aes: xts: Add new context structure
Add a new context structure for XTS. Adjust the API for XTS to use the new
context structure, including tests suites and the benchmark program. Update
Doxgen documentation accordingly.
diff --git a/library/aes.c b/library/aes.c
index 9e7b248..ed260a9 100644
--- a/library/aes.c
+++ b/library/aes.c
@@ -521,6 +521,20 @@
mbedtls_platform_zeroize( ctx, sizeof( mbedtls_aes_context ) );
}
+#if defined(MBEDTLS_CIPHER_MODE_XTS)
+void mbedtls_aes_xts_init( mbedtls_aes_xts_context *ctx )
+{
+ mbedtls_aes_init( &ctx->crypt );
+ mbedtls_aes_init( &ctx->tweak );
+}
+
+void mbedtls_aes_xts_free( mbedtls_aes_xts_context *ctx )
+{
+ mbedtls_aes_free( &ctx->crypt );
+ mbedtls_aes_free( &ctx->tweak );
+}
+#endif /* MBEDTLS_CIPHER_MODE_XTS */
+
/*
* AES key schedule (encryption)
*/
@@ -702,6 +716,78 @@
return( ret );
}
+
+#if defined(MBEDTLS_CIPHER_MODE_XTS)
+static int mbedtls_aes_xts_decode_keys( const unsigned char *key,
+ unsigned int keybits,
+ const unsigned char **key1,
+ unsigned int *key1bits,
+ const unsigned char **key2,
+ unsigned int *key2bits )
+{
+ const unsigned int half_keybits = keybits / 2;
+ const unsigned int half_keybytes = half_keybits / 8;
+
+ switch( keybits )
+ {
+ case 256: break;
+ case 512: break;
+ default : return( MBEDTLS_ERR_AES_INVALID_KEY_LENGTH );
+ }
+
+ *key1bits = half_keybits;
+ *key2bits = half_keybits;
+ *key1 = &key[0];
+ *key2 = &key[half_keybytes];
+
+ return 0;
+}
+
+int mbedtls_aes_xts_setkey_enc( mbedtls_aes_xts_context *ctx,
+ const unsigned char *key,
+ unsigned int keybits)
+{
+ int ret;
+ const unsigned char *key1, *key2;
+ unsigned int key1bits, key2bits;
+
+ ret = mbedtls_aes_xts_decode_keys( key, keybits, &key1, &key1bits,
+ &key2, &key2bits );
+ if( ret != 0 )
+ return( ret );
+
+ /* Set the tweak key. Always set tweak key for the encryption mode. */
+ ret = mbedtls_aes_setkey_enc( &ctx->tweak, key2, key2bits );
+ if( ret != 0 )
+ return( ret );
+
+ /* Set crypt key for encryption. */
+ return mbedtls_aes_setkey_enc( &ctx->crypt, key1, key1bits );
+}
+
+int mbedtls_aes_xts_setkey_dec( mbedtls_aes_xts_context *ctx,
+ const unsigned char *key,
+ unsigned int keybits)
+{
+ int ret;
+ const unsigned char *key1, *key2;
+ unsigned int key1bits, key2bits;
+
+ ret = mbedtls_aes_xts_decode_keys( key, keybits, &key1, &key1bits,
+ &key2, &key2bits );
+ if( ret != 0 )
+ return( ret );
+
+ /* Set the tweak key. Always set tweak key for encryption. */
+ ret = mbedtls_aes_setkey_enc( &ctx->tweak, key2, key2bits );
+ if( ret != 0 )
+ return( ret );
+
+ /* Set crypt key for decryption. */
+ return mbedtls_aes_setkey_dec( &ctx->crypt, key1, key1bits );
+}
+#endif /* MBEDTLS_CIPHER_MODE_XTS */
+
#endif /* !MBEDTLS_AES_SETKEY_DEC_ALT */
#define AES_FROUND(X0,X1,X2,X3,Y0,Y1,Y2,Y3) \
@@ -1042,13 +1128,12 @@
/*
* AES-XTS buffer encryption/decryption
*/
-int mbedtls_aes_crypt_xts( mbedtls_aes_context *crypt_ctx,
- mbedtls_aes_context *tweak_ctx,
- int mode,
- size_t bits_length,
- unsigned char iv[16],
- const unsigned char *input,
- unsigned char *output )
+int mbedtls_aes_crypt_xts( mbedtls_aes_xts_context *ctx,
+ int mode,
+ size_t bits_length,
+ const unsigned char iv[16],
+ const unsigned char *input,
+ unsigned char *output )
{
union xts_buf128 {
uint8_t u8[16];
@@ -1075,7 +1160,7 @@
return( MBEDTLS_ERR_AES_INVALID_INPUT_LENGTH );
- mbedtls_aes_crypt_ecb( tweak_ctx, MBEDTLS_AES_ENCRYPT, iv, t_buf.u8 );
+ mbedtls_aes_crypt_ecb( &ctx->tweak, MBEDTLS_AES_ENCRYPT, iv, t_buf.u8 );
if( mode == MBEDTLS_AES_DECRYPT && remn )
{
@@ -1096,7 +1181,7 @@
scratch.u64[1] = (uint64_t)( inbuf->u64[1] ^ t_buf.u64[1] );
/* CC <- E(Key2,PP) */
- mbedtls_aes_crypt_ecb( crypt_ctx, mode, scratch.u8, outbuf->u8 );
+ mbedtls_aes_crypt_ecb( &ctx->crypt, mode, scratch.u8, outbuf->u8 );
/* C <- T xor CC */
outbuf->u64[0] = (uint64_t)( outbuf->u64[0] ^ t_buf.u64[0] );
@@ -1127,7 +1212,7 @@
scratch.u64[1] = (uint64_t)( cts_scratch.u64[1] ^ t_buf.u64[1] );
/* CC <- E(Key2,PP) */
- mbedtls_aes_crypt_ecb( crypt_ctx, mode, scratch.u8, scratch.u8 );
+ mbedtls_aes_crypt_ecb( &ctx->crypt, mode, scratch.u8, scratch.u8 );
/* C <- T xor CC */
outbuf[nblk - 1].u64[0] = (uint64_t)( scratch.u64[0] ^ t_buf.u64[0] );
@@ -1148,7 +1233,7 @@
scratch.u64[1] = (uint64_t)( inbuf[nblk - 1].u64[1] ^ t_buf.u64[1] );
/* CC <- E(Key2,PP) */
- mbedtls_aes_crypt_ecb( crypt_ctx, mode, scratch.u8, scratch.u8 );
+ mbedtls_aes_crypt_ecb( &ctx->crypt, mode, scratch.u8, scratch.u8 );
/* C <- T xor CC */
cts_scratch.u64[0] = (uint64_t)( scratch.u64[0] ^ t_buf.u64[0] );
@@ -1165,7 +1250,7 @@
scratch.u64[1] = (uint64_t)( inbuf[nblk - 1].u64[1] ^ cts_t_buf.u64[1] );
/* CC <- E(Key2,PP) */
- mbedtls_aes_crypt_ecb( crypt_ctx, mode, scratch.u8, scratch.u8 );
+ mbedtls_aes_crypt_ecb( &ctx->crypt, mode, scratch.u8, scratch.u8 );
/* C <- T xor CC */
outbuf[nblk - 1].u64[0] = (uint64_t)( scratch.u64[0] ^ cts_t_buf.u64[0] );
