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/*
* Copyright (C) 2015 Freie Universitรคt Berlin
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @ingroup sys_crypto_modes
* @{
*
* @file
* @brief Crypto mode - Counter
*
* @author Nico von Geyso <nico.geyso@fu-berlin.de>
*
* @}
*/
#include "crypto/helper.h"
#include "crypto/modes/ctr.h"
int cipher_encrypt_ctr(cipher_t* cipher, uint8_t nonce_counter[16],
uint8_t nonce_len, uint8_t* input, size_t length,
uint8_t* output)
{
size_t offset = 0;
uint8_t stream_block[16] = {0}, block_size;
block_size = cipher_get_block_size(cipher);
do {
uint8_t block_size_input;
if (cipher_encrypt(cipher, nonce_counter, stream_block) != 1) {
return CIPHER_ERR_ENC_FAILED;
}
block_size_input = (length - offset > block_size) ?
block_size : length - offset;
for (uint8_t i = 0; i < block_size_input; ++i) {
output[offset + i] = stream_block[i] ^ input[offset + i];
}
offset += block_size_input;
crypto_block_inc_ctr(nonce_counter, block_size - nonce_len);
} while (offset < length);
return offset;
}
int cipher_decrypt_ctr(cipher_t* cipher, uint8_t nonce_counter[16],
uint8_t nonce_len, uint8_t* input, size_t length,
uint8_t* output)
{
return cipher_encrypt_ctr(cipher, nonce_counter, nonce_len, input,
length, output);
}
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