diff options
Diffstat (limited to 'core/lib/libtomcrypt/src/modes/cbc/cbc_decrypt.c')
| -rw-r--r-- | core/lib/libtomcrypt/src/modes/cbc/cbc_decrypt.c | 124 |
1 files changed, 124 insertions, 0 deletions
diff --git a/core/lib/libtomcrypt/src/modes/cbc/cbc_decrypt.c b/core/lib/libtomcrypt/src/modes/cbc/cbc_decrypt.c new file mode 100644 index 0000000..8ab2542 --- /dev/null +++ b/core/lib/libtomcrypt/src/modes/cbc/cbc_decrypt.c @@ -0,0 +1,124 @@ +/* + * Copyright (c) 2001-2007, Tom St Denis + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are met: + * + * 1. Redistributions of source code must retain the above copyright notice, + * this list of conditions and the following disclaimer. + * + * 2. Redistributions in binary form must reproduce the above copyright notice, + * this list of conditions and the following disclaimer in the documentation + * and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" + * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE + * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR + * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF + * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS + * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN + * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + */ + +/* LibTomCrypt, modular cryptographic library -- Tom St Denis + * + * LibTomCrypt is a library that provides various cryptographic + * algorithms in a highly modular and flexible manner. + * + * The library is free for all purposes without any express + * guarantee it works. + * + * Tom St Denis, tomstdenis@gmail.com, http://libtom.org + */ +#include "tomcrypt.h" + +/** + @file cbc_decrypt.c + CBC implementation, encrypt block, Tom St Denis +*/ + + +#ifdef LTC_CBC_MODE + +/** + CBC decrypt + @param ct Ciphertext + @param pt [out] Plaintext + @param len The number of bytes to process (must be multiple of block length) + @param cbc CBC state + @return CRYPT_OK if successful +*/ +int cbc_decrypt(const unsigned char *ct, unsigned char *pt, unsigned long len, symmetric_CBC *cbc) +{ + int x, err; + unsigned char tmp[16]; +#ifdef LTC_FAST + LTC_FAST_TYPE tmpy; +#else + unsigned char tmpy; +#endif + + LTC_ARGCHK(pt != NULL); + LTC_ARGCHK(ct != NULL); + LTC_ARGCHK(cbc != NULL); + + if ((err = cipher_is_valid(cbc->cipher)) != CRYPT_OK) { + return err; + } + + /* is blocklen valid? */ + if (cbc->blocklen < 1 || cbc->blocklen > (int)sizeof(cbc->IV)) { + return CRYPT_INVALID_ARG; + } + + if (len % cbc->blocklen) { + return CRYPT_INVALID_ARG; + } +#ifdef LTC_FAST + if (cbc->blocklen % sizeof(LTC_FAST_TYPE)) { + return CRYPT_INVALID_ARG; + } +#endif + + if (cipher_descriptor[cbc->cipher]->accel_cbc_decrypt != NULL) { + return cipher_descriptor[cbc->cipher]->accel_cbc_decrypt(ct, pt, len / cbc->blocklen, cbc->IV, &cbc->key); + } else { + while (len) { + /* decrypt */ + if ((err = cipher_descriptor[cbc->cipher]->ecb_decrypt(ct, tmp, &cbc->key)) != CRYPT_OK) { + return err; + } + + /* xor IV against plaintext */ + #if defined(LTC_FAST) + for (x = 0; x < cbc->blocklen; x += sizeof(LTC_FAST_TYPE)) { + tmpy = *((LTC_FAST_TYPE*)((unsigned char *)cbc->IV + x)) ^ *((LTC_FAST_TYPE*)((unsigned char *)tmp + x)); + *((LTC_FAST_TYPE*)((unsigned char *)cbc->IV + x)) = *((LTC_FAST_TYPE*)((unsigned char *)ct + x)); + *((LTC_FAST_TYPE*)((unsigned char *)pt + x)) = tmpy; + } + #else + for (x = 0; x < cbc->blocklen; x++) { + tmpy = tmp[x] ^ cbc->IV[x]; + cbc->IV[x] = ct[x]; + pt[x] = tmpy; + } + #endif + + ct += cbc->blocklen; + pt += cbc->blocklen; + len -= cbc->blocklen; + } + } + return CRYPT_OK; +} + +#endif + +/* $Source: /cvs/libtom/libtomcrypt/src/modes/cbc/cbc_decrypt.c,v $ */ +/* $Revision: 1.16 $ */ +/* $Date: 2006/12/28 01:27:24 $ */ |