLKEM_SHARED_SECRET_BYTES],
+    const struct BCM_mlkem1024_public_key *public_key) {
+  uint8_t entropy[BCM_MLKEM_ENCAP_ENTROPY];
+  RAND_bytes(entropy, BCM_MLKEM_ENCAP_ENTROPY);
+  BCM_mlkem1024_encap_external_entropy(out_ciphertext, out_shared_secret,
+                                       public_key, entropy);
+  return bcm_infallible::approved;
+}
+
+// See section 6.2.
+template <int RANK>
+void mlkem_encap_external_entropy(
+    uint8_t *out_ciphertext,
+    uint8_t out_shared_secret[BCM_MLKEM_SHARED_SECRET_BYTES],
+    const struct mlkem::public_key<RANK> *pub,
+    const uint8_t entropy[BCM_MLKEM_ENCAP_ENTROPY]) {
+  uint8_t input[64];
+  OPENSSL_memcpy(input, entropy, BCM_MLKEM_ENCAP_ENTROPY);
+  OPENSSL_memcpy(input + BCM_MLKEM_ENCAP_ENTROPY, pub->public_key_hash,
+                 sizeof(input) - BCM_MLKEM_ENCAP_ENTROPY);
+  uint8_t key_and_randomness[64];
+  mlkem::hash_g(key_and_randomness, input, sizeof(input));
+  encrypt_cpa(out_ciphertext, pub, entropy, key_and_randomness + 32);
+  static_assert(BCM_MLKEM_SHARED_SECRET_BYTES == 32, "");
+  memcpy(out_shared_secret, key_and_randomness, 32);
+}
+
+bcm_infallible BCM_mlkem768_encap_external_entropy(
+    uint8_t out_ciphertext[BCM_MLKEM768_CIPHERTEXT_BYTES],
+    uint8_t out_shared_secret[BCM_MLKEM_SHARED_SECRET_BYTES],
+    const struct BCM_mlkem768_public_key *public_key,
+    const uint8_t entropy[BCM_MLKEM_ENCAP_ENTROPY]) {
+  const struct mlkem::public_key<RANK768> *pub =
+      mlkem::public_key_768_from_external(public_key);
+  mlkem_encap_external_entropy(out_ciphertext, out_shared_secret, pub, entropy);
+  return bcm_infallible::approved;
+}
+
+bcm_infallible BCM_mlkem1024_encap_external_entropy(
+    uint8_t out_ciphertext[BCM_MLKEM1024_CIPHERTEXT_BYTES],
+    uint8_t out_shared_secret[BCM_MLKEM_SHARED_SECRET_BYTES],
+    const struct BCM_mlkem1024_public_key *public_key,
+    const uint8_t entropy[BCM_MLKEM_ENCAP_ENTROPY]) {
+  const struct mlkem::public_key<RANK1024> *pub =
+      mlkem::public_key_1024_from_external(public_key);
+  mlkem_encap_external_entropy(out_ciphertext, out_shared_secret, pub, entropy);
+  return bcm_infallible::approved;
+}
+
+bcm_status BCM_mlkem768_decap(
+    uint8_t out_shared_secret[BCM_MLKEM_SHARED_SECRET_BYTES],
+    const uint8_t *ciphertext, size_t ciphertext_len,
+    const struct BCM_mlkem768_private_key *private_key) {
+  if (ciphertext_len != BCM_MLKEM768_CIPHERTEXT_BYTES) {
+    RAND_bytes(out_shared_secret, BCM_MLKEM_SHARED_SECRET_BYTES);
+    return bcm_status::failure;
+  }
+  const struct mlkem::private_key<RANK768> *priv =
+      mlkem::private_key_768_from_external(private_key);
+  mlkem_decap(out_shared_secret, ciphertext, priv);
+  return bcm_status::approved;
+}
+
+bcm_status BCM_mlkem1024_decap(
+    uint8_t out_shared_secret[BCM_MLKEM_SHARED_SECRET_BYTES],
+    const uint8_t *ciphertext, size_t ciphertext_len,
+    const struct BCM_mlkem1024_private_key *private_key) {
+  if (ciphertext_len != BCM_MLKEM1024_CIPHERTEXT_BYTES) {
+    RAND_bytes(out_shared_secret, BCM_MLKEM_SHARED_SECRET_BYTES);
+    return bcm_status::failure;
+  }
+  const struct mlkem::private_key<RANK1024> *priv =
+      mlkem::private_key_1024_from_external(private_key);
+  mlkem_decap(out_shared_secret, ciphertext, priv);
+  return bcm_status::approved;
+}
+
+bcm_status BCM_mlkem768_marshal_public_key(
+    CBB *out, const struct BCM_mlkem768_public_key *public_key) {
+  return mlkem_marshal_public_key(
+      out, mlkem::public_key_768_from_external(public_key));
+}
+
+bcm_status BCM_mlkem1024_marshal_public_key(
+    CBB *out, const struct BCM_mlkem1024_public_key *public_key) {
+  return mlkem_marshal_public_key(
+      out, mlkem::public_key_1024_from_external(public_key));
+}
+
+bcm_status BCM_mlkem768_parse_public_key(
+    struct BCM_mlkem768_public_key *public_key, CBS *in) {
+  struct mlkem::public_key<RANK768> *pub =
+      mlkem::public_key_768_from_external(public_key);
+  if (!mlkem_parse_public_key(pub, in)) {
+    return bcm_status::failure;
+  }
+  return bcm_status::approved;
+}
+
+bcm_status BCM_mlkem1024_parse_public_key(
+    struct BCM_mlkem1024_public_key *public_key, CBS *in) {
+  struct mlkem::public_key<RANK1024> *pub =
+      mlkem::public_key_1024_from_external(public_key);
+  if (!mlkem_parse_public_key(pub, in)) {
+    return bcm_status::failure;
+  }
+  return bcm_status::approved;
+}
+
+bcm_status BCM_mlkem768_marshal_private_key(
+    CBB *out, const struct BCM_mlkem768_private_key *private_key) {
+  const struct mlkem::private_key<RANK768> *const priv =
+      mlkem::private_key_768_from_external(private_key);
+  if (!mlkem_marshal_private_key(out, priv)) {
+    return bcm_status::failure;
+  }
+  return bcm_status::approved;
+}
+
+bcm_status BCM_mlkem1024_marshal_private_key(
+    CBB *out, const struct BCM_mlkem1024_private_key *private_key) {
+  const struct mlkem::private_key<RANK1024> *const priv =
+      mlkem::private_key_1024_from_external(private_key);
+  if (!mlkem_marshal_private_key(out, priv)) {
+    return bcm_status::failure;
+  }
+  return bcm_status::approved;
+}
+
+bcm_status BCM_mlkem768_parse_private_key(
+    struct BCM_mlkem768_private_key *out_private_key, CBS *in) {
+  struct mlkem::private_key<RANK768> *const priv =
+      mlkem::private_key_768_from_external(out_private_key);
+  if (!mlkem_parse_private_key(priv, in)) {
+    return bcm_status::failure;
+  }
+  return bcm_status::approved;
+}
+
+bcm_status BCM_mlkem1024_parse_private_key(
+    struct BCM_mlkem1024_private_key *out_private_key, CBS *in) {
+  struct mlkem::private_key<RANK1024> *const priv =
+      mlkem::private_key_1024_from_external(out_private_key);
+  if (!mlkem_parse_private_key(priv, in)) {
+    return bcm_status::failure;
+  }
+  return bcm_status::approved;
+}
diff --git a/crypto/mlkem/internal.h b/crypto/mlkem/internal.h
deleted file mode 100644
index 8ab736d..0000000
--- a/crypto/mlkem/internal.h
+++ /dev/null
@@ -1,90 +0,0 @@
-/* Copyright 2023 The BoringSSL Authors
- *
- * Permission to use, copy, modify, and/or distribute this software for any
- * purpose with or without fee is hereby granted, provided that the above
- * copyright notice and this permission notice appear in all copies.
- *
- * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
- * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
- * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
- * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
- * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
- * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
- * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
-
-#ifndef OPENSSL_HEADER_CRYPTO_MLKEM_INTERNAL_H
-#define OPENSSL_HEADER_CRYPTO_MLKEM_INTERNAL_H
-
-#include <openssl/base.h>
-#include <openssl/mlkem.h>
-
-#if defined(__cplusplus)
-extern "C" {
-#endif
-
-
-// MLKEM_ENCAP_ENTROPY is the number of bytes of uniformly random entropy
-// necessary to encapsulate a secret. The entropy will be leaked to the
-// decapsulating party.
-#define MLKEM_ENCAP_ENTROPY 32
-
-// MLKEM768_generate_key_external_seed is a deterministic function to create a
-// pair of ML-KEM-768 keys, using the supplied seed. The seed needs to be
-// uniformly random. This function is should only be used for tests, regular
-// callers should use the non-deterministic |MLKEM768_generate_key| directly.
-OPENSSL_EXPORT void MLKEM768_generate_key_external_seed(
-    uint8_t out_encoded_public_key[MLKEM768_PUBLIC_KEY_BYTES],
-    struct MLKEM768_private_key *out_private_key,
-    const uint8_t seed[MLKEM_SEED_BYTES]);
-
-// MLKEM768_encap_external_entropy behaves like |MLKEM768_encap|, but uses
-// |MLKEM_ENCAP_ENTROPY| bytes of |entropy| for randomization. The decapsulating
-// side will be able to recover |entropy| in full. This function should only be
-// used for tests, regular callers should use the non-deterministic
-// |MLKEM768_encap| directly.
-OPENSSL_EXPORT void MLKEM768_encap_external_entropy(
-    uint8_t out_ciphertext[MLKEM768_CIPHERTEXT_BYTES],
-    uint8_t out_shared_secret[MLKEM_SHARED_SECRET_BYTES],
-    const struct MLKEM768_public_key *public_key,
-    const uint8_t entropy[MLKEM_ENCAP_ENTROPY]);
-
-// MLKEM768_marshal_private_key serializes |private_key| to |out| in the
-// NIST format for ML-KEM-768 private keys. It returns one on success or
-// zero on allocation error. (Note that one can also save just the seed value
-// produced by |MLKEM768_generate_key|, which is significantly smaller.)
-OPENSSL_EXPORT int MLKEM768_marshal_private_key(
-    CBB *out, const struct MLKEM768_private_key *private_key);
-
-// MLKEM1024_generate_key_external_seed is a deterministic function to create a
-// pair of ML-KEM-1024 keys, using the supplied seed. The seed needs to be
-// uniformly random. This function is should only be used for tests, regular
-// callers should use the non-deterministic |MLKEM1024_generate_key| directly.
-OPENSSL_EXPORT void MLKEM1024_generate_key_external_seed(
-    uint8_t out_encoded_public_key[MLKEM1024_PUBLIC_KEY_BYTES],
-    struct MLKEM1024_private_key *out_private_key,
-    const uint8_t seed[MLKEM_SEED_BYTES]);
-
-// MLKEM1024_encap_external_entropy behaves like |MLKEM1024_encap|, but uses
-// |MLKEM_ENCAP_ENTROPY| bytes of |entropy| for randomization. The
-// decapsulating side will be able to recover |entropy| in full. This function
-// should only be used for tests, regular callers should use the
-// non-deterministic |MLKEM1024_encap| directly.
-OPENSSL_EXPORT void MLKEM1024_encap_external_entropy(
-    uint8_t out_ciphertext[MLKEM1024_CIPHERTEXT_BYTES],
-    uint8_t out_shared_secret[MLKEM_SHARED_SECRET_BYTES],
-    const struct MLKEM1024_public_key *public_key,
-    const uint8_t entropy[MLKEM_ENCAP_ENTROPY]);
-
-// MLKEM1024_marshal_private_key serializes |private_key| to |out| in the
-// NIST format for ML-KEM-1024 private keys. It returns one on success or
-// zero on allocation error. (Note that one can also save just the seed value
-// produced by |MLKEM1024_generate_key|, which is significantly smaller.)
-OPENSSL_EXPORT int MLKEM1024_marshal_private_key(
-    CBB *out, const struct MLKEM1024_private_key *private_key);
-
-
-#if defined(__cplusplus)
-}
-#endif
-
-#endif  // OPENSSL_HEADER_CRYPTO_MLKEM_INTERNAL_H
diff --git a/crypto/mlkem/mlkem.cc b/crypto/mlkem/mlkem.cc
index 1636eca..21102c2 100644
--- a/crypto/mlkem/mlkem.cc
+++ b/crypto/mlkem/mlkem.cc
@@ -14,1084 +14,153 @@
 
 #include <openssl/mlkem.h>
 
-#include <assert.h>
-#include <stdint.h>
-#include <stdlib.h>
-#include <string.h>
-
-#include <openssl/base.h>
-#include <openssl/bytestring.h>
-#include <openssl/mem.h>
-#include <openssl/rand.h>
-
-#include "../fipsmodule/keccak/internal.h"
-#include "../internal.h"
-#include "./internal.h"
+#include "../fipsmodule/bcm_interface.h"
 
 
-// See
-// https://csrc.nist.gov/pubs/fips/203/final
-
-static void prf(uint8_t *out, size_t out_len, const uint8_t in[33]) {
-  BORINGSSL_keccak(out, out_len, in, 33, boringssl_shake256);
-}
-
-// Section 4.1
-static void hash_h(uint8_t out[32], const uint8_t *in, size_t len) {
-  BORINGSSL_keccak(out, 32, in, len, boringssl_sha3_256);
-}
-
-static void hash_g(uint8_t out[64], const uint8_t *in, size_t len) {
-  BORINGSSL_keccak(out, 64, in, len, boringssl_sha3_512);
-}
-
-// This is called `J` in the spec.
-static void kdf(uint8_t out[MLKEM_SHARED_SECRET_BYTES],
-                const uint8_t failure_secret[32], const uint8_t *ciphertext,
-                size_t ciphertext_len) {
-  struct BORINGSSL_keccak_st st;
-  BORINGSSL_keccak_init(&st, boringssl_shake256);
-  BORINGSSL_keccak_absorb(&st, failure_secret, 32);
-  BORINGSSL_keccak_absorb(&st, ciphertext, ciphertext_len);
-  BORINGSSL_keccak_squeeze(&st, out, MLKEM_SHARED_SECRET_BYTES);
-}
-
-// Constants that are common across all sizes.
-#define DEGREE 256
-static const size_t kBarrettMultiplier = 5039;
-static const unsigned kBarrettShift = 24;
-static const uint16_t kPrime = 3329;
-static const int kLog2Prime = 12;
-static const uint16_t kHalfPrime = (/*kPrime=*/3329 - 1) / 2;
-// kInverseDegree is 128^-1 mod 3329; 128 because kPrime does not have a 512th
-// root of unity.
-static const uint16_t kInverseDegree = 3303;
-
-// Rank-specific constants.
-#define RANK768 3
-static const int kDU768 = 10;
-static const int kDV768 = 4;
-#define RANK1024 4
-static const int kDU1024 = 11;
-static const int kDV1024 = 5;
-
-static constexpr size_t encoded_vector_size(int rank) {
-  return (kLog2Prime * DEGREE / 8) * static_cast<size_t>(rank);
-}
-
-static constexpr size_t encoded_public_key_size(int rank) {
-  return encoded_vector_size(rank) + /*sizeof(rho)=*/32;
-}
-
-static_assert(encoded_public_key_size(RANK768) == MLKEM768_PUBLIC_KEY_BYTES,
+static_assert(sizeof(BCM_mlkem768_private_key) <= sizeof(MLKEM768_private_key),
               "");
-static_assert(encoded_public_key_size(RANK1024) == MLKEM1024_PUBLIC_KEY_BYTES,
+static_assert(alignof(BCM_mlkem768_private_key) <=
+                  alignof(MLKEM768_private_key),
+              "");
+static_assert(sizeof(BCM_mlkem768_public_key) <= sizeof(MLKEM768_public_key),
+              "");
+static_assert(alignof(BCM_mlkem768_public_key) <= alignof(MLKEM768_public_key),
+              "");
+static_assert(MLKEM768_PUBLIC_KEY_BYTES == BCM_MLKEM768_PUBLIC_KEY_BYTES, "");
+static_assert(MLKEM_SEED_BYTES == BCM_MLKEM_SEED_BYTES, "");
+static_assert(MLKEM768_CIPHERTEXT_BYTES == BCM_MLKEM768_CIPHERTEXT_BYTES, "");
+static_assert(MLKEM_SHARED_SECRET_BYTES == BCM_MLKEM_SHARED_SECRET_BYTES, "");
+static_assert(MLKEM768_PRIVATE_KEY_BYTES == BCM_MLKEM768_PRIVATE_KEY_BYTES, "");
+static_assert(MLKEM1024_PUBLIC_KEY_BYTES == BCM_MLKEM1024_PUBLIC_KEY_BYTES, "");
+static_assert(MLKEM1024_CIPHERTEXT_BYTES == BCM_MLKEM1024_CIPHERTEXT_BYTES, "");
+static_assert(MLKEM1024_PRIVATE_KEY_BYTES == BCM_MLKEM1024_PRIVATE_KEY_BYTES,
               "");
 
-static constexpr size_t compressed_vector_size(int rank) {
-  // `if constexpr` isn't available in C++17.
-  return (rank == RANK768 ? kDU768 : kDU1024) * static_cast<size_t>(rank) *
-         DEGREE / 8;
-}
-
-static constexpr size_t ciphertext_size(int rank) {
-  return compressed_vector_size(rank) +
-         (rank == RANK768 ? kDV768 : kDV1024) * DEGREE / 8;
-}
-
-static_assert(ciphertext_size(RANK768) == MLKEM768_CIPHERTEXT_BYTES, "");
-static_assert(ciphertext_size(RANK1024) == MLKEM1024_CIPHERTEXT_BYTES, "");
-
-typedef struct scalar {
-  // On every function entry and exit, 0 <= c < kPrime.
-  uint16_t c[DEGREE];
-} scalar;
-
-template <int RANK>
-struct vector {
-  scalar v[RANK];
-};
-
-template <int RANK>
-struct matrix {
-  scalar v[RANK][RANK];
-};
-
-// This bit of Python will be referenced in some of the following comments:
-//
-// p = 3329
-//
-// def bitreverse(i):
-//     ret = 0
-//     for n in range(7):
-//         bit = i & 1
-//         ret <<= 1
-//         ret |= bit
-//         i >>= 1
-//     return ret
-
-// kNTTRoots = [pow(17, bitreverse(i), p) for i in range(128)]
-static const uint16_t kNTTRoots[128] = {
-    1,    1729, 2580, 3289, 2642, 630,  1897, 848,  1062, 1919, 193,  797,
-    2786, 3260, 569,  1746, 296,  2447, 1339, 1476, 3046, 56,   2240, 1333,
-    1426, 2094, 535,  2882, 2393, 2879, 1974, 821,  289,  331,  3253, 1756,
-    1197, 2304, 2277, 2055, 650,  1977, 2513, 632,  2865, 33,   1320, 1915,
-    2319, 1435, 807,  452,  1438, 2868, 1534, 2402, 2647, 2617, 1481, 648,
-    2474, 3110, 1227, 910,  17,   2761, 583,  2649, 1637, 723,  2288, 1100,
-    1409, 2662, 3281, 233,  756,  2156, 3015, 3050, 1703, 1651, 2789, 1789,
-    1847, 952,  1461, 2687, 939,  2308, 2437, 2388, 733,  2337, 268,  641,
-    1584, 2298, 2037, 3220, 375,  2549, 2090, 1645, 1063, 319,  2773, 757,
-    2099, 561,  2466, 2594, 2804, 1092, 403,  1026, 1143, 2150, 2775, 886,
-    1722, 1212, 1874, 1029, 2110, 2935, 885,  2154,
-};
-
-// kInverseNTTRoots = [pow(17, -bitreverse(i), p) for i in range(128)]
-static const uint16_t kInverseNTTRoots[128] = {
-    1,    1600, 40,   749,  2481, 1432, 2699, 687,  1583, 2760, 69,   543,
-    2532, 3136, 1410, 2267, 2508, 1355, 450,  936,  447,  2794, 1235, 1903,
-    1996, 1089, 3273, 283,  1853, 1990, 882,  3033, 2419, 2102, 219,  855,
-    2681, 1848, 712,  682,  927,  1795, 461,  1891, 2877, 2522, 1894, 1010,
-    1414, 2009, 3296, 464,  2697, 816,  1352, 2679, 1274, 1052, 1025, 2132,
-    1573, 76,   2998, 3040, 1175, 2444, 394,  1219, 2300, 1455, 2117, 1607,
-    2443, 554,  1179, 2186, 2303, 2926, 2237, 525,  735,  863,  2768, 1230,
-    2572, 556,  3010, 2266, 1684, 1239, 780,  2954, 109,  1292, 1031, 1745,
-    2688, 3061, 992,  2596, 941,  892,  1021, 2390, 642,  1868, 2377, 1482,
-    1540, 540,  1678, 1626, 279,  314,  1173, 2573, 3096, 48,   667,  1920,
-    2229, 1041, 2606, 1692, 680,  2746, 568,  3312,
-};
-
-// kModRoots = [pow(17, 2*bitreverse(i) + 1, p) for i in range(128)]
-static const uint16_t kModRoots[128] = {
-    17,   3312, 2761, 568,  583,  2746, 2649, 680,  1637, 1692, 723,  2606,
-    2288, 1041, 1100, 2229, 1409, 1920, 2662, 667,  3281, 48,   233,  3096,
-    756,  2573, 2156, 1173, 3015, 314,  3050, 279,  1703, 1626, 1651, 1678,
-    2789, 540,  1789, 1540, 1847, 1482, 952,  2377, 1461, 1868, 2687, 642,
-    939,  2390, 2308, 1021, 2437, 892,  2388, 941,  733,  2596, 2337, 992,
-    268,  3061, 641,  2688, 1584, 1745, 2298, 1031, 2037, 1292, 3220, 109,
-    375,  2954, 2549, 780,  2090, 1239, 1645, 1684, 1063, 2266, 319,  3010,
-    2773, 556,  757,  2572, 2099, 1230, 561,  2768, 2466, 863,  2594, 735,
-    2804, 525,  1092, 2237, 403,  2926, 1026, 2303, 1143, 2186, 2150, 1179,
-    2775, 554,  886,  2443, 1722, 1607, 1212, 2117, 1874, 1455, 1029, 2300,
-    2110, 1219, 2935, 394,  885,  2444, 2154, 1175,
-};
-
-// reduce_once reduces 0 <= x < 2*kPrime, mod kPrime.
-static uint16_t reduce_once(uint16_t x) {
-  assert(x < 2 * kPrime);
-  const uint16_t subtracted = x - kPrime;
-  uint16_t mask = 0u - (subtracted >> 15);
-  // On Aarch64, omitting a |value_barrier_u16| results in a 2x speedup of
-  // ML-KEM overall and Clang still produces constant-time code using `csel`. On
-  // other platforms & compilers on godbolt that we care about, this code also
-  // produces constant-time output.
-  return (mask & x) | (~mask & subtracted);
-}
-
-// constant time reduce x mod kPrime using Barrett reduction. x must be less
-// than kPrime + 2×kPrime².
-static uint16_t reduce(uint32_t x) {
-  assert(x < kPrime + 2u * kPrime * kPrime);
-  uint64_t product = (uint64_t)x * kBarrettMultiplier;
-  uint32_t quotient = (uint32_t)(product >> kBarrettShift);
-  uint32_t remainder = x - quotient * kPrime;
-  return reduce_once(remainder);
-}
-
-static void scalar_zero(scalar *out) { OPENSSL_memset(out, 0, sizeof(*out)); }
-
-template <int RANK>
-static void vector_zero(vector<RANK> *out) {
-  OPENSSL_memset(out->v, 0, sizeof(scalar) * RANK);
-}
-
-// In place number theoretic transform of a given scalar.
-// Note that MLKEM's kPrime 3329 does not have a 512th root of unity, so this
-// transform leaves off the last iteration of the usual FFT code, with the 128
-// relevant roots of unity being stored in |kNTTRoots|. This means the output
-// should be seen as 128 elements in GF(3329^2), with the coefficients of the
-// elements being consecutive entries in |s->c|.
-static void scalar_ntt(scalar *s) {
-  int offset = DEGREE;
-  // `int` is used here because using `size_t` throughout caused a ~5% slowdown
-  // with Clang 14 on Aarch64.
-  for (int step = 1; step < DEGREE / 2; step <<= 1) {
-    offset >>= 1;
-    int k = 0;
-    for (int i = 0; i < step; i++) {
-      const uint32_t step_root = kNTTRoots[i + step];
-      for (int j = k; j < k + offset; j++) {
-        uint16_t odd = reduce(step_root * s->c[j + offset]);
-        uint16_t even = s->c[j];
-        s->c[j] = reduce_once(odd + even);
-        s->c[j + offset] = reduce_once(even - odd + kPrime);
-      }
-      k += 2 * offset;
-    }
-  }
-}
-
-template <int RANK>
-static void vector_ntt(vector<RANK> *a) {
-  for (int i = 0; i < RANK; i++) {
-    scalar_ntt(&a->v[i]);
-  }
-}
-
-// In place inverse number theoretic transform of a given scalar, with pairs of
-// entries of s->v being interpreted as elements of GF(3329^2). Just as with the
-// number theoretic transform, this leaves off the first step of the normal iFFT
-// to account for the fact that 3329 does not have a 512th root of unity, using
-// the precomputed 128 roots of unity stored in |kInverseNTTRoots|.
-static void scalar_inverse_ntt(scalar *s) {
-  int step = DEGREE / 2;
-  // `int` is used here because using `size_t` throughout caused a ~5% slowdown
-  // with Clang 14 on Aarch64.
-  for (int offset = 2; offset < DEGREE; offset <<= 1) {
-    step >>= 1;
-    int k = 0;
-    for (int i = 0; i < step; i++) {
-      uint32_t step_root = kInverseNTTRoots[i + step];
-      for (int j = k; j < k + offset; j++) {
-        uint16_t odd = s->c[j + offset];
-        uint16_t even = s->c[j];
-        s->c[j] = reduce_once(odd + even);
-        s->c[j + offset] = reduce(step_root * (even - odd + kPrime));
-      }
-      k += 2 * offset;
-    }
-  }
-  for (int i = 0; i < DEGREE; i++) {
-    s->c[i] = reduce(s->c[i] * kInverseDegree);
-  }
-}
-
-template <int RANK>
-static void vector_inverse_ntt(vector<RANK> *a) {
-  for (int i = 0; i < RANK; i++) {
-    scalar_inverse_ntt(&a->v[i]);
-  }
-}
-
-static void scalar_add(scalar *lhs, const scalar *rhs) {
-  for (int i = 0; i < DEGREE; i++) {
-    lhs->c[i] = reduce_once(lhs->c[i] + rhs->c[i]);
-  }
-}
-
-static void scalar_sub(scalar *lhs, const scalar *rhs) {
-  for (int i = 0; i < DEGREE; i++) {
-    lhs->c[i] = reduce_once(lhs->c[i] - rhs->c[i] + kPrime);
-  }
-}
-
-// Multiplying two scalars in the number theoretically transformed state. Since
-// 3329 does not have a 512th root of unity, this means we have to interpret
-// the 2*ith and (2*i+1)th entries of the scalar as elements of GF(3329)[X]/(X^2
-// - 17^(2*bitreverse(i)+1)) The value of 17^(2*bitreverse(i)+1) mod 3329 is
-// stored in the precomputed |kModRoots| table. Note that our Barrett transform
-// only allows us to multipy two reduced numbers together, so we need some
-// intermediate reduction steps, even if an uint64_t could hold 3 multiplied
-// numbers.
-static void scalar_mult(scalar *out, const scalar *lhs, const scalar *rhs) {
-  for (int i = 0; i < DEGREE / 2; i++) {
-    uint32_t real_real = (uint32_t)lhs->c[2 * i] * rhs->c[2 * i];
-    uint32_t img_img = (uint32_t)lhs->c[2 * i + 1] * rhs->c[2 * i + 1];
-    uint32_t real_img = (uint32_t)lhs->c[2 * i] * rhs->c[2 * i + 1];
-    uint32_t img_real = (uint32_t)lhs->c[2 * i + 1] * rhs->c[2 * i];
-    out->c[2 * i] =
-        reduce(real_real + (uint32_t)reduce(img_img) * kModRoots[i]);
-    out->c[2 * i + 1] = reduce(img_real + real_img);
-  }
-}
-
-template <int RANK>
-static void vector_add(vector<RANK> *lhs, const vector<RANK> *rhs) {
-  for (int i = 0; i < RANK; i++) {
-    scalar_add(&lhs->v[i], &rhs->v[i]);
-  }
-}
-
-template <int RANK>
-static void matrix_mult(vector<RANK> *out, const matrix<RANK> *m,
-                        const vector<RANK> *a) {
-  vector_zero(out);
-  for (int i = 0; i < RANK; i++) {
-    for (int j = 0; j < RANK; j++) {
-      scalar product;
-      scalar_mult(&product, &m->v[i][j], &a->v[j]);
-      scalar_add(&out->v[i], &product);
-    }
-  }
-}
-
-template <int RANK>
-static void matrix_mult_transpose(vector<RANK> *out, const matrix<RANK> *m,
-                                  const vector<RANK> *a) {
-  vector_zero(out);
-  for (int i = 0; i < RANK; i++) {
-    for (int j = 0; j < RANK; j++) {
-      scalar product;
-      scalar_mult(&product, &m->v[j][i], &a->v[j]);
-      scalar_add(&out->v[i], &product);
-    }
-  }
-}
-
-template <int RANK>
-static void scalar_inner_product(scalar *out, const vector<RANK> *lhs,
-                                 const vector<RANK> *rhs) {
-  scalar_zero(out);
-  for (int i = 0; i < RANK; i++) {
-    scalar product;
-    scalar_mult(&product, &lhs->v[i], &rhs->v[i]);
-    scalar_add(out, &product);
-  }
-}
-
-// Algorithm 6 from the spec. Rejection samples a Keccak stream to get
-// uniformly distributed elements. This is used for matrix expansion and only
-// operates on public inputs.
-static void scalar_from_keccak_vartime(scalar *out,
-                                       struct BORINGSSL_keccak_st *keccak_ctx) {
-  assert(keccak_ctx->squeeze_offset == 0);
-  assert(keccak_ctx->rate_bytes == 168);
-  static_assert(168 % 3 == 0, "block and coefficient boundaries do not align");
-
-  int done = 0;
-  while (done < DEGREE) {
-    uint8_t block[168];
-    BORINGSSL_keccak_squeeze(keccak_ctx, block, sizeof(block));
-    for (size_t i = 0; i < sizeof(block) && done < DEGREE; i += 3) {
-      uint16_t d1 = block[i] + 256 * (block[i + 1] % 16);
-      uint16_t d2 = block[i + 1] / 16 + 16 * block[i + 2];
-      if (d1 < kPrime) {
-        out->c[done++] = d1;
-      }
-      if (d2 < kPrime && done < DEGREE) {
-        out->c[done++] = d2;
-      }
-    }
-  }
-}
-
-// Algorithm 7 from the spec, with eta fixed to two and the PRF call
-// included. Creates binominally distributed elements by sampling 2*|eta| bits,
-// and setting the coefficient to the count of the first bits minus the count of
-// the second bits, resulting in a centered binomial distribution. Since eta is
-// two this gives -2/2 with a probability of 1/16, -1/1 with probability 1/4,
-// and 0 with probability 3/8.
-static void scalar_centered_binomial_distribution_eta_2_with_prf(
-    scalar *out, const uint8_t input[33]) {
-  uint8_t entropy[128];
-  static_assert(sizeof(entropy) == 2 * /*kEta=*/2 * DEGREE / 8, "");
-  prf(entropy, sizeof(entropy), input);
-
-  for (int i = 0; i < DEGREE; i += 2) {
-    uint8_t byte = entropy[i / 2];
-
-    uint16_t value = kPrime;
-    value += (byte & 1) + ((byte >> 1) & 1);
-    value -= ((byte >> 2) & 1) + ((byte >> 3) & 1);
-    out->c[i] = reduce_once(value);
-
-    byte >>= 4;
-    value = kPrime;
-    value += (byte & 1) + ((byte >> 1) & 1);
-    value -= ((byte >> 2) & 1) + ((byte >> 3) & 1);
-    out->c[i + 1] = reduce_once(value);
-  }
-}
-
-// Generates a secret vector by using
-// |scalar_centered_binomial_distribution_eta_2_with_prf|, using the given seed
-// appending and incrementing |counter| for entry of the vector.
-template <int RANK>
-static void vector_generate_secret_eta_2(vector<RANK> *out, uint8_t *counter,
-                                         const uint8_t seed[32]) {
-  uint8_t input[33];
-  OPENSSL_memcpy(input, seed, 32);
-  for (int i = 0; i < RANK; i++) {
-    input[32] = (*counter)++;
-    scalar_centered_binomial_distribution_eta_2_with_prf(&out->v[i], input);
-  }
-}
-
-// Expands the matrix of a seed for key generation and for encaps-CPA.
-template <int RANK>
-static void matrix_expand(matrix<RANK> *out, const uint8_t rho[32]) {
-  uint8_t input[34];
-  OPENSSL_memcpy(input, rho, 32);
-  for (int i = 0; i < RANK; i++) {
-    for (int j = 0; j < RANK; j++) {
-      input[32] = i;
-      input[33] = j;
-      struct BORINGSSL_keccak_st keccak_ctx;
-      BORINGSSL_keccak_init(&keccak_ctx, boringssl_shake128);
-      BORINGSSL_keccak_absorb(&keccak_ctx, input, sizeof(input));
-      scalar_from_keccak_vartime(&out->v[i][j], &keccak_ctx);
-    }
-  }
-}
-
-static const uint8_t kMasks[8] = {0x01, 0x03, 0x07, 0x0f,
-                                  0x1f, 0x3f, 0x7f, 0xff};
-
-static void scalar_encode(uint8_t *out, const scalar *s, int bits) {
-  assert(bits <= (int)sizeof(*s->c) * 8 && bits != 1);
-
-  uint8_t out_byte = 0;
-  int out_byte_bits = 0;
-
-  for (int i = 0; i < DEGREE; i++) {
-    uint16_t element = s->c[i];
-    int element_bits_done = 0;
-
-    while (element_bits_done < bits) {
-      int chunk_bits = bits - element_bits_done;
-      int out_bits_remaining = 8 - out_byte_bits;
-      if (chunk_bits >= out_bits_remaining) {
-        chunk_bits = out_bits_remaining;
-        out_byte |= (element & kMasks[chunk_bits - 1]) << out_byte_bits;
-        *out = out_byte;
-        out++;
-        out_byte_bits = 0;
-        out_byte = 0;
-      } else {
-        out_byte |= (element & kMasks[chunk_bits - 1]) << out_byte_bits;
-        out_byte_bits += chunk_bits;
-      }
-
-      element_bits_done += chunk_bits;
-      element >>= chunk_bits;
-    }
-  }
-
-  if (out_byte_bits > 0) {
-    *out = out_byte;
-  }
-}
-
-// scalar_encode_1 is |scalar_encode| specialised for |bits| == 1.
-static void scalar_encode_1(uint8_t out[32], const scalar *s) {
-  for (int i = 0; i < DEGREE; i += 8) {
-    uint8_t out_byte = 0;
-    for (int j = 0; j < 8; j++) {
-      out_byte |= (s->c[i + j] & 1) << j;
-    }
-    *out = out_byte;
-    out++;
-  }
-}
-
-// Encodes an entire vector into 32*|RANK|*|bits| bytes. Note that since 256
-// (DEGREE) is divisible by 8, the individual vector entries will always fill a
-// whole number of bytes, so we do not need to worry about bit packing here.
-template <int RANK>
-static void vector_encode(uint8_t *out, const vector<RANK> *a, int bits) {
-  for (int i = 0; i < RANK; i++) {
-    scalar_encode(out + i * bits * DEGREE / 8, &a->v[i], bits);
-  }
-}
-
-// scalar_decode parses |DEGREE * bits| bits from |in| into |DEGREE| values in
-// |out|. It returns one on success and zero if any parsed value is >=
-// |kPrime|.
-static int scalar_decode(scalar *out, const uint8_t *in, int bits) {
-  assert(bits <= (int)sizeof(*out->c) * 8 && bits != 1);
-
-  uint8_t in_byte = 0;
-  int in_byte_bits_left = 0;
-
-  for (int i = 0; i < DEGREE; i++) {
-    uint16_t element = 0;
-    int element_bits_done = 0;
-
-    while (element_bits_done < bits) {
-      if (in_byte_bits_left == 0) {
-        in_byte = *in;
-        in++;
-        in_byte_bits_left = 8;
-      }
-
-      int chunk_bits = bits - element_bits_done;
-      if (chunk_bits > in_byte_bits_left) {
-        chunk_bits = in_byte_bits_left;
-      }
-
-      element |= (in_byte & kMasks[chunk_bits - 1]) << element_bits_done;
-      in_byte_bits_left -= chunk_bits;
-      in_byte >>= chunk_bits;
-
-      element_bits_done += chunk_bits;
-    }
-
-    if (element >= kPrime) {
-      return 0;
-    }
-    out->c[i] = element;
-  }
-
-  return 1;
-}
-
-// scalar_decode_1 is |scalar_decode| specialised for |bits| == 1.
-static void scalar_decode_1(scalar *out, const uint8_t in[32]) {
-  for (int i = 0; i < DEGREE; i += 8) {
-    uint8_t in_byte = *in;
-    in++;
-    for (int j = 0; j < 8; j++) {
-      out->c[i + j] = in_byte & 1;
-      in_byte >>= 1;
-    }
-  }
-}
-
-// Decodes 32*|RANK|*|bits| bytes from |in| into |out|. It returns one on
-// success or zero if any parsed value is >= |kPrime|.
-template <int RANK>
-static int vector_decode(vector<RANK> *out, const uint8_t *in, int bits) {
-  for (int i = 0; i < RANK; i++) {
-    if (!scalar_decode(&out->v[i], in + i * bits * DEGREE / 8, bits)) {
-      return 0;
-    }
-  }
-  return 1;
-}
-
-// Compresses (lossily) an input |x| mod 3329 into |bits| many bits by grouping
-// numbers close to each other together. The formula used is
-// round(2^|bits|/kPrime*x) mod 2^|bits|.
-// Uses Barrett reduction to achieve constant time. Since we need both the
-// remainder (for rounding) and the quotient (as the result), we cannot use
-// |reduce| here, but need to do the Barrett reduction directly.
-static uint16_t compress(uint16_t x, int bits) {
-  uint32_t shifted = (uint32_t)x << bits;
-  uint64_t product = (uint64_t)shifted * kBarrettMultiplier;
-  uint32_t quotient = (uint32_t)(product >> kBarrettShift);
-  uint32_t remainder = shifted - quotient * kPrime;
-
-  // Adjust the quotient to round correctly:
-  //   0 <= remainder <= kHalfPrime round to 0
-  //   kHalfPrime < remainder <= kPrime + kHalfPrime round to 1
-  //   kPrime + kHalfPrime < remainder < 2 * kPrime round to 2
-  assert(remainder < 2u * kPrime);
-  quotient += 1 & constant_time_lt_w(kHalfPrime, remainder);
-  quotient += 1 & constant_time_lt_w(kPrime + kHalfPrime, remainder);
-  return quotient & ((1 << bits) - 1);
-}
-
-// Decompresses |x| by using an equi-distant representative. The formula is
-// round(kPrime/2^|bits|*x). Note that 2^|bits| being the divisor allows us to
-// implement this logic using only bit operations.
-static uint16_t decompress(uint16_t x, int bits) {
-  uint32_t product = (uint32_t)x * kPrime;
-  uint32_t power = 1 << bits;
-  // This is |product| % power, since |power| is a power of 2.
-  uint32_t remainder = product & (power - 1);
-  // This is |product| / power, since |power| is a power of 2.
-  uint32_t lower = product >> bits;
-  // The rounding logic works since the first half of numbers mod |power| have a
-  // 0 as first bit, and the second half has a 1 as first bit, since |power| is
-  // a power of 2. As a 12 bit number, |remainder| is always positive, so we
-  // will shift in 0s for a right shift.
-  return lower + (remainder >> (bits - 1));
-}
-
-static void scalar_compress(scalar *s, int bits) {
-  for (int i = 0; i < DEGREE; i++) {
-    s->c[i] = compress(s->c[i], bits);
-  }
-}
-
-static void scalar_decompress(scalar *s, int bits) {
-  for (int i = 0; i < DEGREE; i++) {
-    s->c[i] = decompress(s->c[i], bits);
-  }
-}
-
-template <int RANK>
-static void vector_compress(vector<RANK> *a, int bits) {
-  for (int i = 0; i < RANK; i++) {
-    scalar_compress(&a->v[i], bits);
-  }
-}
-
-template <int RANK>
-static void vector_decompress(vector<RANK> *a, int bits) {
-  for (int i = 0; i < RANK; i++) {
-    scalar_decompress(&a->v[i], bits);
-  }
-}
-
-template <int RANK>
-struct public_key {
-  vector<RANK> t;
-  uint8_t rho[32];
-  uint8_t public_key_hash[32];
-  matrix<RANK> m;
-};
-
-static struct public_key<RANK768> *public_key_768_from_external(
-    const struct MLKEM768_public_key *external) {
-  static_assert(sizeof(struct MLKEM768_public_key) >=
-                    sizeof(struct public_key<RANK768>),
-                "MLKEM public key is too small");
-  static_assert(alignof(struct MLKEM768_public_key) >=
-                    alignof(struct public_key<RANK768>),
-                "MLKEM public key alignment incorrect");
-  return (struct public_key<RANK768> *)external;
-}
-
-static struct public_key<RANK1024> *
-public_key_1024_from_external(const struct MLKEM1024_public_key *external) {
-  static_assert(sizeof(struct MLKEM1024_public_key) >=
-                    sizeof(struct public_key<RANK1024>),
-                "MLKEM1024 public key is too small");
-  static_assert(alignof(struct MLKEM1024_public_key) >=
-                    alignof(struct public_key<RANK1024>),
-                "MLKEM1024 public key alignment incorrect");
-  return (struct public_key<RANK1024> *)external;
-}
-
-template <int RANK>
-struct private_key {
-  struct public_key<RANK> pub;
-  vector<RANK> s;
-  uint8_t fo_failure_secret[32];
-};
-
-static struct private_key<RANK768> *private_key_768_from_external(
-    const struct MLKEM768_private_key *external) {
-  static_assert(sizeof(struct MLKEM768_private_key) >=
-                    sizeof(struct private_key<RANK768>),
-                "MLKEM private key too small");
-  static_assert(alignof(struct MLKEM768_private_key) >=
-                    alignof(struct private_key<RANK768>),
-                "MLKEM private key alignment incorrect");
-  return (struct private_key<RANK768> *)external;
-}
-
-static struct private_key<RANK1024> *
-private_key_1024_from_external(const struct MLKEM1024_private_key *external) {
-  static_assert(sizeof(struct MLKEM1024_private_key) >=
-                    sizeof(struct private_key<RANK1024>),
-                "MLKEM1024 private key too small");
-  static_assert(alignof(struct MLKEM1024_private_key) >=
-                    alignof(struct private_key<RANK1024>),
-                "MLKEM1024 private key alignment incorrect");
-  return (struct private_key<RANK1024> *)external;
-}
-
-void MLKEM768_generate_key(uint8_t out_encoded_public_key[MLKEM768_PUBLIC_KEY_BYTES],
-                           uint8_t optional_out_seed[MLKEM_SEED_BYTES],
-                           struct MLKEM768_private_key *out_private_key) {
-  uint8_t seed[MLKEM_SEED_BYTES];
-  RAND_bytes(seed, sizeof(seed));
-  if (optional_out_seed) {
-    OPENSSL_memcpy(optional_out_seed, seed, sizeof(seed));
-  }
-  MLKEM768_generate_key_external_seed(out_encoded_public_key, out_private_key,
-                                      seed);
+void MLKEM768_generate_key(
+    uint8_t out_encoded_public_key[MLKEM768_PUBLIC_KEY_BYTES],
+    uint8_t optional_out_seed[MLKEM_SEED_BYTES],
+    struct MLKEM768_private_key *out_private_key) {
+  BCM_mlkem768_generate_key(
+      out_encoded_public_key, optional_out_seed,
+      reinterpret_cast<BCM_mlkem768_private_key *>(out_private_key));
 }
 
 int MLKEM768_private_key_from_seed(struct MLKEM768_private_key *out_private_key,
                                    const uint8_t *seed, size_t seed_len) {
-  if (seed_len != MLKEM_SEED_BYTES) {
-    return 0;
-  }
-  uint8_t public_key_bytes[MLKEM768_PUBLIC_KEY_BYTES];
-  MLKEM768_generate_key_external_seed(public_key_bytes, out_private_key, seed);
-  return 1;
-}
-
-void MLKEM1024_generate_key(
-    uint8_t out_encoded_public_key[MLKEM1024_PUBLIC_KEY_BYTES],
-    uint8_t optional_out_seed[MLKEM_SEED_BYTES],
-    struct MLKEM1024_private_key *out_private_key) {
-  uint8_t seed[MLKEM_SEED_BYTES];
-  RAND_bytes(seed, sizeof(seed));
-  if (optional_out_seed) {
-    OPENSSL_memcpy(optional_out_seed, seed, sizeof(seed));
-  }
-  MLKEM1024_generate_key_external_seed(out_encoded_public_key, out_private_key,
-                                       seed);
-}
-
-int MLKEM1024_private_key_from_seed(
-    struct MLKEM1024_private_key *out_private_key, const uint8_t *seed,
-    size_t seed_len) {
-  if (seed_len != MLKEM_SEED_BYTES) {
-    return 0;
-  }
-  uint8_t public_key_bytes[MLKEM1024_PUBLIC_KEY_BYTES];
-  MLKEM1024_generate_key_external_seed(public_key_bytes, out_private_key, seed);
-  return 1;
-}
-
-template <int RANK>
-static int mlkem_marshal_public_key(CBB *out,
-                                    const struct public_key<RANK> *pub) {
-  uint8_t *vector_output;
-  if (!CBB_add_space(out, &vector_output, encoded_vector_size(RANK))) {
-    return 0;
-  }
-  vector_encode(vector_output, &pub->t, kLog2Prime);
-  if (!CBB_add_bytes(out, pub->rho, sizeof(pub->rho))) {
-    return 0;
-  }
-  return 1;
-}
-
-template <int RANK>
-static void mlkem_generate_key_external_seed(
-    uint8_t *out_encoded_public_key, private_key<RANK> *priv,
-    const uint8_t seed[MLKEM_SEED_BYTES]) {
-  uint8_t augmented_seed[33];
-  OPENSSL_memcpy(augmented_seed, seed, 32);
-  augmented_seed[32] = RANK;
-
-  uint8_t hashed[64];
-  hash_g(hashed, augmented_seed, sizeof(augmented_seed));
-  const uint8_t *const rho = hashed;
-  const uint8_t *const sigma = hashed + 32;
-  OPENSSL_memcpy(priv->pub.rho, hashed, sizeof(priv->pub.rho));
-  matrix_expand(&priv->pub.m, rho);
-  uint8_t counter = 0;
-  vector_generate_secret_eta_2(&priv->s, &counter, sigma);
-  vector_ntt(&priv->s);
-  vector<RANK> error;
-  vector_generate_secret_eta_2(&error, &counter, sigma);
-  vector_ntt(&error);
-  matrix_mult_transpose(&priv->pub.t, &priv->pub.m, &priv->s);
-  vector_add(&priv->pub.t, &error);
-
-  CBB cbb;
-  CBB_init_fixed(&cbb, out_encoded_public_key, encoded_public_key_size(RANK));
-  if (!mlkem_marshal_public_key(&cbb, &priv->pub)) {
-    abort();
-  }
-
-  hash_h(priv->pub.public_key_hash, out_encoded_public_key,
-         encoded_public_key_size(RANK));
-  OPENSSL_memcpy(priv->fo_failure_secret, seed + 32, 32);
-}
-
-void MLKEM768_generate_key_external_seed(
-    uint8_t out_encoded_public_key[MLKEM768_PUBLIC_KEY_BYTES],
-    struct MLKEM768_private_key *out_private_key,
-    const uint8_t seed[MLKEM_SEED_BYTES]) {
-  private_key<RANK768> *priv = private_key_768_from_external(out_private_key);
-  mlkem_generate_key_external_seed(out_encoded_public_key, priv, seed);
-}
-
-void MLKEM1024_generate_key_external_seed(
-    uint8_t out_encoded_public_key[MLKEM1024_PUBLIC_KEY_BYTES],
-    struct MLKEM1024_private_key *out_private_key,
-    const uint8_t seed[MLKEM_SEED_BYTES]) {
-  private_key<RANK1024> *priv = private_key_1024_from_external(out_private_key);
-  mlkem_generate_key_external_seed(out_encoded_public_key, priv, seed);
+  return bcm_success(BCM_mlkem768_private_key_from_seed(
+      reinterpret_cast<BCM_mlkem768_private_key *>(out_private_key), seed,
+      seed_len));
 }
 
 void MLKEM768_public_from_private(
     struct MLKEM768_public_key *out_public_key,
     const struct MLKEM768_private_key *private_key) {
-  struct public_key<RANK768> *const pub =
-      public_key_768_from_external(out_public_key);
-  const struct ::private_key<RANK768> *const priv =
-      private_key_768_from_external(private_key);
-  *pub = priv->pub;
+  (void)BCM_mlkem768_public_from_private(
+      reinterpret_cast<BCM_mlkem768_public_key *>(out_public_key),
+      reinterpret_cast<const BCM_mlkem768_private_key *>(private_key));
 }
 
-void MLKEM1024_public_from_private(
-    struct MLKEM1024_public_key *out_public_key,
-    const struct MLKEM1024_private_key *private_key) {
-  struct public_key<RANK1024> *const pub =
-      public_key_1024_from_external(out_public_key);
-  const struct ::private_key<RANK1024> *const priv =
-      private_key_1024_from_external(private_key);
-  *pub = priv->pub;
-}
-
-// Encrypts a message with given randomness to
-// the ciphertext in |out|. Without applying the Fujisaki-Okamoto transform this
-// would not result in a CCA secure scheme, since lattice schemes are vulnerable
-// to decryption failure oracles.
-template <int RANK>
-static void encrypt_cpa(uint8_t *out, const struct public_key<RANK> *pub,
-                        const uint8_t message[32],
-                        const uint8_t randomness[32]) {
-  constexpr int du = RANK == RANK768 ? kDU768 : kDU1024;
-  constexpr int dv = RANK == RANK768 ? kDV768 : kDV1024;
-
-  uint8_t counter = 0;
-  vector<RANK> secret;
-  vector_generate_secret_eta_2(&secret, &counter, randomness);
-  vector_ntt(&secret);
-  vector<RANK> error;
-  vector_generate_secret_eta_2(&error, &counter, randomness);
-  uint8_t input[33];
-  OPENSSL_memcpy(input, randomness, 32);
-  input[32] = counter;
-  scalar scalar_error;
-  scalar_centered_binomial_distribution_eta_2_with_prf(&scalar_error, input);
-  vector<RANK> u;
-  matrix_mult(&u, &pub->m, &secret);
-  vector_inverse_ntt(&u);
-  vector_add(&u, &error);
-  scalar v;
-  scalar_inner_product(&v, &pub->t, &secret);
-  scalar_inverse_ntt(&v);
-  scalar_add(&v, &scalar_error);
-  scalar expanded_message;
-  scalar_decode_1(&expanded_message, message);
-  scalar_decompress(&expanded_message, 1);
-  scalar_add(&v, &expanded_message);
-  vector_compress(&u, du);
-  vector_encode(out, &u, du);
-  scalar_compress(&v, dv);
-  scalar_encode(out + compressed_vector_size(RANK), &v, dv);
-}
-
-// Calls |MLKEM768_encap_external_entropy| with random bytes from |RAND_bytes|
 void MLKEM768_encap(uint8_t out_ciphertext[MLKEM768_CIPHERTEXT_BYTES],
                     uint8_t out_shared_secret[MLKEM_SHARED_SECRET_BYTES],
                     const struct MLKEM768_public_key *public_key) {
-  uint8_t entropy[MLKEM_ENCAP_ENTROPY];
-  RAND_bytes(entropy, MLKEM_ENCAP_ENTROPY);
-  MLKEM768_encap_external_entropy(out_ciphertext, out_shared_secret, public_key,
-                                  entropy);
-}
-
-void MLKEM1024_encap(uint8_t out_ciphertext[MLKEM1024_CIPHERTEXT_BYTES],
-                     uint8_t out_shared_secret[MLKEM_SHARED_SECRET_BYTES],
-                     const struct MLKEM1024_public_key *public_key) {
-  uint8_t entropy[MLKEM_ENCAP_ENTROPY];
-  RAND_bytes(entropy, MLKEM_ENCAP_ENTROPY);
-  MLKEM1024_encap_external_entropy(out_ciphertext, out_shared_secret,
-                                   public_key, entropy);
-}
-
-// See section 6.2.
-template <int RANK>
-static void mlkem_encap_external_entropy(
-    uint8_t *out_ciphertext,
-    uint8_t out_shared_secret[MLKEM_SHARED_SECRET_BYTES],
-    const struct public_key<RANK> *pub,
-    const uint8_t entropy[MLKEM_ENCAP_ENTROPY]) {
-  uint8_t input[64];
-  OPENSSL_memcpy(input, entropy, MLKEM_ENCAP_ENTROPY);
-  OPENSSL_memcpy(input + MLKEM_ENCAP_ENTROPY, pub->public_key_hash,
-                 sizeof(input) - MLKEM_ENCAP_ENTROPY);
-  uint8_t key_and_randomness[64];
-  hash_g(key_and_randomness, input, sizeof(input));
-  encrypt_cpa(out_ciphertext, pub, entropy, key_and_randomness + 32);
-  static_assert(MLKEM_SHARED_SECRET_BYTES == 32, "");
-  memcpy(out_shared_secret, key_and_randomness, 32);
-}
-
-void MLKEM768_encap_external_entropy(
-    uint8_t out_ciphertext[MLKEM768_CIPHERTEXT_BYTES],
-    uint8_t out_shared_secret[MLKEM_SHARED_SECRET_BYTES],
-    const struct MLKEM768_public_key *public_key,
-    const uint8_t entropy[MLKEM_ENCAP_ENTROPY]) {
-  const struct ::public_key<RANK768> *pub =
-      public_key_768_from_external(public_key);
-  mlkem_encap_external_entropy(out_ciphertext, out_shared_secret, pub, entropy);
-}
-
-void MLKEM1024_encap_external_entropy(
-    uint8_t out_ciphertext[MLKEM1024_CIPHERTEXT_BYTES],
-    uint8_t out_shared_secret[MLKEM_SHARED_SECRET_BYTES],
-    const struct MLKEM1024_public_key *public_key,
-    const uint8_t entropy[MLKEM_ENCAP_ENTROPY]) {
-  const struct ::public_key<RANK1024> *pub =
-      public_key_1024_from_external(public_key);
-  mlkem_encap_external_entropy(out_ciphertext, out_shared_secret, pub, entropy);
-}
-
-template <int RANK>
-static void decrypt_cpa(uint8_t out[32], const struct private_key<RANK> *priv,
-                        const uint8_t ciphertext[MLKEM768_CIPHERTEXT_BYTES]) {
-  constexpr int du = RANK == RANK768 ? kDU768 : kDU1024;
-  constexpr int dv = RANK == RANK768 ? kDV768 : kDV1024;
-
-  vector<RANK> u;
-  vector_decode(&u, ciphertext, du);
-  vector_decompress(&u, du);
-  vector_ntt(&u);
-  scalar v;
-  scalar_decode(&v, ciphertext + compressed_vector_size(RANK), dv);
-  scalar_decompress(&v, dv);
-  scalar mask;
-  scalar_inner_product(&mask, &priv->s, &u);
-  scalar_inverse_ntt(&mask);
-  scalar_sub(&v, &mask);
-  scalar_compress(&v, 1);
-  scalar_encode_1(out, &v);
-}
-
-// See section 6.3
-template <int RANK>
-static void mlkem_decap(uint8_t out_shared_secret[MLKEM_SHARED_SECRET_BYTES],
-                        const uint8_t *ciphertext,
-                        const struct private_key<RANK> *priv) {
-  uint8_t decrypted[64];
-  decrypt_cpa(decrypted, priv, ciphertext);
-  OPENSSL_memcpy(decrypted + 32, priv->pub.public_key_hash,
-                 sizeof(decrypted) - 32);
-  uint8_t key_and_randomness[64];
-  hash_g(key_and_randomness, decrypted, sizeof(decrypted));
-  constexpr size_t ciphertext_len = ciphertext_size(RANK);
-  uint8_t expected_ciphertext[MLKEM1024_CIPHERTEXT_BYTES];
-  static_assert(ciphertext_len <= sizeof(expected_ciphertext), "");
-  encrypt_cpa(expected_ciphertext, &priv->pub, decrypted,
-              key_and_randomness + 32);
-
-  uint8_t failure_key[32];
-  kdf(failure_key, priv->fo_failure_secret, ciphertext, ciphertext_len);
-
-  uint8_t mask = constant_time_eq_int_8(
-      CRYPTO_memcmp(ciphertext, expected_ciphertext, ciphertext_len), 0);
-  for (int i = 0; i < MLKEM_SHARED_SECRET_BYTES; i++) {
-    out_shared_secret[i] =
-        constant_time_select_8(mask, key_and_randomness[i], failure_key[i]);
-  }
+  (void)BCM_mlkem768_encap(
+      out_ciphertext, out_shared_secret,
+      reinterpret_cast<const BCM_mlkem768_public_key *>(public_key));
 }
 
 int MLKEM768_decap(uint8_t out_shared_secret[MLKEM_SHARED_SECRET_BYTES],
                    const uint8_t *ciphertext, size_t ciphertext_len,
                    const struct MLKEM768_private_key *private_key) {
-  if (ciphertext_len != MLKEM768_CIPHERTEXT_BYTES) {
-    RAND_bytes(out_shared_secret, MLKEM_SHARED_SECRET_BYTES);
-    return 0;
-  }
-  const struct ::private_key<RANK768> *priv =
-      private_key_768_from_external(private_key);
-  mlkem_decap(out_shared_secret, ciphertext, priv);
-  return 1;
+  return bcm_success(BCM_mlkem768_decap(
+      out_shared_secret, ciphertext, ciphertext_len,
+      reinterpret_cast<const BCM_mlkem768_private_key *>(private_key)));
+}
+
+int MLKEM768_marshal_public_key(CBB *out,
+                                const struct MLKEM768_public_key *public_key) {
+  return bcm_success(BCM_mlkem768_marshal_public_key(
+      out, reinterpret_cast<const BCM_mlkem768_public_key *>(public_key)));
+}
+
+int MLKEM768_parse_public_key(struct MLKEM768_public_key *out_public_key,
+                              CBS *in) {
+  return bcm_success(BCM_mlkem768_parse_public_key(
+      reinterpret_cast<BCM_mlkem768_public_key *>(out_public_key), in));
+}
+
+int MLKEM768_parse_private_key(struct MLKEM768_private_key *out_private_key,
+                               CBS *in) {
+  return bcm_success(BCM_mlkem768_parse_private_key(
+      reinterpret_cast<BCM_mlkem768_private_key *>(out_private_key), in));
+}
+
+static_assert(sizeof(BCM_mlkem1024_private_key) <=
+                  sizeof(MLKEM1024_private_key),
+              "");
+static_assert(alignof(BCM_mlkem1024_private_key) <=
+                  alignof(MLKEM1024_private_key),
+              "");
+static_assert(sizeof(BCM_mlkem1024_public_key) <= sizeof(MLKEM1024_public_key),
+              "");
+static_assert(alignof(BCM_mlkem1024_public_key) <=
+                  alignof(MLKEM1024_public_key),
+              "");
+
+void MLKEM1024_generate_key(
+    uint8_t out_encoded_public_key[MLKEM1024_PUBLIC_KEY_BYTES],
+    uint8_t optional_out_seed[MLKEM_SEED_BYTES],
+    struct MLKEM1024_private_key *out_private_key) {
+  (void)BCM_mlkem1024_generate_key(
+      out_encoded_public_key, optional_out_seed,
+      reinterpret_cast<BCM_mlkem1024_private_key *>(out_private_key));
+}
+
+int MLKEM1024_private_key_from_seed(
+    struct MLKEM1024_private_key *out_private_key, const uint8_t *seed,
+    size_t seed_len) {
+  return bcm_success(BCM_mlkem1024_private_key_from_seed(
+      reinterpret_cast<BCM_mlkem1024_private_key *>(out_private_key), seed,
+      seed_len));
+}
+
+void MLKEM1024_public_from_private(
+    struct MLKEM1024_public_key *out_public_key,
+    const struct MLKEM1024_private_key *private_key) {
+  (void)BCM_mlkem1024_public_from_private(
+      reinterpret_cast<BCM_mlkem1024_public_key *>(out_public_key),
+      reinterpret_cast<const BCM_mlkem1024_private_key *>(private_key));
+}
+
+void MLKEM1024_encap(uint8_t out_ciphertext[MLKEM1024_CIPHERTEXT_BYTES],
+                     uint8_t out_shared_secret[MLKEM_SHARED_SECRET_BYTES],
+                     const struct MLKEM1024_public_key *public_key) {
+  (void)BCM_mlkem1024_encap(
+      out_ciphertext, out_shared_secret,
+      reinterpret_cast<const BCM_mlkem1024_public_key *>(public_key));
 }
 
 int MLKEM1024_decap(uint8_t out_shared_secret[MLKEM_SHARED_SECRET_BYTES],
                     const uint8_t *ciphertext, size_t ciphertext_len,
                     const struct MLKEM1024_private_key *private_key) {
-  if (ciphertext_len != MLKEM1024_CIPHERTEXT_BYTES) {
-    RAND_bytes(out_shared_secret, MLKEM_SHARED_SECRET_BYTES);
-    return 0;
-  }
-  const struct ::private_key<RANK1024> *priv =
-      private_key_1024_from_external(private_key);
-  mlkem_decap(out_shared_secret, ciphertext, priv);
-  return 1;
-}
-
-int MLKEM768_marshal_public_key(CBB *out,
-                                const struct MLKEM768_public_key *public_key) {
-  return mlkem_marshal_public_key(out,
-                                  public_key_768_from_external(public_key));
+  return bcm_success(BCM_mlkem1024_decap(
+      out_shared_secret, ciphertext, ciphertext_len,
+      reinterpret_cast<const BCM_mlkem1024_private_key *>(private_key)));
 }
 
 int MLKEM1024_marshal_public_key(
     CBB *out, const struct MLKEM1024_public_key *public_key) {
-  return mlkem_marshal_public_key(out,
-                                  public_key_1024_from_external(public_key));
+  return bcm_success(BCM_mlkem1024_marshal_public_key(
+      out, reinterpret_cast<const BCM_mlkem1024_public_key *>(public_key)));
 }
 
-// mlkem_parse_public_key_no_hash parses |in| into |pub| but doesn't calculate
-// the value of |pub->public_key_hash|.
-template <int RANK>
-static int mlkem_parse_public_key_no_hash(struct public_key<RANK> *pub,
-                                          CBS *in) {
-  CBS t_bytes;
-  if (!CBS_get_bytes(in, &t_bytes, encoded_vector_size(RANK)) ||
-      !vector_decode(&pub->t, CBS_data(&t_bytes), kLog2Prime) ||
-      !CBS_copy_bytes(in, pub->rho, sizeof(pub->rho))) {
-    return 0;
-  }
-  matrix_expand(&pub->m, pub->rho);
-  return 1;
-}
-
-template <int RANK>
-static int mlkem_parse_public_key(struct public_key<RANK> *pub, CBS *in) {
-  CBS orig_in = *in;
-  if (!mlkem_parse_public_key_no_hash(pub, in) ||  //
-      CBS_len(in) != 0) {
-    return 0;
-  }
-  hash_h(pub->public_key_hash, CBS_data(&orig_in), CBS_len(&orig_in));
-  return 1;
-}
-
-int MLKEM768_parse_public_key(struct MLKEM768_public_key *public_key, CBS *in) {
-  struct ::public_key<RANK768> *pub = public_key_768_from_external(public_key);
-  return mlkem_parse_public_key(pub, in);
-}
-
-int MLKEM1024_parse_public_key(struct MLKEM1024_public_key *public_key,
+int MLKEM1024_parse_public_key(struct MLKEM1024_public_key *out_public_key,
                                CBS *in) {
-  struct ::public_key<RANK1024> *pub =
-      public_key_1024_from_external(public_key);
-  return mlkem_parse_public_key(pub, in);
-}
-
-template <int RANK>
-static int mlkem_marshal_private_key(CBB *out,
-                                     const struct private_key<RANK> *priv) {
-  uint8_t *s_output;
-  if (!CBB_add_space(out, &s_output, encoded_vector_size(RANK))) {
-    return 0;
-  }
-  vector_encode(s_output, &priv->s, kLog2Prime);
-  if (!mlkem_marshal_public_key(out, &priv->pub) ||
-      !CBB_add_bytes(out, priv->pub.public_key_hash,
-                     sizeof(priv->pub.public_key_hash)) ||
-      !CBB_add_bytes(out, priv->fo_failure_secret,
-                     sizeof(priv->fo_failure_secret))) {
-    return 0;
-  }
-  return 1;
-}
-
-int MLKEM768_marshal_private_key(
-    CBB *out, const struct MLKEM768_private_key *private_key) {
-  const struct ::private_key<RANK768> *const priv =
-      private_key_768_from_external(private_key);
-  return mlkem_marshal_private_key(out, priv);
-}
-
-int MLKEM1024_marshal_private_key(
-    CBB *out, const struct MLKEM1024_private_key *private_key) {
-  const struct ::private_key<RANK1024> *const priv =
-      private_key_1024_from_external(private_key);
-  return mlkem_marshal_private_key(out, priv);
-}
-
-template <int RANK>
-static int mlkem_parse_private_key(struct private_key<RANK> *priv, CBS *in) {
-  CBS s_bytes;
-  if (!CBS_get_bytes(in, &s_bytes, encoded_vector_size(RANK)) ||
-      !vector_decode(&priv->s, CBS_data(&s_bytes), kLog2Prime) ||
-      !mlkem_parse_public_key_no_hash(&priv->pub, in) ||
-      !CBS_copy_bytes(in, priv->pub.public_key_hash,
-                      sizeof(priv->pub.public_key_hash)) ||
-      !CBS_copy_bytes(in, priv->fo_failure_secret,
-                      sizeof(priv->fo_failure_secret)) ||
-      CBS_len(in) != 0) {
-    return 0;
-  }
-  return 1;
-}
-
-int MLKEM768_parse_private_key(struct MLKEM768_private_key *out_private_key,
-                               CBS *in) {
-  struct private_key<RANK768> *const priv =
-      private_key_768_from_external(out_private_key);
-  return mlkem_parse_private_key(priv, in);
+  return bcm_success(BCM_mlkem1024_parse_public_key(
+      reinterpret_cast<BCM_mlkem1024_public_key *>(out_public_key), in));
 }
 
 int MLKEM1024_parse_private_key(struct MLKEM1024_private_key *out_private_key,
                                 CBS *in) {
-  struct private_key<RANK1024> *const priv =
-      private_key_1024_from_external(out_private_key);
-  return mlkem_parse_private_key(priv, in);
+  return bcm_success(BCM_mlkem1024_parse_private_key(
+      reinterpret_cast<BCM_mlkem1024_private_key *>(out_private_key), in));
 }
diff --git a/crypto/mlkem/mlkem_test.cc b/crypto/mlkem/mlkem_test.cc
index 2516302..68bc5fa 100644
--- a/crypto/mlkem/mlkem_test.cc
+++ b/crypto/mlkem/mlkem_test.cc
@@ -24,10 +24,10 @@
 #include <openssl/mem.h>
 #include <openssl/mlkem.h>
 
+#include "../fipsmodule/bcm_interface.h"
 #include "../fipsmodule/keccak/internal.h"
 #include "../test/file_test.h"
 #include "../test/test_util.h"
-#include "./internal.h"
 
 
 namespace {
@@ -49,11 +49,65 @@
   return ret;
 }
 
+// These functions wrap the methods that are only in the BCM interface. They
+// take care of casting the key types from the public keys to the BCM types.
+// That saves casting noise in the template functions.
+
+int wrapper_768_marshal_private_key(
+    CBB *out, const struct MLKEM768_private_key *private_key) {
+  return bcm_success(BCM_mlkem768_marshal_private_key(
+      out, reinterpret_cast<const BCM_mlkem768_private_key *>(private_key)));
+}
+
+int wrapper_1024_marshal_private_key(
+    CBB *out, const struct MLKEM1024_private_key *private_key) {
+  return bcm_success(BCM_mlkem1024_marshal_private_key(
+      out, reinterpret_cast<const BCM_mlkem1024_private_key *>(private_key)));
+}
+
+void wrapper_768_generate_key_external_seed(
+    uint8_t out_encoded_public_key[MLKEM768_PUBLIC_KEY_BYTES],
+    struct MLKEM768_private_key *out_private_key,
+    const uint8_t seed[MLKEM_SEED_BYTES]) {
+  BCM_mlkem768_generate_key_external_seed(
+      out_encoded_public_key,
+      reinterpret_cast<BCM_mlkem768_private_key *>(out_private_key), seed);
+}
+
+void wrapper_1024_generate_key_external_seed(
+    uint8_t out_encoded_public_key[MLKEM1024_PUBLIC_KEY_BYTES],
+    struct MLKEM1024_private_key *out_private_key,
+    const uint8_t seed[MLKEM_SEED_BYTES]) {
+  BCM_mlkem1024_generate_key_external_seed(
+      out_encoded_public_key,
+      reinterpret_cast<BCM_mlkem1024_private_key *>(out_private_key), seed);
+}
+
+void wrapper_768_encap_external_entropy(
+    uint8_t out_ciphertext[MLKEM768_CIPHERTEXT_BYTES],
+    uint8_t out_shared_secret[MLKEM_SHARED_SECRET_BYTES],
+    const struct MLKEM768_public_key *public_key,
+    const uint8_t entropy[BCM_MLKEM_ENCAP_ENTROPY]) {
+  BCM_mlkem768_encap_external_entropy(
+      out_ciphertext, out_shared_secret,
+      reinterpret_cast<const BCM_mlkem768_public_key *>(public_key), entropy);
+}
+
+void wrapper_1024_encap_external_entropy(
+    uint8_t out_ciphertext[MLKEM1024_CIPHERTEXT_BYTES],
+    uint8_t out_shared_secret[MLKEM_SHARED_SECRET_BYTES],
+    const struct MLKEM1024_public_key *public_key,
+    const uint8_t entropy[BCM_MLKEM_ENCAP_ENTROPY]) {
+  BCM_mlkem1024_encap_external_entropy(
+      out_ciphertext, out_shared_secret,
+      reinterpret_cast<const BCM_mlkem1024_public_key *>(public_key), entropy);
+}
+
 template <typename PUBLIC_KEY, size_t PUBLIC_KEY_BYTES, typename PRIVATE_KEY,
           size_t PRIVATE_KEY_BYTES,
           void (*GENERATE)(uint8_t *, uint8_t *, PRIVATE_KEY *),
           int (*FROM_SEED)(PRIVATE_KEY *, const uint8_t *, size_t),
-          void PUBLIC_FROM_PRIVATE(PUBLIC_KEY *, const PRIVATE_KEY *),
+          void (*PUBLIC_FROM_PRIVATE)(PUBLIC_KEY *, const PRIVATE_KEY *),
           int (*PARSE_PUBLIC)(PUBLIC_KEY *, CBS *),
           int (*MARSHAL_PUBLIC)(CBB *, const PUBLIC_KEY *),
           int (*PARSE_PRIVATE)(PRIVATE_KEY *, CBS *),
@@ -139,7 +193,7 @@
             MLKEM768_generate_key, MLKEM768_private_key_from_seed,
             MLKEM768_public_from_private, MLKEM768_parse_public_key,
             MLKEM768_marshal_public_key, MLKEM768_parse_private_key,
-            MLKEM768_marshal_private_key, MLKEM768_CIPHERTEXT_BYTES,
+            wrapper_768_marshal_private_key, MLKEM768_CIPHERTEXT_BYTES,
             MLKEM768_encap, MLKEM768_decap>();
 }
 
@@ -149,7 +203,7 @@
             MLKEM1024_generate_key, MLKEM1024_private_key_from_seed,
             MLKEM1024_public_from_private, MLKEM1024_parse_public_key,
             MLKEM1024_marshal_public_key, MLKEM1024_parse_private_key,
-            MLKEM1024_marshal_private_key, MLKEM1024_CIPHERTEXT_BYTES,
+            wrapper_1024_marshal_private_key, MLKEM1024_CIPHERTEXT_BYTES,
             MLKEM1024_encap, MLKEM1024_decap>();
 }
 
@@ -178,16 +232,17 @@
   FileTestGTest(
       "crypto/mlkem/mlkem768_keygen_tests.txt",
       MLKEMKeyGenFileTest<MLKEM768_public_key, MLKEM768_PUBLIC_KEY_BYTES,
-                          MLKEM768_private_key, MLKEM768_marshal_private_key,
-                          MLKEM768_generate_key_external_seed>);
+                          MLKEM768_private_key, wrapper_768_marshal_private_key,
+                          wrapper_768_generate_key_external_seed>);
 }
 
 TEST(MLKEMTest, KeyGen1024TestVectors) {
   FileTestGTest(
       "crypto/mlkem/mlkem1024_keygen_tests.txt",
       MLKEMKeyGenFileTest<MLKEM1024_public_key, MLKEM1024_PUBLIC_KEY_BYTES,
-                          MLKEM1024_private_key, MLKEM1024_marshal_private_key,
-                          MLKEM1024_generate_key_external_seed>);
+                          MLKEM1024_private_key,
+                          wrapper_1024_marshal_private_key,
+                          wrapper_1024_generate_key_external_seed>);
 }
 
 template <typename PUBLIC_KEY, size_t PUBLIC_KEY_BYTES, typename PRIVATE_KEY,
@@ -219,9 +274,10 @@
 TEST(MLKEMTest, NISTKeyGen768TestVectors) {
   FileTestGTest(
       "crypto/mlkem/mlkem768_nist_keygen_tests.txt",
-      MLKEMNistKeyGenFileTest<
-          MLKEM768_public_key, MLKEM768_PUBLIC_KEY_BYTES, MLKEM768_private_key,
-          MLKEM768_marshal_private_key, MLKEM768_generate_key_external_seed>);
+      MLKEMNistKeyGenFileTest<MLKEM768_public_key, MLKEM768_PUBLIC_KEY_BYTES,
+                              MLKEM768_private_key,
+                              wrapper_768_marshal_private_key,
+                              wrapper_768_generate_key_external_seed>);
 }
 
 TEST(MLKEMTest, NISTKeyGen1024TestVectors) {
@@ -229,8 +285,8 @@
       "crypto/mlkem/mlkem1024_nist_keygen_tests.txt",
       MLKEMNistKeyGenFileTest<MLKEM1024_public_key, MLKEM1024_PUBLIC_KEY_BYTES,
                               MLKEM1024_private_key,
-                              MLKEM1024_marshal_private_key,
-                              MLKEM1024_generate_key_external_seed>);
+                              wrapper_1024_marshal_private_key,
+                              wrapper_1024_generate_key_external_seed>);
 }
 
 template <typename PUBLIC_KEY, size_t PUBLIC_KEY_BYTES,
@@ -269,7 +325,7 @@
       "crypto/mlkem/mlkem768_encap_tests.txt",
       MLKEMEncapFileTest<MLKEM768_public_key, MLKEM768_PUBLIC_KEY_BYTES,
                          MLKEM768_parse_public_key, MLKEM768_CIPHERTEXT_BYTES,
-                         MLKEM768_encap_external_entropy>);
+                         wrapper_768_encap_external_entropy>);
 }
 
 TEST(MLKEMTest, Encap1024TestVectors) {
@@ -277,7 +333,7 @@
       "crypto/mlkem/mlkem1024_encap_tests.txt",
       MLKEMEncapFileTest<MLKEM1024_public_key, MLKEM1024_PUBLIC_KEY_BYTES,
                          MLKEM1024_parse_public_key, MLKEM1024_CIPHERTEXT_BYTES,
-                         MLKEM1024_encap_external_entropy>);
+                         wrapper_1024_encap_external_entropy>);
 }
 
 template <typename PRIVATE_KEY, size_t PRIVATE_KEY_BYTES,
@@ -391,7 +447,7 @@
     BORINGSSL_keccak_absorb(&results_st, encoded_priv.data(),
                             encoded_priv.size());
 
-    uint8_t encap_entropy[MLKEM_ENCAP_ENTROPY];
+    uint8_t encap_entropy[BCM_MLKEM_ENCAP_ENTROPY];
     BORINGSSL_keccak_squeeze(&generate_st, encap_entropy,
                              sizeof(encap_entropy));
     uint8_t ciphertext[CIPHERTEXT_BYTES];
@@ -421,9 +477,9 @@
   uint8_t result[32];
   IteratedTest<MLKEM768_public_key, MLKEM768_PUBLIC_KEY_BYTES,
                MLKEM768_private_key, MLKEM768_PRIVATE_KEY_BYTES,
-               MLKEM768_generate_key_external_seed,
-               MLKEM768_public_from_private, MLKEM768_marshal_private_key,
-               MLKEM768_CIPHERTEXT_BYTES, MLKEM768_encap_external_entropy,
+               wrapper_768_generate_key_external_seed,
+               MLKEM768_public_from_private, wrapper_768_marshal_private_key,
+               MLKEM768_CIPHERTEXT_BYTES, wrapper_768_encap_external_entropy,
                MLKEM768_decap>(result);
 
   const uint8_t kExpected[32] = {
@@ -442,9 +498,9 @@
   uint8_t result[32];
   IteratedTest<MLKEM1024_public_key, MLKEM1024_PUBLIC_KEY_BYTES,
                MLKEM1024_private_key, MLKEM1024_PRIVATE_KEY_BYTES,
-               MLKEM1024_generate_key_external_seed,
-               MLKEM1024_public_from_private, MLKEM1024_marshal_private_key,
-               MLKEM1024_CIPHERTEXT_BYTES, MLKEM1024_encap_external_entropy,
+               wrapper_1024_generate_key_external_seed,
+               MLKEM1024_public_from_private, wrapper_1024_marshal_private_key,
+               MLKEM1024_CIPHERTEXT_BYTES, wrapper_1024_encap_external_entropy,
                MLKEM1024_decap>(result);
 
   const uint8_t kExpected[32] = {
diff --git a/gen/sources.bzl b/gen/sources.bzl
index 15bf0b4..fe37da3 100644
--- a/gen/sources.bzl
+++ b/gen/sources.bzl
@@ -73,6 +73,7 @@
     "crypto/fipsmodule/hmac/hmac.cc.inc",
     "crypto/fipsmodule/keccak/keccak.cc.inc",
     "crypto/fipsmodule/mldsa/mldsa.cc.inc",
+    "crypto/fipsmodule/mlkem/mlkem.cc.inc",
     "crypto/fipsmodule/modes/cbc.cc.inc",
     "crypto/fipsmodule/modes/cfb.cc.inc",
     "crypto/fipsmodule/modes/ctr.cc.inc",
@@ -624,7 +625,6 @@
     "crypto/kyber/internal.h",
     "crypto/lhash/internal.h",
     "crypto/md5/internal.h",
-    "crypto/mlkem/internal.h",
     "crypto/obj/obj_dat.h",
     "crypto/pkcs7/internal.h",
     "crypto/pkcs8/internal.h",
diff --git a/gen/sources.cmake b/gen/sources.cmake
index b605a1c..9930094 100644
--- a/gen/sources.cmake
+++ b/gen/sources.cmake
@@ -77,6 +77,7 @@
   crypto/fipsmodule/hmac/hmac.cc.inc
   crypto/fipsmodule/keccak/keccak.cc.inc
   crypto/fipsmodule/mldsa/mldsa.cc.inc
+  crypto/fipsmodule/mlkem/mlkem.cc.inc
   crypto/fipsmodule/modes/cbc.cc.inc
   crypto/fipsmodule/modes/cfb.cc.inc
   crypto/fipsmodule/modes/ctr.cc.inc
@@ -642,7 +643,6 @@
   crypto/kyber/internal.h
   crypto/lhash/internal.h
   crypto/md5/internal.h
-  crypto/mlkem/internal.h
   crypto/obj/obj_dat.h
   crypto/pkcs7/internal.h
   crypto/pkcs8/internal.h
diff --git a/gen/sources.gni b/gen/sources.gni
index 17f2c74..7dcee0e 100644
--- a/gen/sources.gni
+++ b/gen/sources.gni
@@ -73,6 +73,7 @@
   "crypto/fipsmodule/hmac/hmac.cc.inc",
   "crypto/fipsmodule/keccak/keccak.cc.inc",
   "crypto/fipsmodule/mldsa/mldsa.cc.inc",
+  "crypto/fipsmodule/mlkem/mlkem.cc.inc",
   "crypto/fipsmodule/modes/cbc.cc.inc",
   "crypto/fipsmodule/modes/cfb.cc.inc",
   "crypto/fipsmodule/modes/ctr.cc.inc",
@@ -624,7 +625,6 @@
   "crypto/kyber/internal.h",
   "crypto/lhash/internal.h",
   "crypto/md5/internal.h",
-  "crypto/mlkem/internal.h",
   "crypto/obj/obj_dat.h",
   "crypto/pkcs7/internal.h",
   "crypto/pkcs8/internal.h",
diff --git a/gen/sources.json b/gen/sources.json
index d2afe74..5e978a8 100644
--- a/gen/sources.json
+++ b/gen/sources.json
@@ -58,6 +58,7 @@
       "crypto/fipsmodule/hmac/hmac.cc.inc",
       "crypto/fipsmodule/keccak/keccak.cc.inc",
       "crypto/fipsmodule/mldsa/mldsa.cc.inc",
+      "crypto/fipsmodule/mlkem/mlkem.cc.inc",
       "crypto/fipsmodule/modes/cbc.cc.inc",
       "crypto/fipsmodule/modes/cfb.cc.inc",
       "crypto/fipsmodule/modes/ctr.cc.inc",
@@ -606,7 +607,6 @@
       "crypto/kyber/internal.h",
       "crypto/lhash/internal.h",
       "crypto/md5/internal.h",
-      "crypto/mlkem/internal.h",
       "crypto/obj/obj_dat.h",
       "crypto/pkcs7/internal.h",
       "crypto/pkcs8/internal.h",