forked from libtom/libtomcrypt
/
cfb.c
86 lines (70 loc) · 1.99 KB
/
cfb.c
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#include "mycrypt.h"
#ifdef CFB
int cfb_start(int cipher, const unsigned char *IV, const unsigned char *key,
int keylen, int num_rounds, symmetric_CFB *cfb)
{
int x, errno;
_ARGCHK(IV != NULL);
_ARGCHK(key != NULL);
_ARGCHK(cfb != NULL);
if ((errno = cipher_is_valid(cipher)) != CRYPT_OK) {
return errno;
}
/* copy data */
cfb->cipher = cipher;
cfb->blocklen = cipher_descriptor[cipher].block_length;
for (x = 0; x < cfb->blocklen; x++)
cfb->IV[x] = IV[x];
/* init the cipher */
if ((errno = cipher_descriptor[cipher].setup(key, keylen, num_rounds, &cfb->key)) != CRYPT_OK) {
return errno;
}
/* encrypt the IV */
cipher_descriptor[cfb->cipher].ecb_encrypt(cfb->IV, cfb->IV, &cfb->key);
cfb->padlen = 0;
return CRYPT_OK;
}
int cfb_encrypt(const unsigned char *pt, unsigned char *ct, unsigned long len, symmetric_CFB *cfb)
{
int errno;
_ARGCHK(pt != NULL);
_ARGCHK(ct != NULL);
_ARGCHK(cfb != NULL);
if ((errno = cipher_is_valid(cfb->cipher)) != CRYPT_OK) {
return errno;
}
while (len--) {
if (cfb->padlen == cfb->blocklen) {
cipher_descriptor[cfb->cipher].ecb_encrypt(cfb->pad, cfb->IV, &cfb->key);
cfb->padlen = 0;
}
cfb->pad[cfb->padlen] = (*ct = *pt ^ cfb->IV[cfb->padlen]);
++pt;
++ct;
++cfb->padlen;
}
return CRYPT_OK;
}
int cfb_decrypt(const unsigned char *ct, unsigned char *pt, unsigned long len, symmetric_CFB *cfb)
{
int errno;
_ARGCHK(pt != NULL);
_ARGCHK(ct != NULL);
_ARGCHK(cfb != NULL);
if ((errno = cipher_is_valid(cfb->cipher)) != CRYPT_OK) {
return errno;
}
while (len--) {
if (cfb->padlen == cfb->blocklen) {
cipher_descriptor[cfb->cipher].ecb_encrypt(cfb->pad, cfb->IV, &cfb->key);
cfb->padlen = 0;
}
cfb->pad[cfb->padlen] = *ct;
*pt = *ct ^ cfb->IV[cfb->padlen];
++pt;
++ct;
++cfb->padlen;
}
return CRYPT_OK;
}
#endif