cbc.c
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/*
* Copyright (C) 2015 Freie Universität 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 - cipher block chaining
*
* @author Nico von Geyso <nico.geyso@fu-berlin.de>
*
* @}
*/
#include <string.h>
#include "crypto/modes/cbc.h"
int cipher_encrypt_cbc(cipher_t* cipher, uint8_t iv[16],
uint8_t* input, size_t length, uint8_t* output)
{
size_t offset = 0;
uint8_t block_size, input_block[CIPHER_MAX_BLOCK_SIZE] = {0},
*output_block_last;
block_size = cipher_get_block_size(cipher);
if (length % block_size != 0) {
return CIPHER_ERR_INVALID_LENGTH;
}
output_block_last = iv;
do {
/* CBC-Mode: XOR plaintext with ciphertext of (n-1)-th block */
memcpy(input_block, input + offset, block_size);
for (int i = 0; i < block_size; ++i) {
input_block[i] ^= output_block_last[i];
}
if (cipher_encrypt(cipher, input_block, output + offset) != 1) {
return CIPHER_ERR_ENC_FAILED;
}
output_block_last = output + offset;
offset += block_size;
} while (offset < length);
return offset;
}
int cipher_decrypt_cbc(cipher_t* cipher, uint8_t iv[16],
uint8_t* input, size_t length, uint8_t* output)
{
size_t offset = 0;
uint8_t* input_block, *output_block, *input_block_last, block_size;
block_size = cipher_get_block_size(cipher);
if (length % block_size != 0) {
return CIPHER_ERR_INVALID_LENGTH;
}
input_block_last = iv;
do {
input_block = input + offset;
output_block = output + offset;
if (cipher_decrypt(cipher, input_block, output_block) != 1) {
return CIPHER_ERR_DEC_FAILED;
}
/* CBC-Mode: XOR plaintext with ciphertext of (n-1)-th block */
for (uint8_t i = 0; i < block_size; ++i) {
output_block[i] ^= input_block_last[i];
}
input_block_last = input_block;
offset += block_size;
} while (offset < length);
return offset;
}