/** Decrypt the 16 byte block using AES in XEX mode. This uses an arbitrary
* encryption key.
* \param out The resulting plaintext will be written to here. This must be
* a byte array with space for 16 bytes.
* \param in The source ciphertext. This must be a byte array containing the
* 16 byte ciphertext.
* \param n See xexEncryptInternal().
* \param seq See xexEncryptInternal().
* \param tweak_key See xexEncryptInternal().
* \param encrypt_key See xexEncryptInternal().
*/
static void xexDecryptInternal(uint8_t *out, uint8_t *in, uint8_t *n, uint8_t seq, uint8_t *tweak_key, uint8_t *encrypt_key)
{
xexEnDecrypt(out, in, n, seq, tweak_key, encrypt_key, true);
}
/** Encrypt one 16 byte block using AES in XEX mode.
* \param out The resulting ciphertext will be written to here. This must be
* a byte array with space for 16 bytes.
* \param in The source plaintext. This must be a byte array containing the
* 16 byte plaintext.
* \param n A 128 bit number which specifies the number of the data
* unit (whatever a data unit is defined to be). This should be a
* byte array of 16 bytes, with the 128 bit number in unsigned,
* little-endian multi-precision format.
* \param seq Specifies the block within the data unit.
* \param tweak_key A 128 bit AES key.
* \param encrypt_key Another 128 bit AES key. This must be independent of
* tweak_key.
* \warning Don't use seq = 0, as this presents a security
* vulnerability (albeit a convoluted one). For more details about
* the seq = 0 issue, see section 6 ("Security of XEX") of
* Rogaway's paper (reference at the top of this file).
*/
static void xexEncrypt(uint8_t *out, uint8_t *in, uint8_t *n, uint8_t seq, uint8_t *tweak_key, uint8_t *encrypt_key)
{
xexEnDecrypt(out, in, n, seq, tweak_key, encrypt_key, 0);
}
