Tom St Denis
113 lines
3.3 KiB
C
113 lines
3.3 KiB
C
/* LibTomCrypt, modular cryptographic library -- Tom St Denis
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*
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* LibTomCrypt is a library that provides various cryptographic
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* algorithms in a highly modular and flexible manner.
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*
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* The library is free for all purposes without any express
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* guarantee it works.
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*
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* Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.com
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*/
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#include "tomcrypt.h"
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/**
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@file ctr_encrypt.c
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CTR implementation, encrypt data, Tom St Denis
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*/
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#ifdef LTC_CTR_MODE
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/**
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CTR encrypt
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@param pt Plaintext
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@param ct [out] Ciphertext
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@param len Length of plaintext (octets)
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@param ctr CTR state
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@return CRYPT_OK if successful
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*/
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int ctr_encrypt(const unsigned char *pt, unsigned char *ct, unsigned long len, symmetric_CTR *ctr)
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{
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int x, err;
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LTC_ARGCHK(pt != NULL);
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LTC_ARGCHK(ct != NULL);
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LTC_ARGCHK(ctr != NULL);
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if ((err = cipher_is_valid(ctr->cipher)) != CRYPT_OK) {
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return err;
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}
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/* is blocklen/padlen valid? */
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if (ctr->blocklen < 1 || ctr->blocklen > (int)sizeof(ctr->ctr) ||
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ctr->padlen < 0 || ctr->padlen > (int)sizeof(ctr->pad)) {
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return CRYPT_INVALID_ARG;
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}
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#ifdef LTC_FAST
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if (ctr->blocklen % sizeof(LTC_FAST_TYPE)) {
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return CRYPT_INVALID_ARG;
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}
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#endif
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/* handle acceleration only if pad is empty, accelerator is present and length is >= a block size */
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if ((ctr->padlen == ctr->blocklen) && cipher_descriptor[ctr->cipher].accel_ctr_encrypt != NULL && (len >= (unsigned long)ctr->blocklen)) {
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if ((err = cipher_descriptor[ctr->cipher].accel_ctr_encrypt(pt, ct, len/ctr->blocklen, ctr->ctr, ctr->mode, &ctr->key)) != CRYPT_OK) {
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return err;
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}
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len %= ctr->blocklen;
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}
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while (len) {
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/* is the pad empty? */
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if (ctr->padlen == ctr->blocklen) {
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/* increment counter */
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if (ctr->mode == CTR_COUNTER_LITTLE_ENDIAN) {
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/* little-endian */
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for (x = 0; x < ctr->blocklen; x++) {
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ctr->ctr[x] = (ctr->ctr[x] + (unsigned char)1) & (unsigned char)255;
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if (ctr->ctr[x] != (unsigned char)0) {
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break;
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}
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}
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} else {
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/* big-endian */
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for (x = ctr->blocklen-1; x >= 0; x--) {
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ctr->ctr[x] = (ctr->ctr[x] + (unsigned char)1) & (unsigned char)255;
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if (ctr->ctr[x] != (unsigned char)0) {
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break;
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}
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}
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}
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/* encrypt it */
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if ((err = cipher_descriptor[ctr->cipher].ecb_encrypt(ctr->ctr, ctr->pad, &ctr->key)) != CRYPT_OK) {
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return err;
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}
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ctr->padlen = 0;
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}
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#ifdef LTC_FAST
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if (ctr->padlen == 0 && len >= (unsigned long)ctr->blocklen) {
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for (x = 0; x < ctr->blocklen; x += sizeof(LTC_FAST_TYPE)) {
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*((LTC_FAST_TYPE*)((unsigned char *)ct + x)) = *((LTC_FAST_TYPE*)((unsigned char *)pt + x)) ^
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*((LTC_FAST_TYPE*)((unsigned char *)ctr->pad + x));
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}
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pt += ctr->blocklen;
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ct += ctr->blocklen;
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len -= ctr->blocklen;
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ctr->padlen = ctr->blocklen;
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continue;
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}
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#endif
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*ct++ = *pt++ ^ ctr->pad[ctr->padlen++];
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--len;
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}
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return CRYPT_OK;
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}
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#endif
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/* $Source$ */
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/* $Revision$ */
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/* $Date$ */
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