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/* Copyright (c) 2023, Google LLC
*
* 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. */
#define OPENSSL_UNSTABLE_EXPERIMENTAL_DILITHIUM
#include <openssl/experimental/dilithium.h>
#include <assert.h>
#include <stdlib.h>
#include <openssl/bytestring.h>
#include <openssl/rand.h>
#include "../internal.h"
#include "../keccak/internal.h"
#include "./internal.h"
#define DEGREE 256
#define K 6
#define L 5
#define ETA 4
#define TAU 49
#define BETA 196
#define OMEGA 55
#define RHO_BYTES 32
#define SIGMA_BYTES 64
#define K_BYTES 32
#define TR_BYTES 64
#define MU_BYTES 64
#define RHO_PRIME_BYTES 64
#define LAMBDA_BITS 192
#define LAMBDA_BYTES (LAMBDA_BITS / 8)
// 2^23 - 2^13 + 1
static const uint32_t kPrime = 8380417;
// Inverse of -kPrime modulo 2^32
static const uint32_t kPrimeNegInverse = 4236238847;
static const int kDroppedBits = 13;
static const uint32_t kHalfPrime = (8380417 - 1) / 2;
static const uint32_t kGamma1 = 1 << 19;
static const uint32_t kGamma2 = (8380417 - 1) / 32;
// 256^-1 mod kPrime, in Montgomery form.
static const uint32_t kInverseDegreeMontgomery = 41978;
typedef struct scalar {
uint32_t c[DEGREE];
} scalar;
typedef struct vectork {
scalar v[K];
} vectork;
typedef struct vectorl {
scalar v[L];
} vectorl;
typedef struct matrix {
scalar v[K][L];
} matrix;
/* Arithmetic */
// This bit of Python will be referenced in some of the following comments:
//
// q = 8380417
// # Inverse of -q modulo 2^32
// q_neg_inverse = 4236238847
// # 2^64 modulo q
// montgomery_square = 2365951
//
// def bitreverse(i):
// ret = 0
// for n in range(8):
// bit = i & 1
// ret <<= 1
// ret |= bit
// i >>= 1
// return ret
//
// def montgomery_reduce(x):
// a = (x * q_neg_inverse) % 2**32
// b = x + a * q
// assert b & 0xFFFF_FFFF == 0
// c = b >> 32
// assert c < q
// return c
//
// def montgomery_transform(x):
// return montgomery_reduce(x * montgomery_square)
// kNTTRootsMontgomery = [
// montgomery_transform(pow(1753, bitreverse(i), q)) for i in range(256)
// ]
static const uint32_t kNTTRootsMontgomery[256] = {
4193792, 25847, 5771523, 7861508, 237124, 7602457, 7504169, 466468,
1826347, 2353451, 8021166, 6288512, 3119733, 5495562, 3111497, 2680103,
2725464, 1024112, 7300517, 3585928, 7830929, 7260833, 2619752, 6271868,
6262231, 4520680, 6980856, 5102745, 1757237, 8360995, 4010497, 280005,
2706023, 95776, 3077325, 3530437, 6718724, 4788269, 5842901, 3915439,
4519302, 5336701, 3574422, 5512770, 3539968, 8079950, 2348700, 7841118,
6681150, 6736599, 3505694, 4558682, 3507263, 6239768, 6779997, 3699596,
811944, 531354, 954230, 3881043, 3900724, 5823537, 2071892, 5582638,
4450022, 6851714, 4702672, 5339162, 6927966, 3475950, 2176455, 6795196,
7122806, 1939314, 4296819, 7380215, 5190273, 5223087, 4747489, 126922,
3412210, 7396998, 2147896, 2715295, 5412772, 4686924, 7969390, 5903370,
7709315, 7151892, 8357436, 7072248, 7998430, 1349076, 1852771, 6949987,
5037034, 264944, 508951, 3097992, 44288, 7280319, 904516, 3958618,
4656075, 8371839, 1653064, 5130689, 2389356, 8169440, 759969, 7063561,
189548, 4827145, 3159746, 6529015, 5971092, 8202977, 1315589, 1341330,
1285669, 6795489, 7567685, 6940675, 5361315, 4499357, 4751448, 3839961,
2091667, 3407706, 2316500, 3817976, 5037939, 2244091, 5933984, 4817955,
266997, 2434439, 7144689, 3513181, 4860065, 4621053, 7183191, 5187039,
900702, 1859098, 909542, 819034, 495491, 6767243, 8337157, 7857917,
7725090, 5257975, 2031748, 3207046, 4823422, 7855319, 7611795, 4784579,
342297, 286988, 5942594, 4108315, 3437287, 5038140, 1735879, 203044,
2842341, 2691481, 5790267, 1265009, 4055324, 1247620, 2486353, 1595974,
4613401, 1250494, 2635921, 4832145, 5386378, 1869119, 1903435, 7329447,
7047359, 1237275, 5062207, 6950192, 7929317, 1312455, 3306115, 6417775,
7100756, 1917081, 5834105, 7005614, 1500165, 777191, 2235880, 3406031,
7838005, 5548557, 6709241, 6533464, 5796124, 4656147, 594136, 4603424,
6366809, 2432395, 2454455, 8215696, 1957272, 3369112, 185531, 7173032,
5196991, 162844, 1616392, 3014001, 810149, 1652634, 4686184, 6581310,
5341501, 3523897, 3866901, 269760, 2213111, 7404533, 1717735, 472078,
7953734, 1723600, 6577327, 1910376, 6712985, 7276084, 8119771, 4546524,
5441381, 6144432, 7959518, 6094090, 183443, 7403526, 1612842, 4834730,
7826001, 3919660, 8332111, 7018208, 3937738, 1400424, 7534263, 1976782};
// Reduces x mod kPrime in constant time, where 0 <= x < 2*kPrime.
static uint32_t reduce_once(uint32_t x) {
declassify_assert(x < 2 * kPrime);
// return x < kPrime ? x : x - kPrime;
return constant_time_select_int(constant_time_lt_w(x, kPrime), x, x - kPrime);
}
// Returns the absolute value in constant time.
static uint32_t abs_signed(uint32_t x) {
// return is_positive(x) ? x : -x;
// Note: MSVC doesn't like applying the unary minus operator to unsigned types
// (warning C4146), so we write the negation as a bitwise not plus one
// (assuming two's complement representation).
return constant_time_select_int(constant_time_lt_w(x, 0x80000000), x, ~x + 1);
}
// Returns the absolute value modulo kPrime.
static uint32_t abs_mod_prime(uint32_t x) {
declassify_assert(x < kPrime);
// return x > kHalfPrime ? kPrime - x : x;
return constant_time_select_int(constant_time_lt_w(kHalfPrime, x), kPrime - x,
x);
}
// Returns the maximum of two values in constant time.
static uint32_t maximum(uint32_t x, uint32_t y) {
// return x < y ? y : x;
return constant_time_select_int(constant_time_lt_w(x, y), y, x);
}
static void scalar_add(scalar *out, const scalar *lhs, const scalar *rhs) {
for (int i = 0; i < DEGREE; i++) {
out->c[i] = reduce_once(lhs->c[i] + rhs->c[i]);
}
}
static void scalar_sub(scalar *out, const scalar *lhs, const scalar *rhs) {
for (int i = 0; i < DEGREE; i++) {
out->c[i] = reduce_once(kPrime + lhs->c[i] - rhs->c[i]);
}
}
static uint32_t reduce_montgomery(uint64_t x) {
uint64_t a = (uint32_t)x * kPrimeNegInverse;
uint64_t b = x + a * kPrime;
declassify_assert((b & 0xffffffff) == 0);
uint32_t c = b >> 32;
return reduce_once(c);
}
// Multiply two scalars in the number theoretically transformed state.
static void scalar_mult(scalar *out, const scalar *lhs, const scalar *rhs) {
for (int i = 0; i < DEGREE; i++) {
out->c[i] = reduce_montgomery((uint64_t)lhs->c[i] * (uint64_t)rhs->c[i]);
}
}
// In place number theoretic transform of a given scalar.
//
// FIPS 204, Algorithm 35 (`NTT`).
static void scalar_ntt(scalar *s) {
// Step: 1, 2, 4, 8, ..., 128
// Offset: 128, 64, 32, 16, ..., 1
int offset = DEGREE;
for (int step = 1; step < DEGREE; step <<= 1) {
offset >>= 1;
int k = 0;
for (int i = 0; i < step; i++) {
assert(k == 2 * offset * i);
const uint32_t step_root = kNTTRootsMontgomery[step + i];
for (int j = k; j < k + offset; j++) {
uint32_t even = s->c[j];
uint32_t odd =
reduce_montgomery((uint64_t)step_root * (uint64_t)s->c[j + offset]);
s->c[j] = reduce_once(odd + even);
s->c[j + offset] = reduce_once(kPrime + even - odd);
}
k += 2 * offset;
}
}
}
// In place inverse number theoretic transform of a given scalar.
//
// FIPS 204, Algorithm 36 (`NTT^-1`).
static void scalar_inverse_ntt(scalar *s) {
// Step: 128, 64, 32, 16, ..., 1
// Offset: 1, 2, 4, 8, ..., 128
int step = DEGREE;
for (int offset = 1; offset < DEGREE; offset <<= 1) {
step >>= 1;
int k = 0;
for (int i = 0; i < step; i++) {
assert(k == 2 * offset * i);
const uint32_t step_root =
kPrime - kNTTRootsMontgomery[step + (step - 1 - i)];
for (int j = k; j < k + offset; j++) {
uint32_t even = s->c[j];
uint32_t odd = s->c[j + offset];
s->c[j] = reduce_once(odd + even);
s->c[j + offset] = reduce_montgomery((uint64_t)step_root *
(uint64_t)(kPrime + even - odd));
}
k += 2 * offset;
}
}
for (int i = 0; i < DEGREE; i++) {
s->c[i] = reduce_montgomery((uint64_t)s->c[i] *
(uint64_t)kInverseDegreeMontgomery);
}
}
static void vectork_zero(vectork *out) { OPENSSL_memset(out, 0, sizeof(*out)); }
static void vectork_add(vectork *out, const vectork *lhs, const vectork *rhs) {
for (int i = 0; i < K; i++) {
scalar_add(&out->v[i], &lhs->v[i], &rhs->v[i]);
}
}
static void vectork_sub(vectork *out, const vectork *lhs, const vectork *rhs) {
for (int i = 0; i < K; i++) {
scalar_sub(&out->v[i], &lhs->v[i], &rhs->v[i]);
}
}
static void vectork_mult_scalar(vectork *out, const vectork *lhs,
const scalar *rhs) {
for (int i = 0; i < K; i++) {
scalar_mult(&out->v[i], &lhs->v[i], rhs);
}
}
static void vectork_ntt(vectork *a) {
for (int i = 0; i < K; i++) {
scalar_ntt(&a->v[i]);
}
}
static void vectork_inverse_ntt(vectork *a) {
for (int i = 0; i < K; i++) {
scalar_inverse_ntt(&a->v[i]);
}
}
static void vectorl_add(vectorl *out, const vectorl *lhs, const vectorl *rhs) {
for (int i = 0; i < L; i++) {
scalar_add(&out->v[i], &lhs->v[i], &rhs->v[i]);
}
}
static void vectorl_mult_scalar(vectorl *out, const vectorl *lhs,
const scalar *rhs) {
for (int i = 0; i < L; i++) {
scalar_mult(&out->v[i], &lhs->v[i], rhs);
}
}
static void vectorl_ntt(vectorl *a) {
for (int i = 0; i < L; i++) {
scalar_ntt(&a->v[i]);
}
}
static void vectorl_inverse_ntt(vectorl *a) {
for (int i = 0; i < L; i++) {
scalar_inverse_ntt(&a->v[i]);
}
}
static void matrix_mult(vectork *out, const matrix *m, const vectorl *a) {
vectork_zero(out);
for (int i = 0; i < K; i++) {
for (int j = 0; j < L; j++) {
scalar product;
scalar_mult(&product, &m->v[i][j], &a->v[j]);
scalar_add(&out->v[i], &out->v[i], &product);
}
}
}
/* Rounding & hints */
// FIPS 204, Algorithm 29 (`Power2Round`).
static void power2_round(uint32_t *r1, uint32_t *r0, uint32_t r) {
*r1 = r >> kDroppedBits;
*r0 = r - (*r1 << kDroppedBits);
uint32_t r0_adjusted = reduce_once(kPrime + *r0 - (1 << kDroppedBits));
uint32_t r1_adjusted = *r1 + 1;
// Mask is set iff r0 > 2^(dropped_bits - 1).
crypto_word_t mask =
constant_time_lt_w((uint32_t)(1 << (kDroppedBits - 1)), *r0);
// r0 = mask ? r0_adjusted : r0
*r0 = constant_time_select_int(mask, r0_adjusted, *r0);
// r1 = mask ? r1_adjusted : r1
*r1 = constant_time_select_int(mask, r1_adjusted, *r1);
}
// Scale back previously rounded value.
static void scale_power2_round(uint32_t *out, uint32_t r1) {
// Pre-condition: 0 <= r1 <= 2^10 - 1
*out = r1 << kDroppedBits;
// Post-condition: 0 <= out <= 2^23 - 2^13 = kPrime - 1
assert(*out < kPrime);
}
// FIPS 204, Algorithm 31 (`HighBits`).
static uint32_t high_bits(uint32_t x) {
// Reference description (given 0 <= x < q):
//
// ```
// int32_t r0 = x mod+- (2 * kGamma2);
// if (x - r0 == q - 1) {
// return 0;
// } else {
// return (x - r0) / (2 * kGamma2);
// }
// ```
//
// Below is the formula taken from the reference implementation.
//
// Here, kGamma2 == 2^18 - 2^8
// This returns ((ceil(x / 2^7) * (2^10 + 1) + 2^21) / 2^22) mod 2^4
uint32_t r1 = (x + 127) >> 7;
r1 = (r1 * 1025 + (1 << 21)) >> 22;
r1 &= 15;
return r1;
}
// FIPS 204, Algorithm 30 (`Decompose`).
static void decompose(uint32_t *r1, int32_t *r0, uint32_t r) {
*r1 = high_bits(r);
*r0 = r;
*r0 -= *r1 * 2 * (int32_t)kGamma2;
*r0 -= (((int32_t)kHalfPrime - *r0) >> 31) & (int32_t)kPrime;
}
// FIPS 204, Algorithm 32 (`LowBits`).
static int32_t low_bits(uint32_t x) {
uint32_t r1;
int32_t r0;
decompose(&r1, &r0, x);
return r0;
}
// FIPS 204, Algorithm 33 (`MakeHint`).
static int32_t make_hint(uint32_t ct0, uint32_t cs2, uint32_t w) {
uint32_t r_plus_z = reduce_once(kPrime + w - cs2);
uint32_t r = reduce_once(r_plus_z + ct0);
return high_bits(r) != high_bits(r_plus_z);
}
// FIPS 204, Algorithm 34 (`UseHint`).
static uint32_t use_hint_vartime(uint32_t h, uint32_t r) {
uint32_t r1;
int32_t r0;
decompose(&r1, &r0, r);
if (h) {
if (r0 > 0) {
return (r1 + 1) & 15;
} else {
return (r1 - 1) & 15;
}
} else {
return r1;
}
}
static void scalar_power2_round(scalar *s1, scalar *s0, const scalar *s) {
for (int i = 0; i < DEGREE; i++) {
power2_round(&s1->c[i], &s0->c[i], s->c[i]);
}
}
static void scalar_scale_power2_round(scalar *out, const scalar *in) {
for (int i = 0; i < DEGREE; i++) {
scale_power2_round(&out->c[i], in->c[i]);
}
}
static void scalar_high_bits(scalar *out, const scalar *in) {
for (int i = 0; i < DEGREE; i++) {
out->c[i] = high_bits(in->c[i]);
}
}
static void scalar_low_bits(scalar *out, const scalar *in) {
for (int i = 0; i < DEGREE; i++) {
out->c[i] = low_bits(in->c[i]);
}
}
static void scalar_max(uint32_t *max, const scalar *s) {
for (int i = 0; i < DEGREE; i++) {
uint32_t abs = abs_mod_prime(s->c[i]);
*max = maximum(*max, abs);
}
}
static void scalar_max_signed(uint32_t *max, const scalar *s) {
for (int i = 0; i < DEGREE; i++) {
uint32_t abs = abs_signed(s->c[i]);
*max = maximum(*max, abs);
}
}
static void scalar_make_hint(scalar *out, const scalar *ct0, const scalar *cs2,
const scalar *w) {
for (int i = 0; i < DEGREE; i++) {
out->c[i] = make_hint(ct0->c[i], cs2->c[i], w->c[i]);
}
}
static void scalar_use_hint_vartime(scalar *out, const scalar *h,
const scalar *r) {
for (int i = 0; i < DEGREE; i++) {
out->c[i] = use_hint_vartime(h->c[i], r->c[i]);
}
}
static void vectork_power2_round(vectork *t1, vectork *t0, const vectork *t) {
for (int i = 0; i < K; i++) {
scalar_power2_round(&t1->v[i], &t0->v[i], &t->v[i]);
}
}
static void vectork_scale_power2_round(vectork *out, const vectork *in) {
for (int i = 0; i < K; i++) {
scalar_scale_power2_round(&out->v[i], &in->v[i]);
}
}
static void vectork_high_bits(vectork *out, const vectork *in) {
for (int i = 0; i < K; i++) {
scalar_high_bits(&out->v[i], &in->v[i]);
}
}
static void vectork_low_bits(vectork *out, const vectork *in) {
for (int i = 0; i < K; i++) {
scalar_low_bits(&out->v[i], &in->v[i]);
}
}
static uint32_t vectork_max(const vectork *a) {
uint32_t max = 0;
for (int i = 0; i < K; i++) {
scalar_max(&max, &a->v[i]);
}
return max;
}
static uint32_t vectork_max_signed(const vectork *a) {
uint32_t max = 0;
for (int i = 0; i < K; i++) {
scalar_max_signed(&max, &a->v[i]);
}
return max;
}
// The input vector contains only zeroes and ones.
static size_t vectork_count_ones(const vectork *a) {
size_t count = 0;
for (int i = 0; i < K; i++) {
for (int j = 0; j < DEGREE; j++) {
count += a->v[i].c[j];
}
}
return count;
}
static void vectork_make_hint(vectork *out, const vectork *ct0,
const vectork *cs2, const vectork *w) {
for (int i = 0; i < K; i++) {
scalar_make_hint(&out->v[i], &ct0->v[i], &cs2->v[i], &w->v[i]);
}
}
static void vectork_use_hint_vartime(vectork *out, const vectork *h,
const vectork *r) {
for (int i = 0; i < K; i++) {
scalar_use_hint_vartime(&out->v[i], &h->v[i], &r->v[i]);
}
}
static uint32_t vectorl_max(const vectorl *a) {
uint32_t max = 0;
for (int i = 0; i < L; i++) {
scalar_max(&max, &a->v[i]);
}
return max;
}
/* Bit packing */
static const uint8_t kMasks[8] = {0x01, 0x03, 0x07, 0x0f,
0x1f, 0x3f, 0x7f, 0xff};
// FIPS 204, Algorithm 10 (`SimpleBitPack`).
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++) {
uint32_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;
}
}
// FIPS 204, Algorithm 11 (`BitPack`).
static void scalar_encode_signed(uint8_t *out, const scalar *s, int bits,
uint32_t max) {
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++) {
uint32_t element = reduce_once(kPrime + max - s->c[i]);
declassify_assert(element <= 2 * max);
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;
}
}
// FIPS 204, Algorithm 12 (`SimpleBitUnpack`).
static void 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++) {
uint32_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;
}
out->c[i] = element;
}
}
// FIPS 204, Algorithm 13 (`BitUnpack`).
static int scalar_decode_signed(scalar *out, const uint8_t *in, int bits,
uint32_t max) {
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++) {
uint32_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;
}
// This may be only out of range in cases of invalid input, in which case it
// is okay to leak the value. This function is also called with secret
// input during signing, in |scalar_sample_mask|. However, in that case
// (and in any case when |max| is a power of two), this case is impossible.
if (constant_time_declassify_int(element > 2 * max)) {
return 0;
}
out->c[i] = reduce_once(kPrime + max - element);
}
return 1;
}
/* Expansion functions */
// FIPS 204, Algorithm 24 (`RejNTTPoly`).
//
// 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, const uint8_t derived_seed[RHO_BYTES + 2]) {
struct BORINGSSL_keccak_st keccak_ctx;
BORINGSSL_keccak_init(&keccak_ctx, boringssl_shake128);
BORINGSSL_keccak_absorb(&keccak_ctx, derived_seed, RHO_BYTES + 2);
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) {
// FIPS 204, Algorithm 8 (`CoeffFromThreeBytes`).
uint32_t value = (uint32_t)block[i] | ((uint32_t)block[i + 1] << 8) |
(((uint32_t)block[i + 2] & 0x7f) << 16);
if (value < kPrime) {
out->c[done++] = value;
}
}
}
}
// FIPS 204, Algorithm 25 (`RejBoundedPoly`).
static void scalar_uniform_eta_4(scalar *out,
const uint8_t derived_seed[SIGMA_BYTES + 2]) {
static_assert(ETA == 4, "This implementation is specialized for ETA == 4");
struct BORINGSSL_keccak_st keccak_ctx;
BORINGSSL_keccak_init(&keccak_ctx, boringssl_shake256);
BORINGSSL_keccak_absorb(&keccak_ctx, derived_seed, SIGMA_BYTES + 2);
assert(keccak_ctx.squeeze_offset == 0);
assert(keccak_ctx.rate_bytes == 136);
int done = 0;
while (done < DEGREE) {
uint8_t block[136];
BORINGSSL_keccak_squeeze(&keccak_ctx, block, sizeof(block));
for (size_t i = 0; i < sizeof(block) && done < DEGREE; ++i) {
uint32_t t0 = block[i] & 0x0F;
uint32_t t1 = block[i] >> 4;
// FIPS 204, Algorithm 9 (`CoefFromHalfByte`). Although both the input and
// output here are secret, it is OK to leak when we rejected a byte.
// Individual bytes of the SHAKE-256 stream are (indistiguishable from)
// independent of each other and the original seed, so leaking information
// about the rejected bytes does not reveal the input or output.
if (constant_time_declassify_int(t0 < 9)) {
out->c[done++] = reduce_once(kPrime + ETA - t0);
}
if (done < DEGREE && constant_time_declassify_int(t1 < 9)) {
out->c[done++] = reduce_once(kPrime + ETA - t1);
}
}
}
}
// FIPS 204, Algorithm 28 (`ExpandMask`).
static void scalar_sample_mask(
scalar *out, const uint8_t derived_seed[RHO_PRIME_BYTES + 2]) {
uint8_t buf[640];
BORINGSSL_keccak(buf, sizeof(buf), derived_seed, RHO_PRIME_BYTES + 2,
boringssl_shake256);
// Note: Decoding 20 bits into (-2^19, 2^19] cannot fail.
scalar_decode_signed(out, buf, 20, 1 << 19);
}
// FIPS 204, Algorithm 23 (`SampleInBall`).
static void scalar_sample_in_ball_vartime(scalar *out, const uint8_t *seed,
int len) {
assert(len == 32);
struct BORINGSSL_keccak_st keccak_ctx;
BORINGSSL_keccak_init(&keccak_ctx, boringssl_shake256);
BORINGSSL_keccak_absorb(&keccak_ctx, seed, len);
assert(keccak_ctx.squeeze_offset == 0);
assert(keccak_ctx.rate_bytes == 136);
uint8_t block[136];
BORINGSSL_keccak_squeeze(&keccak_ctx, block, sizeof(block));
uint64_t signs = CRYPTO_load_u64_le(block);
int offset = 8;
// SampleInBall implements a Fisher–Yates shuffle, which unavoidably leaks
// where the zeros are by memory access pattern. Although this leak happens
// before bad signatures are rejected, this is safe. See
// https://boringssl-review.googlesource.com/c/boringssl/+/67747/comment/8d8f01ac_70af3f21/
CONSTTIME_DECLASSIFY(block + offset, sizeof(block) - offset);
OPENSSL_memset(out, 0, sizeof(*out));
for (size_t i = DEGREE - TAU; i < DEGREE; i++) {
size_t byte;
for (;;) {
if (offset == 136) {
BORINGSSL_keccak_squeeze(&keccak_ctx, block, sizeof(block));
// See above.
CONSTTIME_DECLASSIFY(block, sizeof(block));
offset = 0;
}
byte = block[offset++];
if (byte <= i) {
break;
}
}
out->c[i] = out->c[byte];
out->c[byte] = reduce_once(kPrime + 1 - 2 * (signs & 1));
signs >>= 1;
}
}
// FIPS 204, Algorithm 26 (`ExpandA`).
static void matrix_expand(matrix *out, const uint8_t rho[RHO_BYTES]) {
static_assert(K <= 0x100, "K must fit in 8 bits");
static_assert(L <= 0x100, "L must fit in 8 bits");
uint8_t derived_seed[RHO_BYTES + 2];
OPENSSL_memcpy(derived_seed, rho, RHO_BYTES);
for (int i = 0; i < K; i++) {
for (int j = 0; j < L; j++) {
derived_seed[RHO_BYTES + 1] = i;
derived_seed[RHO_BYTES] = j;
scalar_from_keccak_vartime(&out->v[i][j], derived_seed);
}
}
}
// FIPS 204, Algorithm 27 (`ExpandS`).
static void vector_expand_short(vectorl *s1, vectork *s2,
const uint8_t sigma[SIGMA_BYTES]) {
static_assert(K <= 0x100, "K must fit in 8 bits");
static_assert(L <= 0x100, "L must fit in 8 bits");
static_assert(K + L <= 0x100, "K+L must fit in 8 bits");
uint8_t derived_seed[SIGMA_BYTES + 2];
OPENSSL_memcpy(derived_seed, sigma, SIGMA_BYTES);
derived_seed[SIGMA_BYTES] = 0;
derived_seed[SIGMA_BYTES + 1] = 0;
for (int i = 0; i < L; i++) {
scalar_uniform_eta_4(&s1->v[i], derived_seed);
++derived_seed[SIGMA_BYTES];
}
for (int i = 0; i < K; i++) {
scalar_uniform_eta_4(&s2->v[i], derived_seed);
++derived_seed[SIGMA_BYTES];
}
}
// FIPS 204, Algorithm 28 (`ExpandMask`).
static void vectorl_expand_mask(vectorl *out,
const uint8_t seed[RHO_PRIME_BYTES],
size_t kappa) {
assert(kappa + L <= 0x10000);
uint8_t derived_seed[RHO_PRIME_BYTES + 2];
OPENSSL_memcpy(derived_seed, seed, RHO_PRIME_BYTES);
for (int i = 0; i < L; i++) {
size_t index = kappa + i;
derived_seed[RHO_PRIME_BYTES] = index & 0xFF;
derived_seed[RHO_PRIME_BYTES + 1] = (index >> 8) & 0xFF;
scalar_sample_mask(&out->v[i], derived_seed);
}
}
/* Encoding */
// FIPS 204, Algorithm 10 (`SimpleBitPack`).
//
// Encodes an entire vector into 32*K*|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.
static void vectork_encode(uint8_t *out, const vectork *a, int bits) {
for (int i = 0; i < K; i++) {
scalar_encode(out + i * bits * DEGREE / 8, &a->v[i], bits);
}
}
// FIPS 204, Algorithm 12 (`SimpleBitUnpack`).
static void vectork_decode(vectork *out, const uint8_t *in, int bits) {
for (int i = 0; i < K; i++) {
scalar_decode(&out->v[i], in + i * bits * DEGREE / 8, bits);
}
}
static void vectork_encode_signed(uint8_t *out, const vectork *a, int bits,
uint32_t max) {
for (int i = 0; i < K; i++) {
scalar_encode_signed(out + i * bits * DEGREE / 8, &a->v[i], bits, max);
}
}
static int vectork_decode_signed(vectork *out, const uint8_t *in, int bits,
uint32_t max) {
for (int i = 0; i < K; i++) {
if (!scalar_decode_signed(&out->v[i], in + i * bits * DEGREE / 8, bits,
max)) {
return 0;
}
}
return 1;
}
// FIPS 204, Algorithm 11 (`BitPack`).
//
// Encodes an entire vector into 32*L*|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.
static void vectorl_encode_signed(uint8_t *out, const vectorl *a, int bits,
uint32_t max) {
for (int i = 0; i < L; i++) {
scalar_encode_signed(out + i * bits * DEGREE / 8, &a->v[i], bits, max);
}
}
static int vectorl_decode_signed(vectorl *out, const uint8_t *in, int bits,
uint32_t max) {
for (int i = 0; i < L; i++) {
if (!scalar_decode_signed(&out->v[i], in + i * bits * DEGREE / 8, bits,
max)) {
return 0;
}
}
return 1;
}
// FIPS 204, Algorithm 22 (`w1Encode`).
//
// The output must point to an array of 128*K bytes.
static void w1_encode(uint8_t *out, const vectork *w1) {
vectork_encode(out, w1, 4);
}
// FIPS 204, Algorithm 14 (`HintBitPack`).
static void hint_bit_pack(uint8_t *out, const vectork *h) {
OPENSSL_memset(out, 0, OMEGA + K);
int index = 0;
for (int i = 0; i < K; i++) {
for (int j = 0; j < DEGREE; j++) {
if (h->v[i].c[j]) {
out[index++] = j;
}
}
out[OMEGA + i] = index;
}
}
// FIPS 204, Algorithm 15 (`HintBitUnpack`).
static int hint_bit_unpack(vectork *h, const uint8_t *in) {
vectork_zero(h);
int index = 0;
for (int i = 0; i < K; i++) {
int limit = in[OMEGA + i];
if (limit < index || limit > OMEGA) {
return 0;
}
int last = -1;
while (index < limit) {
int byte = in[index++];
if (last >= 0 && byte <= last) {
return 0;
}
last = byte;
h->v[i].c[byte] = 1;
}
}
for (; index < OMEGA; index++) {
if (in[index] != 0) {
return 0;
}
}
return 1;
}
struct public_key {
uint8_t rho[RHO_BYTES];
vectork t1;
// Pre-cached value(s).
uint8_t public_key_hash[TR_BYTES];
};
struct private_key {
uint8_t rho[RHO_BYTES];
uint8_t k[K_BYTES];
uint8_t public_key_hash[TR_BYTES];
vectorl s1;
vectork s2;
vectork t0;
};
struct signature {
uint8_t c_tilde[2 * LAMBDA_BYTES];
vectorl z;
vectork h;
};
// FIPS 204, Algorithm 16 (`pkEncode`).
static int dilithium_marshal_public_key(CBB *out,
const struct public_key *pub) {
if (!CBB_add_bytes(out, pub->rho, sizeof(pub->rho))) {
return 0;
}
uint8_t *vectork_output;
if (!CBB_add_space(out, &vectork_output, 320 * K)) {
return 0;
}
vectork_encode(vectork_output, &pub->t1, 10);
return 1;
}
// FIPS 204, Algorithm 17 (`pkDecode`).
static int dilithium_parse_public_key(struct public_key *pub, CBS *in) {
if (!CBS_copy_bytes(in, pub->rho, sizeof(pub->rho))) {
return 0;
}
CBS t1_bytes;
if (!CBS_get_bytes(in, &t1_bytes, 320 * K)) {
return 0;
}
vectork_decode(&pub->t1, CBS_data(&t1_bytes), 10);
return 1;
}
// FIPS 204, Algorithm 18 (`skEncode`).
static int dilithium_marshal_private_key(CBB *out,
const struct private_key *priv) {
if (!CBB_add_bytes(out, priv->rho, sizeof(priv->rho)) ||
!CBB_add_bytes(out, priv->k, sizeof(priv->k)) ||
!CBB_add_bytes(out, priv->public_key_hash,
sizeof(priv->public_key_hash))) {
return 0;
}
uint8_t *vectorl_output;
if (!CBB_add_space(out, &vectorl_output, 128 * L)) {
return 0;
}
vectorl_encode_signed(vectorl_output, &priv->s1, 4, ETA);
uint8_t *vectork_output;
if (!CBB_add_space(out, &vectork_output, 128 * K)) {
return 0;
}
vectork_encode_signed(vectork_output, &priv->s2, 4, ETA);
if (!CBB_add_space(out, &vectork_output, 416 * K)) {
return 0;
}
vectork_encode_signed(vectork_output, &priv->t0, 13, 1 << 12);
return 1;
}
// FIPS 204, Algorithm 19 (`skDecode`).
static int dilithium_parse_private_key(struct private_key *priv, CBS *in) {
CBS s1_bytes;
CBS s2_bytes;
CBS t0_bytes;
if (!CBS_copy_bytes(in, priv->rho, sizeof(priv->rho)) ||
!CBS_copy_bytes(in, priv->k, sizeof(priv->k)) ||
!CBS_copy_bytes(in, priv->public_key_hash,
sizeof(priv->public_key_hash)) ||
!CBS_get_bytes(in, &s1_bytes, 128 * L) ||
!vectorl_decode_signed(&priv->s1, CBS_data(&s1_bytes), 4, ETA) ||
!CBS_get_bytes(in, &s2_bytes, 128 * K) ||
!vectork_decode_signed(&priv->s2, CBS_data(&s2_bytes), 4, ETA) ||
!CBS_get_bytes(in, &t0_bytes, 416 * K) ||
// Note: Decoding 13 bits into (-2^12, 2^12] cannot fail.
!vectork_decode_signed(&priv->t0, CBS_data(&t0_bytes), 13, 1 << 12)) {
return 0;
}
return 1;
}
// FIPS 204, Algorithm 20 (`sigEncode`).
static int dilithium_marshal_signature(CBB *out, const struct signature *sign) {
if (!CBB_add_bytes(out, sign->c_tilde, sizeof(sign->c_tilde))) {
return 0;
}
uint8_t *vectorl_output;
if (!CBB_add_space(out, &vectorl_output, 640 * L)) {
return 0;
}
vectorl_encode_signed(vectorl_output, &sign->z, 20, 1 << 19);
uint8_t *hint_output;
if (!CBB_add_space(out, &hint_output, OMEGA + K)) {
return 0;
}
hint_bit_pack(hint_output, &sign->h);
return 1;
}
// FIPS 204, Algorithm 21 (`sigDecode`).
static int dilithium_parse_signature(struct signature *sign, CBS *in) {
CBS z_bytes;
CBS hint_bytes;
if (!CBS_copy_bytes(in, sign->c_tilde, sizeof(sign->c_tilde)) ||
!CBS_get_bytes(in, &z_bytes, 640 * L) ||
// Note: Decoding 20 bits into (-2^19, 2^19] cannot fail.
!vectorl_decode_signed(&sign->z, CBS_data(&z_bytes), 20, 1 << 19) ||
!CBS_get_bytes(in, &hint_bytes, OMEGA + K) ||
!hint_bit_unpack(&sign->h, CBS_data(&hint_bytes))) {
return 0;
};
return 1;
}
static struct private_key *private_key_from_external(
const struct DILITHIUM_private_key *external) {
static_assert(
sizeof(struct DILITHIUM_private_key) == sizeof(struct private_key),
"Kyber private key size incorrect");
static_assert(
alignof(struct DILITHIUM_private_key) == alignof(struct private_key),
"Kyber private key align incorrect");
return (struct private_key *)external;
}
static struct public_key *public_key_from_external(
const struct DILITHIUM_public_key *external) {
static_assert(
sizeof(struct DILITHIUM_public_key) == sizeof(struct public_key),
"Dilithium public key size incorrect");
static_assert(
alignof(struct DILITHIUM_public_key) == alignof(struct public_key),
"Dilithium public key align incorrect");
return (struct public_key *)external;
}
/* API */
// Calls |DILITHIUM_generate_key_external_entropy| with random bytes from
// |RAND_bytes|. Returns 1 on success and 0 on failure.
int DILITHIUM_generate_key(
uint8_t out_encoded_public_key[DILITHIUM_PUBLIC_KEY_BYTES],
struct DILITHIUM_private_key *out_private_key) {
uint8_t entropy[DILITHIUM_GENERATE_KEY_ENTROPY];
RAND_bytes(entropy, sizeof(entropy));
return DILITHIUM_generate_key_external_entropy(out_encoded_public_key,
out_private_key, entropy);
}
// FIPS 204, Algorithm 1 (`ML-DSA.KeyGen`). Returns 1 on success and 0 on
// failure.
int DILITHIUM_generate_key_external_entropy(
uint8_t out_encoded_public_key[DILITHIUM_PUBLIC_KEY_BYTES],
struct DILITHIUM_private_key *out_private_key,
const uint8_t entropy[DILITHIUM_GENERATE_KEY_ENTROPY]) {
int ret = 0;
// Intermediate values, allocated on the heap to allow use when there is a
// limited amount of stack.
struct values_st {
struct public_key pub;
matrix a_ntt;
vectorl s1_ntt;
vectork t;
};
struct values_st *values = OPENSSL_malloc(sizeof(*values));
if (values == NULL) {
goto err;
}
struct private_key *priv = private_key_from_external(out_private_key);
uint8_t expanded_seed[RHO_BYTES + SIGMA_BYTES + K_BYTES];
BORINGSSL_keccak(expanded_seed, sizeof(expanded_seed), entropy,
DILITHIUM_GENERATE_KEY_ENTROPY, boringssl_shake256);
const uint8_t *const rho = expanded_seed;
const uint8_t *const sigma = expanded_seed + RHO_BYTES;
const uint8_t *const k = expanded_seed + RHO_BYTES + SIGMA_BYTES;
// rho is public.
CONSTTIME_DECLASSIFY(rho, RHO_BYTES);
OPENSSL_memcpy(values->pub.rho, rho, sizeof(values->pub.rho));
OPENSSL_memcpy(priv->rho, rho, sizeof(priv->rho));
OPENSSL_memcpy(priv->k, k, sizeof(priv->k));
matrix_expand(&values->a_ntt, rho);
vector_expand_short(&priv->s1, &priv->s2, sigma);
OPENSSL_memcpy(&values->s1_ntt, &priv->s1, sizeof(values->s1_ntt));
vectorl_ntt(&values->s1_ntt);
matrix_mult(&values->t, &values->a_ntt, &values->s1_ntt);
vectork_inverse_ntt(&values->t);
vectork_add(&values->t, &values->t, &priv->s2);
vectork_power2_round(&values->pub.t1, &priv->t0, &values->t);
// t1 is public.
CONSTTIME_DECLASSIFY(&values->pub.t1, sizeof(values->pub.t1));
CBB cbb;
CBB_init_fixed(&cbb, out_encoded_public_key, DILITHIUM_PUBLIC_KEY_BYTES);
if (!dilithium_marshal_public_key(&cbb, &values->pub)) {
goto err;
}
BORINGSSL_keccak(priv->public_key_hash, sizeof(priv->public_key_hash),
out_encoded_public_key, DILITHIUM_PUBLIC_KEY_BYTES,
boringssl_shake256);
ret = 1;
err:
OPENSSL_free(values);
return ret;
}
int DILITHIUM_public_from_private(
struct DILITHIUM_public_key *out_public_key,
const struct DILITHIUM_private_key *private_key) {
int ret = 0;
// Intermediate values, allocated on the heap to allow use when there is a
// limited amount of stack.
struct values_st {
matrix a_ntt;
vectorl s1_ntt;
vectork t;
vectork t0;
};
struct values_st *values = OPENSSL_malloc(sizeof(*values));
if (values == NULL) {
goto err;
}
const struct private_key *priv = private_key_from_external(private_key);
struct public_key *pub = public_key_from_external(out_public_key);
OPENSSL_memcpy(pub->rho, priv->rho, sizeof(pub->rho));
OPENSSL_memcpy(pub->public_key_hash, priv->public_key_hash,
sizeof(pub->public_key_hash));
matrix_expand(&values->a_ntt, priv->rho);
OPENSSL_memcpy(&values->s1_ntt, &priv->s1, sizeof(values->s1_ntt));
vectorl_ntt(&values->s1_ntt);
matrix_mult(&values->t, &values->a_ntt, &values->s1_ntt);
vectork_inverse_ntt(&values->t);
vectork_add(&values->t, &values->t, &priv->s2);
vectork_power2_round(&pub->t1, &values->t0, &values->t);
ret = 1;
err:
OPENSSL_free(values);
return ret;
}
// FIPS 204, Algorithm 2 (`ML-DSA.Sign`). Returns 1 on success and 0 on failure.
static int dilithium_sign_with_randomizer(
uint8_t out_encoded_signature[DILITHIUM_SIGNATURE_BYTES],
const struct DILITHIUM_private_key *private_key, const uint8_t *msg,
size_t msg_len,
const uint8_t randomizer[DILITHIUM_SIGNATURE_RANDOMIZER_BYTES]) {
int ret = 0;
const struct private_key *priv = private_key_from_external(private_key);
uint8_t mu[MU_BYTES];
struct BORINGSSL_keccak_st keccak_ctx;
BORINGSSL_keccak_init(&keccak_ctx, boringssl_shake256);
BORINGSSL_keccak_absorb(&keccak_ctx, priv->public_key_hash,
sizeof(priv->public_key_hash));
BORINGSSL_keccak_absorb(&keccak_ctx, msg, msg_len);
BORINGSSL_keccak_squeeze(&keccak_ctx, mu, MU_BYTES);
uint8_t rho_prime[RHO_PRIME_BYTES];
BORINGSSL_keccak_init(&keccak_ctx, boringssl_shake256);
BORINGSSL_keccak_absorb(&keccak_ctx, priv->k, sizeof(priv->k));
BORINGSSL_keccak_absorb(&keccak_ctx, randomizer,
DILITHIUM_SIGNATURE_RANDOMIZER_BYTES);
BORINGSSL_keccak_absorb(&keccak_ctx, mu, MU_BYTES);
BORINGSSL_keccak_squeeze(&keccak_ctx, rho_prime, RHO_PRIME_BYTES);
// Intermediate values, allocated on the heap to allow use when there is a
// limited amount of stack.
struct values_st {
struct signature sign;
vectorl s1_ntt;
vectork s2_ntt;
vectork t0_ntt;
matrix a_ntt;
vectorl y;
vectorl y_ntt;
vectork w;
vectork w1;
vectorl cs1;
vectork cs2;
vectork r0;
vectork ct0;
};
struct values_st *values = OPENSSL_malloc(sizeof(*values));
if (values == NULL) {
goto err;
}
OPENSSL_memcpy(&values->s1_ntt, &priv->s1, sizeof(values->s1_ntt));
vectorl_ntt(&values->s1_ntt);
OPENSSL_memcpy(&values->s2_ntt, &priv->s2, sizeof(values->s2_ntt));
vectork_ntt(&values->s2_ntt);
OPENSSL_memcpy(&values->t0_ntt, &priv->t0, sizeof(values->t0_ntt));
vectork_ntt(&values->t0_ntt);
matrix_expand(&values->a_ntt, priv->rho);
for (size_t kappa = 0;; kappa += L) {
// TODO(bbe): y only lives long enough to compute y_ntt.
// consider using another vectorl to save memory.
vectorl_expand_mask(&values->y, rho_prime, kappa);
OPENSSL_memcpy(&values->y_ntt, &values->y, sizeof(values->y_ntt));
vectorl_ntt(&values->y_ntt);
// TODO(bbe): w only lives long enough to compute y_ntt.
// consider using another vectork to save memory.
matrix_mult(&values->w, &values->a_ntt, &values->y_ntt);
vectork_inverse_ntt(&values->w);
vectork_high_bits(&values->w1, &values->w);
uint8_t w1_encoded[128 * K];
w1_encode(w1_encoded, &values->w1);
BORINGSSL_keccak_init(&keccak_ctx, boringssl_shake256);
BORINGSSL_keccak_absorb(&keccak_ctx, mu, MU_BYTES);
BORINGSSL_keccak_absorb(&keccak_ctx, w1_encoded, 128 * K);
BORINGSSL_keccak_squeeze(&keccak_ctx, values->sign.c_tilde,
2 * LAMBDA_BYTES);
scalar c_ntt;
scalar_sample_in_ball_vartime(&c_ntt, values->sign.c_tilde, 32);
scalar_ntt(&c_ntt);
vectorl_mult_scalar(&values->cs1, &values->s1_ntt, &c_ntt);
vectorl_inverse_ntt(&values->cs1);
vectork_mult_scalar(&values->cs2, &values->s2_ntt, &c_ntt);
vectork_inverse_ntt(&values->cs2);
vectorl_add(&values->sign.z, &values->y, &values->cs1);
vectork_sub(&values->r0, &values->w, &values->cs2);
vectork_low_bits(&values->r0, &values->r0);
// Leaking the fact that a signature was rejected is fine as the next
// attempt at a signature will be (indistinguishable from) independent of
// this one. Note, however, that we additionally leak which of the two
// branches rejected the signature. Section 5.5 of
// https://pq-crystals.org/dilithium/data/dilithium-specification-round3.pdf
// describes this leak as OK. Note we leak less than what is described by
// the paper; we do not reveal which coefficient violated the bound, and we
// hide which of the |z_max| or |r0_max| bound failed. See also
// https://boringssl-review.googlesource.com/c/boringssl/+/67747/comment/2bbab0fa_d241d35a/
uint32_t z_max = vectorl_max(&values->sign.z);
uint32_t r0_max = vectork_max_signed(&values->r0);
if (constant_time_declassify_w(
constant_time_ge_w(z_max, kGamma1 - BETA) |
constant_time_ge_w(r0_max, kGamma2 - BETA))) {
continue;
}
vectork_mult_scalar(&values->ct0, &values->t0_ntt, &c_ntt);
vectork_inverse_ntt(&values->ct0);
vectork_make_hint(&values->sign.h, &values->ct0, &values->cs2, &values->w);
// See above.
uint32_t ct0_max = vectork_max(&values->ct0);
size_t h_ones = vectork_count_ones(&values->sign.h);
if (constant_time_declassify_w(constant_time_ge_w(ct0_max, kGamma2) |
constant_time_lt_w(OMEGA, h_ones))) {
continue;
}
// Although computed with the private key, the signature is public.
CONSTTIME_DECLASSIFY(values->sign.c_tilde, sizeof(values->sign.c_tilde));
CONSTTIME_DECLASSIFY(&values->sign.z, sizeof(values->sign.z));
CONSTTIME_DECLASSIFY(&values->sign.h, sizeof(values->sign.h));
CBB cbb;
CBB_init_fixed(&cbb, out_encoded_signature, DILITHIUM_SIGNATURE_BYTES);
if (!dilithium_marshal_signature(&cbb, &values->sign)) {
goto err;
}
BSSL_CHECK(CBB_len(&cbb) == DILITHIUM_SIGNATURE_BYTES);
ret = 1;
break;
}
err:
OPENSSL_free(values);
return ret;
}
// Dilithium signature in deterministic mode. Returns 1 on success and 0 on
// failure.
int DILITHIUM_sign_deterministic(
uint8_t out_encoded_signature[DILITHIUM_SIGNATURE_BYTES],
const struct DILITHIUM_private_key *private_key, const uint8_t *msg,
size_t msg_len) {
uint8_t randomizer[DILITHIUM_SIGNATURE_RANDOMIZER_BYTES];
OPENSSL_memset(randomizer, 0, sizeof(randomizer));
return dilithium_sign_with_randomizer(out_encoded_signature, private_key, msg,
msg_len, randomizer);
}
// Dilithium signature in randomized mode, filling the random bytes with
// |RAND_bytes|. Returns 1 on success and 0 on failure.
int DILITHIUM_sign(uint8_t out_encoded_signature[DILITHIUM_SIGNATURE_BYTES],
const struct DILITHIUM_private_key *private_key,
const uint8_t *msg, size_t msg_len) {
uint8_t randomizer[DILITHIUM_SIGNATURE_RANDOMIZER_BYTES];
RAND_bytes(randomizer, sizeof(randomizer));
return dilithium_sign_with_randomizer(out_encoded_signature, private_key, msg,
msg_len, randomizer);
}
// FIPS 204, Algorithm 3 (`ML-DSA.Verify`).
int DILITHIUM_verify(const struct DILITHIUM_public_key *public_key,
const uint8_t encoded_signature[DILITHIUM_SIGNATURE_BYTES],
const uint8_t *msg, size_t msg_len) {
int ret = 0;
// Intermediate values, allocated on the heap to allow use when there is a
// limited amount of stack.
struct values_st {
struct signature sign;
matrix a_ntt;
vectorl z_ntt;
vectork az_ntt;
vectork t1_ntt;
vectork ct1_ntt;
vectork w_approx;
vectork w1;
};
struct values_st *values = OPENSSL_malloc(sizeof(*values));
if (values == NULL) {
goto err;
}
const struct public_key *pub = public_key_from_external(public_key);
CBS cbs;
CBS_init(&cbs, encoded_signature, DILITHIUM_SIGNATURE_BYTES);
if (!dilithium_parse_signature(&values->sign, &cbs)) {
goto err;
}
matrix_expand(&values->a_ntt, pub->rho);
uint8_t mu[MU_BYTES];
struct BORINGSSL_keccak_st keccak_ctx;
BORINGSSL_keccak_init(&keccak_ctx, boringssl_shake256);
BORINGSSL_keccak_absorb(&keccak_ctx, pub->public_key_hash,
sizeof(pub->public_key_hash));
BORINGSSL_keccak_absorb(&keccak_ctx, msg, msg_len);
BORINGSSL_keccak_squeeze(&keccak_ctx, mu, MU_BYTES);
scalar c_ntt;
scalar_sample_in_ball_vartime(&c_ntt, values->sign.c_tilde, 32);
scalar_ntt(&c_ntt);
OPENSSL_memcpy(&values->z_ntt, &values->sign.z, sizeof(values->z_ntt));
vectorl_ntt(&values->z_ntt);
matrix_mult(&values->az_ntt, &values->a_ntt, &values->z_ntt);
vectork_scale_power2_round(&values->t1_ntt, &pub->t1);
vectork_ntt(&values->t1_ntt);
vectork_mult_scalar(&values->ct1_ntt, &values->t1_ntt, &c_ntt);
vectork_sub(&values->w_approx, &values->az_ntt, &values->ct1_ntt);
vectork_inverse_ntt(&values->w_approx);
vectork_use_hint_vartime(&values->w1, &values->sign.h, &values->w_approx);
uint8_t w1_encoded[128 * K];
w1_encode(w1_encoded, &values->w1);
uint8_t c_tilde[2 * LAMBDA_BYTES];
BORINGSSL_keccak_init(&keccak_ctx, boringssl_shake256);
BORINGSSL_keccak_absorb(&keccak_ctx, mu, MU_BYTES);
BORINGSSL_keccak_absorb(&keccak_ctx, w1_encoded, 128 * K);
BORINGSSL_keccak_squeeze(&keccak_ctx, c_tilde, 2 * LAMBDA_BYTES);
uint32_t z_max = vectorl_max(&values->sign.z);
size_t h_ones = vectork_count_ones(&values->sign.h);
if (z_max < kGamma1 - BETA && h_ones <= OMEGA &&
OPENSSL_memcmp(c_tilde, values->sign.c_tilde, 2 * LAMBDA_BYTES) == 0) {
ret = 1;
}
err:
OPENSSL_free(values);
return ret;
}
/* Serialization of keys. */
int DILITHIUM_marshal_public_key(
CBB *out, const struct DILITHIUM_public_key *public_key) {
return dilithium_marshal_public_key(out,
public_key_from_external(public_key));
}
int DILITHIUM_parse_public_key(struct DILITHIUM_public_key *public_key,
CBS *in) {
struct public_key *pub = public_key_from_external(public_key);
CBS orig_in = *in;
if (!dilithium_parse_public_key(pub, in) || CBS_len(in) != 0) {
return 0;
}
// Compute pre-cached values.
BORINGSSL_keccak(pub->public_key_hash, sizeof(pub->public_key_hash),
CBS_data(&orig_in), CBS_len(&orig_in), boringssl_shake256);
return 1;
}
int DILITHIUM_marshal_private_key(
CBB *out, const struct DILITHIUM_private_key *private_key) {
return dilithium_marshal_private_key(out,
private_key_from_external(private_key));
}
int DILITHIUM_parse_private_key(struct DILITHIUM_private_key *private_key,
CBS *in) {
struct private_key *priv = private_key_from_external(private_key);
return dilithium_parse_private_key(priv, in) && CBS_len(in) == 0;
}