112 lines
2.6 KiB
C
112 lines
2.6 KiB
C
#include "mycrypt.h"
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#ifdef CBC
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int cbc_start(int cipher, const unsigned char *IV, const unsigned char *key,
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int keylen, int num_rounds, symmetric_CBC *cbc)
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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(cbc != NULL);
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/* bad param? */
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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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/* setup cipher */
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if ((err = cipher_descriptor[cipher].setup(key, keylen, num_rounds, &cbc->key)) != CRYPT_OK) {
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return err;
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}
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/* copy IV */
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cbc->blocklen = cipher_descriptor[cipher].block_length;
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cbc->cipher = cipher;
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for (x = 0; x < cbc->blocklen; x++) {
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cbc->IV[x] = IV[x];
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}
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return CRYPT_OK;
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}
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int cbc_encrypt(const unsigned char *pt, unsigned char *ct, symmetric_CBC *cbc)
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{
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int x, err;
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unsigned char tmp[MAXBLOCKSIZE];
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_ARGCHK(pt != NULL);
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_ARGCHK(ct != NULL);
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_ARGCHK(cbc != NULL);
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if ((err = cipher_is_valid(cbc->cipher)) != CRYPT_OK) {
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return err;
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}
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/* is blocklen valid? */
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if (cbc->blocklen < 0 || cbc->blocklen > (int)sizeof(cbc->IV)) {
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return CRYPT_INVALID_ARG;
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}
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/* xor IV against plaintext */
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for (x = 0; x < cbc->blocklen; x++) {
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tmp[x] = pt[x] ^ cbc->IV[x];
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}
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/* encrypt */
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cipher_descriptor[cbc->cipher].ecb_encrypt(tmp, ct, &cbc->key);
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/* store IV [ciphertext] for a future block */
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for (x = 0; x < cbc->blocklen; x++) {
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cbc->IV[x] = ct[x];
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}
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#ifdef CLEAN_STACK
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zeromem(tmp, sizeof(tmp));
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#endif
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return CRYPT_OK;
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}
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int cbc_decrypt(const unsigned char *ct, unsigned char *pt, symmetric_CBC *cbc)
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{
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int x, err;
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unsigned char tmp[MAXBLOCKSIZE], tmp2[MAXBLOCKSIZE];
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_ARGCHK(pt != NULL);
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_ARGCHK(ct != NULL);
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_ARGCHK(cbc != NULL);
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/* decrypt the block from ct into tmp */
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if ((err = cipher_is_valid(cbc->cipher)) != CRYPT_OK) {
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return err;
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}
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cipher_descriptor[cbc->cipher].ecb_decrypt(ct, tmp, &cbc->key);
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/* is blocklen valid? */
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if (cbc->blocklen < 0 || cbc->blocklen > (int)sizeof(cbc->IV)) {
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return CRYPT_INVALID_ARG;
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}
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/* xor IV against the plaintext of the previous step */
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for (x = 0; x < cbc->blocklen; x++) {
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/* copy CT in case ct == pt */
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tmp2[x] = ct[x];
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/* actually decrypt the byte */
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pt[x] = tmp[x] ^ cbc->IV[x];
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}
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/* replace IV with this current ciphertext */
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for (x = 0; x < cbc->blocklen; x++) {
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cbc->IV[x] = tmp2[x];
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}
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#ifdef CLEAN_STACK
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zeromem(tmp, sizeof(tmp));
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zeromem(tmp2, sizeof(tmp2));
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#endif
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return CRYPT_OK;
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}
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#endif
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