Mercurial > dropbear
view libtomcrypt/src/modes/ctr/ctr_start.c @ 641:2b1bb792cd4d dropbear-tfm
- Update tfm changes to current default tip
author | Matt Johnston <matt@ucc.asn.au> |
---|---|
date | Mon, 21 Nov 2011 19:52:28 +0800 |
parents | 0cbe8f6dbf9e |
children | f849a5ca2efc |
line wrap: on
line source
/* 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, [email protected], http://libtomcrypt.com */ #include "tomcrypt.h" /** @file ctr_start.c CTR implementation, start chain, Tom St Denis */ #ifdef LTC_CTR_MODE /** Initialize a CTR context @param cipher The index of the cipher desired @param IV The initial vector @param key The secret key @param keylen The length of the secret key (octets) @param num_rounds Number of rounds in the cipher desired (0 for default) @param ctr_mode The counter mode (CTR_COUNTER_LITTLE_ENDIAN or CTR_COUNTER_BIG_ENDIAN) @param ctr The CTR state to initialize @return CRYPT_OK if successful */ int ctr_start( int cipher, const unsigned char *IV, const unsigned char *key, int keylen, int num_rounds, int ctr_mode, symmetric_CTR *ctr) { int x, err; LTC_ARGCHK(IV != NULL); LTC_ARGCHK(key != NULL); LTC_ARGCHK(ctr != NULL); /* bad param? */ if ((err = cipher_is_valid(cipher)) != CRYPT_OK) { return err; } /* setup cipher */ if ((err = cipher_descriptor[cipher].setup(key, keylen, num_rounds, &ctr->key)) != CRYPT_OK) { return err; } /* copy ctr */ ctr->blocklen = cipher_descriptor[cipher].block_length; ctr->cipher = cipher; ctr->padlen = 0; ctr->mode = ctr_mode & 1; for (x = 0; x < ctr->blocklen; x++) { ctr->ctr[x] = IV[x]; } if (ctr_mode & LTC_CTR_RFC3686) { /* increment the IV as per RFC 3686 */ 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; } } } } return cipher_descriptor[ctr->cipher].ecb_encrypt(ctr->ctr, ctr->pad, &ctr->key); } #endif /* $Source: /cvs/libtom/libtomcrypt/src/modes/ctr/ctr_start.c,v $ */ /* $Revision: 1.11 $ */ /* $Date: 2006/11/05 01:46:35 $ */