112 lines
2.7 KiB
C
112 lines
2.7 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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* gurantee it works.
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*
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* Tom St Denis, tomstdenis@iahu.ca, http://libtomcrypt.org
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*/
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#include "mycrypt.h"
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#ifdef CFB
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int cfb_start(int cipher, const unsigned char *IV, const unsigned char *key,
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int keylen, int num_rounds, symmetric_CFB *cfb)
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{
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int x, err;
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_ARGCHK(IV != NULL);
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_ARGCHK(key != NULL);
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_ARGCHK(cfb != NULL);
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if ((err = cipher_is_valid(cipher)) != CRYPT_OK) {
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return err;
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}
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/* copy data */
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cfb->cipher = cipher;
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cfb->blocklen = cipher_descriptor[cipher].block_length;
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for (x = 0; x < cfb->blocklen; x++)
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cfb->IV[x] = IV[x];
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/* init the cipher */
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if ((err = cipher_descriptor[cipher].setup(key, keylen, num_rounds, &cfb->key)) != CRYPT_OK) {
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return err;
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}
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/* encrypt the IV */
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cipher_descriptor[cfb->cipher].ecb_encrypt(cfb->IV, cfb->IV, &cfb->key);
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cfb->padlen = 0;
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return CRYPT_OK;
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}
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int cfb_encrypt(const unsigned char *pt, unsigned char *ct, unsigned long len, symmetric_CFB *cfb)
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{
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int err;
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_ARGCHK(pt != NULL);
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_ARGCHK(ct != NULL);
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_ARGCHK(cfb != NULL);
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if ((err = cipher_is_valid(cfb->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 (cfb->blocklen < 0 || cfb->blocklen > (int)sizeof(cfb->IV) ||
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cfb->padlen < 0 || cfb->padlen > (int)sizeof(cfb->pad)) {
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return CRYPT_INVALID_ARG;
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}
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while (len-- > 0) {
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if (cfb->padlen == cfb->blocklen) {
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cipher_descriptor[cfb->cipher].ecb_encrypt(cfb->pad, cfb->IV, &cfb->key);
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cfb->padlen = 0;
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}
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cfb->pad[cfb->padlen] = (*ct = *pt ^ cfb->IV[cfb->padlen]);
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++pt;
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++ct;
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++cfb->padlen;
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}
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return CRYPT_OK;
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}
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int cfb_decrypt(const unsigned char *ct, unsigned char *pt, unsigned long len, symmetric_CFB *cfb)
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{
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int err;
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_ARGCHK(pt != NULL);
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_ARGCHK(ct != NULL);
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_ARGCHK(cfb != NULL);
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if ((err = cipher_is_valid(cfb->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 (cfb->blocklen < 0 || cfb->blocklen > (int)sizeof(cfb->IV) ||
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cfb->padlen < 0 || cfb->padlen > (int)sizeof(cfb->pad)) {
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return CRYPT_INVALID_ARG;
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}
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while (len-- > 0) {
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if (cfb->padlen == cfb->blocklen) {
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cipher_descriptor[cfb->cipher].ecb_encrypt(cfb->pad, cfb->IV, &cfb->key);
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cfb->padlen = 0;
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}
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cfb->pad[cfb->padlen] = *ct;
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*pt = *ct ^ cfb->IV[cfb->padlen];
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++pt;
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++ct;
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++cfb->padlen;
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}
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return CRYPT_OK;
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}
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#endif
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