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/* 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@iahu.ca, http://libtomcrypt.org
*/
#include "mycrypt.h"
#ifdef CTR
int ctr_encrypt(const unsigned char *pt, unsigned char *ct, unsigned long len, symmetric_CTR *ctr)
{
int x, err;
_ARGCHK(pt != NULL);
_ARGCHK(ct != NULL);
_ARGCHK(ctr != NULL);
if ((err = cipher_is_valid(ctr->cipher)) != CRYPT_OK) {
return err;
}
/* is blocklen/padlen valid? */
if (ctr->blocklen < 0 || ctr->blocklen > (int)sizeof(ctr->ctr) ||
ctr->padlen < 0 || ctr->padlen > (int)sizeof(ctr->pad)) {
return CRYPT_INVALID_ARG;
}
while (len-- > 0) {
/* is the pad empty? */
if (ctr->padlen == ctr->blocklen) {
/* increment counter */
if (ctr->mode == 0) {
/* little-endian */
for (x = 0; x < ctr->blocklen; x++) {
ctr->ctr[x] = (ctr->ctr[x] + (unsigned char)1) & (unsigned char)255;
if (ctr->ctr[x] != (unsigned char)0) {
break;
}
}
} else {
/* big-endian */
for (x = ctr->blocklen-1; x >= 0; x--) {
ctr->ctr[x] = (ctr->ctr[x] + (unsigned char)1) & (unsigned char)255;
if (ctr->ctr[x] != (unsigned char)0) {
break;
}
}
}
/* encrypt it */
cipher_descriptor[ctr->cipher].ecb_encrypt(ctr->ctr, ctr->pad, &ctr->key);
ctr->padlen = 0;
}
*ct++ = *pt++ ^ ctr->pad[ctr->padlen++];
}
return CRYPT_OK;
}
#endif
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