68 lines
1.6 KiB
C
68 lines
1.6 KiB
C
#include "mycrypt.h"
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#ifdef OFB
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int ofb_start(int cipher, const unsigned char *IV, const unsigned char *key,
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int keylen, int num_rounds, symmetric_OFB *ofb)
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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(ofb != 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 details */
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ofb->cipher = cipher;
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ofb->blocklen = cipher_descriptor[cipher].block_length;
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for (x = 0; x < ofb->blocklen; x++) {
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ofb->IV[x] = IV[x];
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}
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/* init the cipher */
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ofb->padlen = ofb->blocklen;
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return cipher_descriptor[cipher].setup(key, keylen, num_rounds, &ofb->key);
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}
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int ofb_encrypt(const unsigned char *pt, unsigned char *ct, unsigned long len, symmetric_OFB *ofb)
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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(ofb != NULL);
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if ((err = cipher_is_valid(ofb->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 (ofb->blocklen < 0 || ofb->blocklen > (int)sizeof(ofb->IV) ||
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ofb->padlen < 0 || ofb->padlen > (int)sizeof(ofb->IV)) {
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return CRYPT_INVALID_ARG;
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}
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while (len-- > 0) {
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if (ofb->padlen == ofb->blocklen) {
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cipher_descriptor[ofb->cipher].ecb_encrypt(ofb->IV, ofb->IV, &ofb->key);
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ofb->padlen = 0;
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}
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*ct++ = *pt++ ^ ofb->IV[ofb->padlen++];
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}
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return CRYPT_OK;
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}
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int ofb_decrypt(const unsigned char *ct, unsigned char *pt, unsigned long len, symmetric_OFB *ofb)
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{
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_ARGCHK(pt != NULL);
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_ARGCHK(ct != NULL);
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_ARGCHK(ofb != NULL);
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return ofb_encrypt(ct, pt, len, ofb);
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}
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#endif
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