diff --git a/crypto/modes/internal.h b/crypto/modes/internal.h
index d12405e..caeac40 100644
--- a/crypto/modes/internal.h
+++ b/crypto/modes/internal.h
@@ -173,11 +173,6 @@
   void *key;
 };
 
-struct xts128_context {
-  void *key1, *key2;
-  block128_f block1, block2;
-};
-
 struct ccm128_context {
   union {
     uint64_t u[2];
diff --git a/decrepit/CMakeLists.txt b/decrepit/CMakeLists.txt
index a648ee5..84e5252 100644
--- a/decrepit/CMakeLists.txt
+++ b/decrepit/CMakeLists.txt
@@ -3,6 +3,7 @@
 add_subdirectory(cast)
 add_subdirectory(des)
 add_subdirectory(rsa)
+add_subdirectory(xts)
 
 add_library(
   decrepit
@@ -12,4 +13,5 @@
   $<TARGET_OBJECTS:cast>
   $<TARGET_OBJECTS:des_decrepit>
   $<TARGET_OBJECTS:rsa_decrepit>
+  $<TARGET_OBJECTS:xts>
 )
diff --git a/decrepit/xts/CMakeLists.txt b/decrepit/xts/CMakeLists.txt
new file mode 100644
index 0000000..2fe4dcf
--- /dev/null
+++ b/decrepit/xts/CMakeLists.txt
@@ -0,0 +1,9 @@
+include_directories(. ../../include)
+
+add_library(
+  xts
+
+  OBJECT
+
+  xts.c
+)
diff --git a/decrepit/xts/xts.c b/decrepit/xts/xts.c
new file mode 100644
index 0000000..cf8ad39
--- /dev/null
+++ b/decrepit/xts/xts.c
@@ -0,0 +1,295 @@
+/* ====================================================================
+ * Copyright (c) 2011 The OpenSSL Project.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. All advertising materials mentioning features or use of this
+ *    software must display the following acknowledgment:
+ *    "This product includes software developed by the OpenSSL Project
+ *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
+ *
+ * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
+ *    endorse or promote products derived from this software without
+ *    prior written permission. For written permission, please contact
+ *    openssl-core@openssl.org.
+ *
+ * 5. Products derived from this software may not be called "OpenSSL"
+ *    nor may "OpenSSL" appear in their names without prior written
+ *    permission of the OpenSSL Project.
+ *
+ * 6. Redistributions of any form whatsoever must retain the following
+ *    acknowledgment:
+ *    "This product includes software developed by the OpenSSL Project
+ *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
+ * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
+ * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ * ==================================================================== */
+
+#include <openssl/evp.h>
+
+#include <string.h>
+
+#include <openssl/aes.h>
+#include <openssl/cipher.h>
+#include <openssl/modes.h>
+
+
+#if defined(OPENSSL_X86_64) || defined(OPENSSL_X86) || defined(OPENSSL_AARCH64)
+#define STRICT_ALIGNMENT 0
+#else
+#define STRICT_ALIGNMENT 1
+#endif
+
+typedef struct xts128_context {
+  void *key1, *key2;
+  block128_f block1, block2;
+} XTS128_CONTEXT;
+
+static size_t CRYPTO_xts128_encrypt(const XTS128_CONTEXT *ctx,
+                                    const uint8_t iv[16], const uint8_t *inp,
+                                    uint8_t *out, size_t len, int enc) {
+  const union {
+    long one;
+    char little;
+  } is_endian = {1};
+  union {
+    uint64_t u[2];
+    uint32_t d[4];
+    uint8_t c[16];
+  } tweak, scratch;
+  unsigned int i;
+
+  if (len < 16) return 0;
+
+  memcpy(tweak.c, iv, 16);
+
+  (*ctx->block2)(tweak.c, tweak.c, ctx->key2);
+
+  if (!enc && (len % 16)) len -= 16;
+
+  while (len >= 16) {
+#if defined(STRICT_ALIGNMENT)
+    memcpy(scratch.c, inp, 16);
+    scratch.u[0] ^= tweak.u[0];
+    scratch.u[1] ^= tweak.u[1];
+#else
+    scratch.u[0] = ((unint64_t *)inp)[0] ^ tweak.u[0];
+    scratch.u[1] = ((unint64_t *)inp)[1] ^ tweak.u[1];
+#endif
+    (*ctx->block1)(scratch.c, scratch.c, ctx->key1);
+#if defined(STRICT_ALIGNMENT)
+    scratch.u[0] ^= tweak.u[0];
+    scratch.u[1] ^= tweak.u[1];
+    memcpy(out, scratch.c, 16);
+#else
+    ((unint64_t *)out)[0] = scratch.u[0] ^= tweak.u[0];
+    ((unint64_t *)out)[1] = scratch.u[1] ^= tweak.u[1];
+#endif
+    inp += 16;
+    out += 16;
+    len -= 16;
+
+    if (len == 0) return 1;
+
+    if (is_endian.little) {
+      unsigned int carry, res;
+
+      res = 0x87 & (((int)tweak.d[3]) >> 31);
+      carry = (unsigned int)(tweak.u[0] >> 63);
+      tweak.u[0] = (tweak.u[0] << 1) ^ res;
+      tweak.u[1] = (tweak.u[1] << 1) | carry;
+    } else {
+      size_t c;
+
+      for (c = 0, i = 0; i < 16; ++i) {
+        /*
+         * + substitutes for |, because c is 1 bit
+         */
+        c += ((size_t)tweak.c[i]) << 1;
+        tweak.c[i] = (uint8_t)c;
+        c = c >> 8;
+      }
+      tweak.c[0] ^= (uint8_t)(0x87 & (0 - c));
+    }
+  }
+  if (enc) {
+    for (i = 0; i < len; ++i) {
+      uint8_t c = inp[i];
+      out[i] = scratch.c[i];
+      scratch.c[i] = c;
+    }
+    scratch.u[0] ^= tweak.u[0];
+    scratch.u[1] ^= tweak.u[1];
+    (*ctx->block1)(scratch.c, scratch.c, ctx->key1);
+    scratch.u[0] ^= tweak.u[0];
+    scratch.u[1] ^= tweak.u[1];
+    memcpy(out - 16, scratch.c, 16);
+  } else {
+    union {
+      uint64_t u[2];
+      uint8_t c[16];
+    } tweak1;
+
+    if (is_endian.little) {
+      unsigned int carry, res;
+
+      res = 0x87 & (((int)tweak.d[3]) >> 31);
+      carry = (unsigned int)(tweak.u[0] >> 63);
+      tweak1.u[0] = (tweak.u[0] << 1) ^ res;
+      tweak1.u[1] = (tweak.u[1] << 1) | carry;
+    } else {
+      size_t c;
+
+      for (c = 0, i = 0; i < 16; ++i) {
+        /*
+         * + substitutes for |, because c is 1 bit
+         */
+        c += ((size_t)tweak.c[i]) << 1;
+        tweak1.c[i] = (uint8_t)c;
+        c = c >> 8;
+      }
+      tweak1.c[0] ^= (uint8_t)(0x87 & (0 - c));
+    }
+#if defined(STRICT_ALIGNMENT)
+    memcpy(scratch.c, inp, 16);
+    scratch.u[0] ^= tweak1.u[0];
+    scratch.u[1] ^= tweak1.u[1];
+#else
+    scratch.u[0] = ((unint64_t *)inp)[0] ^ tweak1.u[0];
+    scratch.u[1] = ((unint64_t *)inp)[1] ^ tweak1.u[1];
+#endif
+    (*ctx->block1)(scratch.c, scratch.c, ctx->key1);
+    scratch.u[0] ^= tweak1.u[0];
+    scratch.u[1] ^= tweak1.u[1];
+
+    for (i = 0; i < len; ++i) {
+      uint8_t c = inp[16 + i];
+      out[16 + i] = scratch.c[i];
+      scratch.c[i] = c;
+    }
+    scratch.u[0] ^= tweak.u[0];
+    scratch.u[1] ^= tweak.u[1];
+    (*ctx->block1)(scratch.c, scratch.c, ctx->key1);
+#if defined(STRICT_ALIGNMENT)
+    scratch.u[0] ^= tweak.u[0];
+    scratch.u[1] ^= tweak.u[1];
+    memcpy(out, scratch.c, 16);
+#else
+    ((unint64_t *)out)[0] = scratch.u[0] ^ tweak.u[0];
+    ((unint64_t *)out)[1] = scratch.u[1] ^ tweak.u[1];
+#endif
+  }
+
+  return 1;
+}
+
+typedef struct {
+  union {
+    double align;
+    AES_KEY ks;
+  } ks1, ks2;  /* AES key schedules to use */
+  XTS128_CONTEXT xts;
+} EVP_AES_XTS_CTX;
+
+static int aes_xts_init_key(EVP_CIPHER_CTX *ctx, const uint8_t *key,
+                            const uint8_t *iv, int enc) {
+  EVP_AES_XTS_CTX *xctx = ctx->cipher_data;
+  if (!iv && !key) {
+    return 1;
+  }
+
+  if (key) {
+    /* key_len is two AES keys */
+    if (enc) {
+      AES_set_encrypt_key(key, ctx->key_len * 4, &xctx->ks1.ks);
+      xctx->xts.block1 = (block128_f) AES_encrypt;
+    } else {
+      AES_set_decrypt_key(key, ctx->key_len * 4, &xctx->ks1.ks);
+      xctx->xts.block1 = (block128_f) AES_decrypt;
+    }
+
+    AES_set_encrypt_key(key + ctx->key_len / 2,
+                        ctx->key_len * 4, &xctx->ks2.ks);
+    xctx->xts.block2 = (block128_f) AES_encrypt;
+    xctx->xts.key1 = &xctx->ks1;
+  }
+
+  if (iv) {
+    xctx->xts.key2 = &xctx->ks2;
+    memcpy(ctx->iv, iv, 16);
+  }
+
+  return 1;
+}
+
+static int aes_xts_cipher(EVP_CIPHER_CTX *ctx, uint8_t *out,
+                          const uint8_t *in, size_t len) {
+  EVP_AES_XTS_CTX *xctx = ctx->cipher_data;
+  if (!xctx->xts.key1 ||
+      !xctx->xts.key2 ||
+      !out ||
+      !in ||
+      len < AES_BLOCK_SIZE ||
+      !CRYPTO_xts128_encrypt(&xctx->xts, ctx->iv, in, out, len, ctx->encrypt)) {
+    return 0;
+  }
+  return 1;
+}
+
+static int aes_xts_ctrl(EVP_CIPHER_CTX *c, int type, int arg, void *ptr) {
+  EVP_AES_XTS_CTX *xctx = c->cipher_data;
+  if (type == EVP_CTRL_COPY) {
+    EVP_CIPHER_CTX *out = ptr;
+    EVP_AES_XTS_CTX *xctx_out = out->cipher_data;
+    if (xctx->xts.key1) {
+      if (xctx->xts.key1 != &xctx->ks1) {
+        return 0;
+      }
+      xctx_out->xts.key1 = &xctx_out->ks1;
+    }
+    if (xctx->xts.key2) {
+      if (xctx->xts.key2 != &xctx->ks2) {
+        return 0;
+      }
+      xctx_out->xts.key2 = &xctx_out->ks2;
+    }
+    return 1;
+  } else if (type != EVP_CTRL_INIT) {
+    return -1;
+  }
+  /* key1 and key2 are used as an indicator both key and IV are set */
+  xctx->xts.key1 = NULL;
+  xctx->xts.key2 = NULL;
+  return 1;
+}
+
+static const EVP_CIPHER aes_256_xts = {
+    NID_aes_256_xts,     1 /* block_size */,  32 /* key_size */,
+    16 /* iv_len */,     sizeof(EVP_AES_XTS_CTX),
+    EVP_CIPH_XTS_MODE | EVP_CIPH_CUSTOM_IV | EVP_CIPH_ALWAYS_CALL_INIT |
+        EVP_CIPH_CTRL_INIT | EVP_CIPH_CUSTOM_COPY,
+    NULL /* app_data */, aes_xts_init_key,    aes_xts_cipher,
+    NULL /* cleanup */,  aes_xts_ctrl};
+
+const EVP_CIPHER *EVP_aes_256_xts(void) { return &aes_256_xts; }
diff --git a/include/openssl/cipher.h b/include/openssl/cipher.h
index eb00082..70e104d 100644
--- a/include/openssl/cipher.h
+++ b/include/openssl/cipher.h
@@ -86,6 +86,7 @@
 OPENSSL_EXPORT const EVP_CIPHER *EVP_aes_256_cbc(void);
 OPENSSL_EXPORT const EVP_CIPHER *EVP_aes_256_ctr(void);
 OPENSSL_EXPORT const EVP_CIPHER *EVP_aes_256_ofb(void);
+OPENSSL_EXPORT const EVP_CIPHER *EVP_aes_256_xts(void);
 
 /* Deprecated AES-GCM implementations that set |EVP_CIPH_FLAG_CUSTOM_CIPHER|.
  * Use |EVP_aead_aes_128_gcm| and |EVP_aead_aes_256_gcm| instead. */
@@ -341,6 +342,7 @@
 #define EVP_CIPH_OFB_MODE 0x4
 #define EVP_CIPH_CTR_MODE 0x5
 #define EVP_CIPH_GCM_MODE 0x6
+#define EVP_CIPH_XTS_MODE 0x7
 
 
 /* Cipher flags (for |EVP_CIPHER_flags|). */