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| -rw-r--r-- | cbc.c | 78 | ||||
| -rw-r--r-- | cbc.h | 49 |
2 files changed, 127 insertions, 0 deletions
@@ -0,0 +1,78 @@ +/* cbc.c + * + * Cipher block chaining mode. + */ + +/* nettle, low-level cryptographics library + * + * Copyright (C) 2001 Niels Möller + * + * The nettle library is free software; you can redistribute it and/or modify + * it under the terms of the GNU Lesser General Public License as published by + * the Free Software Foundation; either version 2.1 of the License, or (at your + * option) any later version. + * + * The nettle library is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY + * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public + * License for more details. + * + * You should have received a copy of the GNU Lesser General Public License + * along with the nettle library; see the file COPYING.LIB. If not, write to + * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, + * MA 02111-1307, USA. + */ + +#include "cbc.h" + +#include <assert.h> + +void +cbc_encrypt(void *ctx, void (*f)(void *ctx, + unsigned length, uint8_t *dst, + const uint8_t *src), + unsigned block_size, uint8_t *iv, + unsigned length, uint8_t *dst, + const uint8_t *src) +{ + assert(!(length % block_size)); + + for ( ; length; length -= block_size, src += block_size, dst += block_size) + { + memxor(iv, src, block_size); + f(ctx, dst, src, block_size); + memcpy(iv, dst, block_size); + } +} + +void +cbc_decrypt(void *ctx, void (*f)(void *ctx, + unsigned length, uint8_t *dst, + const uint8_t *src), + unsigned block_size, uint8_t *iv, + unsigned length, uint8_t *dst, + const uint8_t *src) +{ + assert(!(length % block_size)); + + if (!length) + return; + + if (src == dst) + { + /* Keep a copy of the ciphertext. */ + /* FIXME: If length is large enough, allocate a smaller buffer + * and process one buffer size at a time */ + uint8_t *tmp = alloca(length); + memcpy(tmp, src, length); + src = tmp; + } + + /* Decrypt in ECB mode */ + f(ctx, dst, src, length); + + /* XOR the cryptotext, shifted one block */ + memxor(dst, iv, block_size); + memxor(dst + block_size, src, length - block_size); + memcpy(iv, src + length - block_size, block_size); +} @@ -0,0 +1,49 @@ +/* cbc.h + * + * Cipher block chaining mode. + */ + +/* nettle, low-level cryptographics library + * + * Copyright (C) 2001 Niels Möller + * + * The nettle library is free software; you can redistribute it and/or modify + * it under the terms of the GNU Lesser General Public License as published by + * the Free Software Foundation; either version 2.1 of the License, or (at your + * option) any later version. + * + * The nettle library is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY + * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public + * License for more details. + * + * You should have received a copy of the GNU Lesser General Public License + * along with the nettle library; see the file COPYING.LIB. If not, write to + * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, + * MA 02111-1307, USA. + */ + +#ifndef NETTLE_CBC_H_INCLUDED +#define NETTLE_CBC_H_INCLUDED + +#include <inttypes.h> + +/* Uses a void * for cipher contexts. It's hard to be type safe. */ + +void +cbc_encrypt(void *ctx, void (*f)(void *ctx, + unsigned length, uint8_t *dst, + const uint8_t *src), + unsigned block_size, uint8_t *iv, + unsigned length, uint8_t *dst, + const uint8_t *src); + +void +cbc_decrypt(void *ctx, void (*f)(void *ctx, + unsigned length, uint8_t *dst, + const uint8_t *src), + unsigned block_size, uint8_t *iv, + unsigned length, uint8_t *dst, + const uint8_t *src); + +#endif /* NETTLE_CBC_H_INCLUDED */ |