/* 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.org *//**    @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: 1.4 $ *//* $Date: 2005/05/05 14:35:58 $ */