?? ctr_encrypt.c
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/* LibTomCrypt, modular cryptographic library -- Tom St Denis * * LibTomCrypt is a library that provides various cryptographic * algorithms in a highly modular and flexible manner. * * The library is free for all purposes without any express * guarantee it works. * * Tom St Denis, tomstdenis@iahu.ca, http://libtomcrypt.org */#include "mycrypt.h"#ifdef CTRint ctr_encrypt(const unsigned char *pt, unsigned char *ct, unsigned long len, symmetric_CTR *ctr){ int x, err; _ARGCHK(pt != NULL); _ARGCHK(ct != NULL); _ARGCHK(ctr != NULL); if ((err = cipher_is_valid(ctr->cipher)) != CRYPT_OK) { return err; } /* is blocklen/padlen valid? */ if (ctr->blocklen < 0 || ctr->blocklen > (int)sizeof(ctr->ctr) || ctr->padlen < 0 || ctr->padlen > (int)sizeof(ctr->pad)) { return CRYPT_INVALID_ARG; } while (len-- > 0) { /* is the pad empty? */ if (ctr->padlen == ctr->blocklen) { /* increment counter */ if (ctr->mode == 0) { /* little-endian */ for (x = 0; x < ctr->blocklen; x++) { ctr->ctr[x] = (ctr->ctr[x] + (unsigned char)1) & (unsigned char)255; if (ctr->ctr[x] != (unsigned char)0) { break; } } } else { /* big-endian */ for (x = ctr->blocklen-1; x >= 0; x--) { ctr->ctr[x] = (ctr->ctr[x] + (unsigned char)1) & (unsigned char)255; if (ctr->ctr[x] != (unsigned char)0) { break; } } } /* encrypt it */ cipher_descriptor[ctr->cipher].ecb_encrypt(ctr->ctr, ctr->pad, &ctr->key); ctr->padlen = 0; } *ct++ = *pt++ ^ ctr->pad[ctr->padlen++]; } return CRYPT_OK;}#endif
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