Implement AES-XTS mode
XTS mode is fully known as "xor-encrypt-xor with ciphertext-stealing".
This is the generalization of the XEX mode.
This implementation is limited to an 8-bits (1 byte) boundary, which
doesn't seem to be what was thought considering some test vectors [1].
This commit comes with tests, extracted from [1], and benchmarks.
Although, benchmarks aren't really nice here, as they work with a buffer
of a multiple of 16 bytes, which isn't a challenge for XTS compared to
XEX.
[1] http://csrc.nist.gov/groups/STM/cavp/documents/aes/XTSTestVectors.zip
diff --git a/tests/suites/test_suite_aes.function b/tests/suites/test_suite_aes.function
index 947976a..71633dd 100644
--- a/tests/suites/test_suite_aes.function
+++ b/tests/suites/test_suite_aes.function
@@ -225,6 +225,80 @@
}
/* END_CASE */
+/* BEGIN_CASE depends_on:MBEDTLS_CIPHER_MODE_XTS */
+void aes_encrypt_xts( char *hex_key_string, char *hex_iv_string,
+ char *hex_src_string, char *hex_dst_string,
+ int data_unit_len, int xts_result )
+{
+ unsigned char key_str[100] = { 0, };
+ unsigned char iv_str[100] = { 0, };
+ unsigned char src_str[100] = { 0, };
+ unsigned char dst_str[100] = { 0, };
+ unsigned char output[100] = { 0, };
+ mbedtls_aes_context crypt_ctx, tweak_ctx;
+ int key_len, data_len;
+
+ mbedtls_aes_init( &crypt_ctx );
+ mbedtls_aes_init( &tweak_ctx );
+
+ key_len = unhexify( key_str, hex_key_string );
+ unhexify( iv_str, hex_iv_string );
+ data_len = unhexify( src_str, hex_src_string );
+
+ mbedtls_aes_setkey_enc( &crypt_ctx, key_str, ( key_len * 8 ) / 2 );
+ mbedtls_aes_setkey_enc( &tweak_ctx, key_str + key_len / 2, ( key_len * 8 ) / 2 );
+
+ TEST_ASSERT( mbedtls_aes_crypt_xts( &crypt_ctx, &tweak_ctx, MBEDTLS_AES_ENCRYPT, data_unit_len, iv_str, src_str, output ) == xts_result );
+ if( xts_result == 0 )
+ {
+ hexify( dst_str, output, data_len );
+
+ TEST_ASSERT( strcmp( (char *) dst_str, hex_dst_string ) == 0 );
+ }
+
+exit:
+ mbedtls_aes_free( &crypt_ctx );
+ mbedtls_aes_free( &tweak_ctx );
+}
+/* END_CASE */
+
+/* BEGIN_CASE depends_on:MBEDTLS_CIPHER_MODE_XTS */
+void aes_decrypt_xts( char *hex_key_string, char *hex_iv_string,
+ char *hex_src_string, char *hex_dst_string,
+ int data_unit_len, int xts_result )
+{
+ unsigned char key_str[100] = { 0, };
+ unsigned char iv_str[100] = { 0, };
+ unsigned char src_str[100] = { 0, };
+ unsigned char dst_str[100] = { 0, };
+ unsigned char output[100] = { 0, };
+ mbedtls_aes_context crypt_ctx, tweak_ctx;
+ int key_len, data_len;
+
+ mbedtls_aes_init( &crypt_ctx );
+ mbedtls_aes_init( &tweak_ctx );
+
+ key_len = unhexify( key_str, hex_key_string );
+ unhexify( iv_str, hex_iv_string );
+ data_len = unhexify( src_str, hex_src_string );
+
+ mbedtls_aes_setkey_dec( &crypt_ctx, key_str, ( key_len * 8 ) / 2 );
+ mbedtls_aes_setkey_enc( &tweak_ctx, key_str + key_len / 2, ( key_len * 8 ) / 2 );
+
+ TEST_ASSERT( mbedtls_aes_crypt_xts( &crypt_ctx, &tweak_ctx, MBEDTLS_AES_DECRYPT, data_unit_len, iv_str, src_str, output ) == xts_result );
+ if( xts_result == 0 )
+ {
+ hexify( dst_str, output, data_len );
+
+ TEST_ASSERT( strcmp( (char *) dst_str, hex_dst_string ) == 0 );
+ }
+
+exit:
+ mbedtls_aes_free( &crypt_ctx );
+ mbedtls_aes_free( &tweak_ctx );
+}
+/* END_CASE */
+
/* BEGIN_CASE depends_on:MBEDTLS_CIPHER_MODE_CFB */
void aes_encrypt_cfb128( char *hex_key_string, char *hex_iv_string,
char *hex_src_string, char *hex_dst_string )