diff options
Diffstat (limited to 'libtomcrypt/src/encauth/eax/eax_init.c')
| -rw-r--r-- | libtomcrypt/src/encauth/eax/eax_init.c | 144 |
1 files changed, 144 insertions, 0 deletions
diff --git a/libtomcrypt/src/encauth/eax/eax_init.c b/libtomcrypt/src/encauth/eax/eax_init.c new file mode 100644 index 0000000..48512b5 --- /dev/null +++ b/libtomcrypt/src/encauth/eax/eax_init.c @@ -0,0 +1,144 @@ +/* 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 + */ + +/** + @file eax_init.c + EAX implementation, initialized EAX state, by Tom St Denis +*/ +#include "tomcrypt.h" + +#ifdef EAX_MODE + +/** + Initialized an EAX state + @param eax [out] The EAX state to initialize + @param cipher The index of the desired cipher + @param key The secret key + @param keylen The length of the secret key (octets) + @param nonce The use-once nonce for the session + @param noncelen The length of the nonce (octets) + @param header The header for the EAX state + @param headerlen The header length (octets) + @return CRYPT_OK if successful +*/ +int eax_init(eax_state *eax, int cipher, + const unsigned char *key, unsigned long keylen, + const unsigned char *nonce, unsigned long noncelen, + const unsigned char *header, unsigned long headerlen) +{ + unsigned char *buf; + int err, blklen; + omac_state *omac; + unsigned long len; + + + LTC_ARGCHK(eax != NULL); + LTC_ARGCHK(key != NULL); + LTC_ARGCHK(nonce != NULL); + if (headerlen > 0) { + LTC_ARGCHK(header != NULL); + } + + if ((err = cipher_is_valid(cipher)) != CRYPT_OK) { + return err; + } + blklen = cipher_descriptor[cipher].block_length; + + /* allocate ram */ + buf = XMALLOC(MAXBLOCKSIZE); + omac = XMALLOC(sizeof(*omac)); + + if (buf == NULL || omac == NULL) { + if (buf != NULL) { + XFREE(buf); + } + if (omac != NULL) { + XFREE(omac); + } + return CRYPT_MEM; + } + + /* N = OMAC_0K(nonce) */ + zeromem(buf, MAXBLOCKSIZE); + if ((err = omac_init(omac, cipher, key, keylen)) != CRYPT_OK) { + goto LBL_ERR; + } + + /* omac the [0]_n */ + if ((err = omac_process(omac, buf, blklen)) != CRYPT_OK) { + goto LBL_ERR; + } + /* omac the nonce */ + if ((err = omac_process(omac, nonce, noncelen)) != CRYPT_OK) { + goto LBL_ERR; + } + /* store result */ + len = sizeof(eax->N); + if ((err = omac_done(omac, eax->N, &len)) != CRYPT_OK) { + goto LBL_ERR; + } + + /* H = OMAC_1K(header) */ + zeromem(buf, MAXBLOCKSIZE); + buf[blklen - 1] = 1; + + if ((err = omac_init(&eax->headeromac, cipher, key, keylen)) != CRYPT_OK) { + goto LBL_ERR; + } + + /* omac the [1]_n */ + if ((err = omac_process(&eax->headeromac, buf, blklen)) != CRYPT_OK) { + goto LBL_ERR; + } + /* omac the header */ + if (headerlen != 0) { + if ((err = omac_process(&eax->headeromac, header, headerlen)) != CRYPT_OK) { + goto LBL_ERR; + } + } + + /* note we don't finish the headeromac, this allows us to add more header later */ + + /* setup the CTR mode */ + if ((err = ctr_start(cipher, eax->N, key, keylen, 0, CTR_COUNTER_BIG_ENDIAN, &eax->ctr)) != CRYPT_OK) { + goto LBL_ERR; + } + + /* setup the OMAC for the ciphertext */ + if ((err = omac_init(&eax->ctomac, cipher, key, keylen)) != CRYPT_OK) { + goto LBL_ERR; + } + + /* omac [2]_n */ + zeromem(buf, MAXBLOCKSIZE); + buf[blklen-1] = 2; + if ((err = omac_process(&eax->ctomac, buf, blklen)) != CRYPT_OK) { + goto LBL_ERR; + } + + err = CRYPT_OK; +LBL_ERR: +#ifdef LTC_CLEAN_STACK + zeromem(buf, MAXBLOCKSIZE); + zeromem(omac, sizeof(*omac)); +#endif + + XFREE(omac); + XFREE(buf); + + return err; +} + +#endif + +/* $Source: /cvs/libtom/libtomcrypt/src/encauth/eax/eax_init.c,v $ */ +/* $Revision: 1.5 $ */ +/* $Date: 2006/03/31 14:15:35 $ */ |