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added libtomcrypt-1.01

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This commit is contained in:
Tom St Denis
2005-04-17 11:37:13 +00:00
committed by Steffen Jaeckel
parent bfc2f5b078
commit 6ac9952498
259 changed files with 7203 additions and 2286 deletions
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src/modes/cbc/cbc_decrypt.c
+54 -32
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@@ -6,64 +6,86 @@
* The library is free for all purposes without any express
* guarantee it works.
*
* Tom St Denis, tomstdenis@iahu.ca, http://libtomcrypt.org
* Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.org
*/
#include "tomcrypt.h"
/**
@file cbc_decrypt.c
CBC implementation, decrypt block, Tom St Denis
CBC implementation, encrypt block, Tom St Denis
*/
#ifdef CBC
/**
CBC decrypt
@param ct Ciphertext
@param pt [out] Plaintext
@param cbc CBC state
@return CRYPT_OK if successful
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, symmetric_CBC *cbc)
int cbc_decrypt(const unsigned char *ct, unsigned char *pt, unsigned long len, symmetric_CBC *cbc)
{
int x, err;
unsigned char tmp[MAXBLOCKSIZE], tmp2[MAXBLOCKSIZE];
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(pt != NULL);
LTC_ARGCHK(ct != NULL);
LTC_ARGCHK(cbc != NULL);
/* decrypt the block from ct into tmp */
if ((err = cipher_is_valid(cbc->cipher)) != CRYPT_OK) {
return err;
}
LTC_ARGCHK(cipher_descriptor[cbc->cipher].ecb_decrypt != NULL);
/* is blocklen valid? */
if (cbc->blocklen < 0 || cbc->blocklen > (int)sizeof(cbc->IV)) {
return CRYPT_INVALID_ARG;
}
}
/* decrypt and xor IV against the plaintext of the previous step */
cipher_descriptor[cbc->cipher].ecb_decrypt(ct, tmp, &cbc->key);
for (x = 0; x < cbc->blocklen; x++) {
/* copy CT in case ct == pt */
tmp2[x] = ct[x];
/* actually decrypt the byte */
pt[x] = tmp[x] ^ cbc->IV[x];
if (len % cbc->blocklen) {
return CRYPT_INVALID_ARG;
}
/* replace IV with this current ciphertext */
for (x = 0; x < cbc->blocklen; x++) {
cbc->IV[x] = tmp2[x];
#ifdef LTC_FAST
if (len % sizeof(LTC_FAST_TYPE)) {
return CRYPT_INVALID_ARG;
}
#endif
if (cipher_descriptor[cbc->cipher].accel_cbc_decrypt != NULL) {
cipher_descriptor[cbc->cipher].accel_cbc_decrypt(ct, pt, len / cbc->blocklen, cbc->IV, &cbc->key);
} else {
while (len) {
/* decrypt */
cipher_descriptor[cbc->cipher].ecb_decrypt(ct, tmp, &cbc->key);
/* 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;
}
}
#ifdef LTC_CLEAN_STACK
zeromem(tmp, sizeof(tmp));
zeromem(tmp2, sizeof(tmp2));
#endif
return CRYPT_OK;
}
#endif