Implement AES-XEX mode
XEX mode, known as "xor-encrypt-xor", is the simple case of the XTS
mode, known as "XEX with ciphertext stealing". When the buffers to be
encrypted/decrypted have a length divisible by the length of a standard
AES block (16), XTS is exactly like XEX.
diff --git a/include/mbedtls/aes.h b/include/mbedtls/aes.h
index e48981a..652281c 100644
--- a/include/mbedtls/aes.h
+++ b/include/mbedtls/aes.h
@@ -213,6 +213,30 @@
unsigned char *output );
#endif /* MBEDTLS_CIPHER_MODE_CBC */
+#if defined(MBEDTLS_CIPHER_MODE_XEX)
+/**
+ * \brief AES-XEX buffer encryption/decryption
+ * Length should be a multiple of the block size (16 bytes)
+ *
+ * \param crypt_ctx AES context for encrypting data
+ * \param tweak_ctx AES context for xor-ing with data
+ * \param mode MBEDTLS_AES_ENCRYPT or MBEDTLS_AES_DECRYPT
+ * \param length length of the input data
+ * \param iv initialization vector
+ * \param input buffer holding the input data
+ * \param output buffer holding the output data
+ *
+ * \return 0 if successful, or MBEDTLS_ERR_AES_INVALID_INPUT_LENGTH
+ */
+int mbedtls_aes_crypt_xex( mbedtls_aes_context *crypt_ctx,
+ mbedtls_aes_context *tweak_ctx,
+ int mode,
+ size_t length,
+ unsigned char iv[16],
+ const unsigned char *input,
+ unsigned char *output );
+#endif /* MBEDTLS_CIPHER_MODE_XEX */
+
#if defined(MBEDTLS_CIPHER_MODE_CFB)
/**
* \brief This function performs an AES-CFB128 encryption or decryption