78 lines
1.8 KiB
C
78 lines
1.8 KiB
C
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#include "mycrypt.h"
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#ifdef CTR
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int ctr_start(int cipher, const unsigned char *count, const unsigned char *key, int keylen,
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int num_rounds, symmetric_CTR *ctr)
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{
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int x, errno;
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_ARGCHK(count != NULL);
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_ARGCHK(key != NULL);
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_ARGCHK(ctr != NULL);
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/* bad param? */
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if ((errno = cipher_is_valid(cipher)) != CRYPT_OK) {
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return errno;
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}
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/* setup cipher */
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if ((errno = cipher_descriptor[cipher].setup(key, keylen, num_rounds, &ctr->key)) != CRYPT_OK) {
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return errno;
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}
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/* copy ctr */
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ctr->blocklen = cipher_descriptor[cipher].block_length;
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ctr->cipher = cipher;
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ctr->padlen = 0;
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for (x = 0; x < ctr->blocklen; x++) {
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ctr->ctr[x] = count[x];
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}
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cipher_descriptor[ctr->cipher].ecb_encrypt(ctr->ctr, ctr->pad, &ctr->key);
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return CRYPT_OK;
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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, errno;
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_ARGCHK(pt != NULL);
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_ARGCHK(ct != NULL);
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_ARGCHK(ctr != NULL);
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if ((errno = cipher_is_valid(ctr->cipher)) != CRYPT_OK) {
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return errno;
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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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for (x = 0; x < ctr->blocklen; x++) {
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ctr->ctr[x] = (ctr->ctr[x] + 1) & 255;
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if (ctr->ctr[x] != 0) {
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break;
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}
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}
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/* encrypt it */
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cipher_descriptor[ctr->cipher].ecb_encrypt(ctr->ctr, ctr->pad, &ctr->key);
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ctr->padlen = 0;
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}
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*ct++ = *pt++ ^ ctr->pad[ctr->padlen++];
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}
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return CRYPT_OK;
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}
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int ctr_decrypt(const unsigned char *ct, unsigned char *pt, unsigned long len, symmetric_CTR *ctr)
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{
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_ARGCHK(pt != NULL);
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_ARGCHK(ct != NULL);
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_ARGCHK(ctr != NULL);
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return ctr_encrypt(ct, pt, len, ctr);
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}
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#endif
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