1f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project/* LibTomCrypt, modular cryptographic library -- Tom St Denis 2f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project * 3f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project * LibTomCrypt is a library that provides various cryptographic 4f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project * algorithms in a highly modular and flexible manner. 5f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project * 6f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project * The library is free for all purposes without any express 7f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project * guarantee it works. 8f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project * 9f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project * Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.com 10f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project */ 11f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project#include "tomcrypt.h" 12f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project 13f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project/** 14f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project @file cbc_decrypt.c 15f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project CBC implementation, encrypt block, Tom St Denis 16f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project*/ 17f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project 18f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project 19f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project#ifdef LTC_CBC_MODE 20f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project 21f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project/** 22f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project CBC decrypt 23f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project @param ct Ciphertext 24f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project @param pt [out] Plaintext 25f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project @param len The number of bytes to process (must be multiple of block length) 26f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project @param cbc CBC state 27f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project @return CRYPT_OK if successful 28f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project*/ 29f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Projectint cbc_decrypt(const unsigned char *ct, unsigned char *pt, unsigned long len, symmetric_CBC *cbc) 30f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project{ 31f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project int x, err; 32f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project unsigned char tmp[16]; 33f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project#ifdef LTC_FAST 34f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project LTC_FAST_TYPE tmpy; 35f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project#else 36f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project unsigned char tmpy; 37f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project#endif 38f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project 39f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project LTC_ARGCHK(pt != NULL); 40f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project LTC_ARGCHK(ct != NULL); 41f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project LTC_ARGCHK(cbc != NULL); 42f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project 43f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project if ((err = cipher_is_valid(cbc->cipher)) != CRYPT_OK) { 44f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project return err; 45f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project } 46f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project 47f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project /* is blocklen valid? */ 48f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project if (cbc->blocklen < 1 || cbc->blocklen > (int)sizeof(cbc->IV)) { 49f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project return CRYPT_INVALID_ARG; 50f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project } 51f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project 52f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project if (len % cbc->blocklen) { 53f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project return CRYPT_INVALID_ARG; 54f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project } 55f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project#ifdef LTC_FAST 56f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project if (cbc->blocklen % sizeof(LTC_FAST_TYPE)) { 57f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project return CRYPT_INVALID_ARG; 58f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project } 59f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project#endif 60f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project 61f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project if (cipher_descriptor[cbc->cipher].accel_cbc_decrypt != NULL) { 62f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project return cipher_descriptor[cbc->cipher].accel_cbc_decrypt(ct, pt, len / cbc->blocklen, cbc->IV, &cbc->key); 63f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project } else { 64f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project while (len) { 65f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project /* decrypt */ 66f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project if ((err = cipher_descriptor[cbc->cipher].ecb_decrypt(ct, tmp, &cbc->key)) != CRYPT_OK) { 67f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project return err; 68f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project } 69f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project 70f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project /* xor IV against plaintext */ 71f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project #if defined(LTC_FAST) 72f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project for (x = 0; x < cbc->blocklen; x += sizeof(LTC_FAST_TYPE)) { 73f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project tmpy = *((LTC_FAST_TYPE*)((unsigned char *)cbc->IV + x)) ^ *((LTC_FAST_TYPE*)((unsigned char *)tmp + x)); 74f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project *((LTC_FAST_TYPE*)((unsigned char *)cbc->IV + x)) = *((LTC_FAST_TYPE*)((unsigned char *)ct + x)); 75f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project *((LTC_FAST_TYPE*)((unsigned char *)pt + x)) = tmpy; 76f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project } 77f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project #else 78f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project for (x = 0; x < cbc->blocklen; x++) { 79f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project tmpy = tmp[x] ^ cbc->IV[x]; 80f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project cbc->IV[x] = ct[x]; 81f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project pt[x] = tmpy; 82f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project } 83f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project #endif 84f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project 85f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project ct += cbc->blocklen; 86f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project pt += cbc->blocklen; 87f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project len -= cbc->blocklen; 88f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project } 89f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project } 90f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project return CRYPT_OK; 91f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project} 92f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project 93f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project#endif 94f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project 95f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project/* $Source: /cvs/libtom/libtomcrypt/src/modes/cbc/cbc_decrypt.c,v $ */ 96f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project/* $Revision: 1.15 $ */ 97f7fc46c63fdc8f39234fea409b8dbe116d73ebf8The Android Open Source Project/* $Date: 2006/11/21 00:18:23 $ */ 98