--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtomcrypt/src/encauth/eax/eax_init.c	Wed Mar 08 13:23:58 2006 +0000
@@ -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, [email protected], 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 $ */