Mercurial > dropbear
view libtomcrypt/src/modes/ctr/ctr_encrypt.c @ 536:1037aabf701b
- Turn DROPBEAR_SMALL_CODE off by default
author | Matt Johnston <matt@ucc.asn.au> |
---|---|
date | Tue, 03 Mar 2009 13:42:54 +0000 (2009-03-03) |
parents | 0cbe8f6dbf9e |
children | f849a5ca2efc |
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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@gmail.com, http://libtomcrypt.com */ #include "tomcrypt.h" /** @file ctr_encrypt.c CTR implementation, encrypt data, Tom St Denis */ #ifdef LTC_CTR_MODE /** CTR encrypt @param pt Plaintext @param ct [out] Ciphertext @param len Length of plaintext (octets) @param ctr CTR state @return CRYPT_OK if successful */ int ctr_encrypt(const unsigned char *pt, unsigned char *ct, unsigned long len, symmetric_CTR *ctr) { int x, err; LTC_ARGCHK(pt != NULL); LTC_ARGCHK(ct != NULL); LTC_ARGCHK(ctr != NULL); if ((err = cipher_is_valid(ctr->cipher)) != CRYPT_OK) { return err; } /* is blocklen/padlen valid? */ if (ctr->blocklen < 1 || ctr->blocklen > (int)sizeof(ctr->ctr) || ctr->padlen < 0 || ctr->padlen > (int)sizeof(ctr->pad)) { return CRYPT_INVALID_ARG; } #ifdef LTC_FAST if (ctr->blocklen % sizeof(LTC_FAST_TYPE)) { return CRYPT_INVALID_ARG; } #endif /* handle acceleration only if pad is empty, accelerator is present and length is >= a block size */ if ((ctr->padlen == ctr->blocklen) && cipher_descriptor[ctr->cipher].accel_ctr_encrypt != NULL && (len >= (unsigned long)ctr->blocklen)) { if ((err = cipher_descriptor[ctr->cipher].accel_ctr_encrypt(pt, ct, len/ctr->blocklen, ctr->ctr, ctr->mode, &ctr->key)) != CRYPT_OK) { return err; } len %= ctr->blocklen; } while (len) { /* is the pad empty? */ if (ctr->padlen == ctr->blocklen) { /* increment counter */ if (ctr->mode == CTR_COUNTER_LITTLE_ENDIAN) { /* 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 */ if ((err = cipher_descriptor[ctr->cipher].ecb_encrypt(ctr->ctr, ctr->pad, &ctr->key)) != CRYPT_OK) { return err; } ctr->padlen = 0; } #ifdef LTC_FAST if (ctr->padlen == 0 && len >= (unsigned long)ctr->blocklen) { for (x = 0; x < ctr->blocklen; x += sizeof(LTC_FAST_TYPE)) { *((LTC_FAST_TYPE*)((unsigned char *)ct + x)) = *((LTC_FAST_TYPE*)((unsigned char *)pt + x)) ^ *((LTC_FAST_TYPE*)((unsigned char *)ctr->pad + x)); } pt += ctr->blocklen; ct += ctr->blocklen; len -= ctr->blocklen; ctr->padlen = ctr->blocklen; continue; } #endif *ct++ = *pt++ ^ ctr->pad[ctr->padlen++]; --len; } return CRYPT_OK; } #endif /* $Source: /cvs/libtom/libtomcrypt/src/modes/ctr/ctr_encrypt.c,v $ */ /* $Revision: 1.20 $ */ /* $Date: 2006/11/21 00:18:23 $ */