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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@gmail.com, http://libtom.org
*/
#include "tomcrypt.h"
/**
@file ctr_encrypt.c
CTR implementation, encrypt data, Tom St Denis
*/
#ifdef LTC_CTR_MODE
/**
CTR encrypt
@param pt Plaintext
@param ct [out] Ciphertext
@param len Length of plaintext (octets)
@param ctr CTR state
@return CRYPT_OK if successful
*/
int ctr_encrypt(const unsigned char *pt, unsigned char *ct, unsigned long len, symmetric_CTR *ctr)
{
int x, err;
LTC_ARGCHK(pt != NULL);
LTC_ARGCHK(ct != NULL);
LTC_ARGCHK(ctr != NULL);
if ((err = cipher_is_valid(ctr->cipher)) != CRYPT_OK) {
return err;
}
/* is blocklen/padlen valid? */
if (ctr->blocklen < 1 || ctr->blocklen > (int)sizeof(ctr->ctr) ||
ctr->padlen < 0 || ctr->padlen > (int)sizeof(ctr->pad)) {
return CRYPT_INVALID_ARG;
}
#ifdef LTC_FAST
if (ctr->blocklen % sizeof(LTC_FAST_TYPE)) {
return CRYPT_INVALID_ARG;
}
#endif
/* handle acceleration only if pad is empty, accelerator is present and length is >= a block size */
if ((ctr->padlen == ctr->blocklen) && cipher_descriptor[ctr->cipher].accel_ctr_encrypt != NULL && (len >= (unsigned long)ctr->blocklen)) {
if ((err = cipher_descriptor[ctr->cipher].accel_ctr_encrypt(pt, ct, len/ctr->blocklen, ctr->ctr, ctr->mode, &ctr->key)) != CRYPT_OK) {
return err;
}
len %= ctr->blocklen;
}
while (len) {
/* is the pad empty? */
if (ctr->padlen == ctr->blocklen) {
/* increment counter */
if (ctr->mode == CTR_COUNTER_LITTLE_ENDIAN) {
/* little-endian */
for (x = 0; x < ctr->ctrlen; 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 >= ctr->ctrlen; x--) {
ctr->ctr[x] = (ctr->ctr[x] + (unsigned char)1) & (unsigned char)255;
if (ctr->ctr[x] != (unsigned char)0) {
break;
}
}
}
/* encrypt it */
if ((err = cipher_descriptor[ctr->cipher].ecb_encrypt(ctr->ctr, ctr->pad, &ctr->key)) != CRYPT_OK) {
return err;
}
ctr->padlen = 0;
}
#ifdef LTC_FAST
if (ctr->padlen == 0 && len >= (unsigned long)ctr->blocklen) {
for (x = 0; x < ctr->blocklen; x += sizeof(LTC_FAST_TYPE)) {
*((LTC_FAST_TYPE*)((unsigned char *)ct + x)) = *((LTC_FAST_TYPE*)((unsigned char *)pt + x)) ^
*((LTC_FAST_TYPE*)((unsigned char *)ctr->pad + x));
}
pt += ctr->blocklen;
ct += ctr->blocklen;
len -= ctr->blocklen;
ctr->padlen = ctr->blocklen;
continue;
}
#endif
*ct++ = *pt++ ^ ctr->pad[ctr->padlen++];
--len;
}
return CRYPT_OK;
}
#endif
/* $Source$ */
/* $Revision$ */
/* $Date$ */
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