--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/eax_init.c	Mon May 31 18:21:40 2004 +0000
@@ -0,0 +1,106 @@
+/* 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
+ */
+
+/* EAX Implementation by Tom St Denis */
+#include "mycrypt.h"
+
+#ifdef EAX_MODE
+
+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[MAXBLOCKSIZE];
+   int           err, blklen;
+   omac_state    omac;
+   unsigned long len;
+
+
+   _ARGCHK(eax   != NULL);
+   _ARGCHK(key   != NULL);
+   _ARGCHK(nonce != NULL);
+   if (headerlen > 0) {
+      _ARGCHK(header != NULL);
+   }
+
+   if ((err = cipher_is_valid(cipher)) != CRYPT_OK) {
+      return err;
+   }
+   blklen = cipher_descriptor[cipher].block_length;
+
+   /* N = OMAC_0K(nonce) */
+   zeromem(buf, sizeof(buf));
+   if ((err = omac_init(&omac, cipher, key, keylen)) != CRYPT_OK) {
+      return err;
+   }
+
+   /* omac the [0]_n */
+   if ((err = omac_process(&omac, buf, blklen)) != CRYPT_OK) {
+      return err;
+   }
+   /* omac the nonce */
+   if ((err = omac_process(&omac, nonce, noncelen)) != CRYPT_OK) {
+      return err;
+   }
+   /* store result */
+   len = sizeof(eax->N);
+   if ((err = omac_done(&omac, eax->N, &len)) != CRYPT_OK) {
+      return err;
+   }
+
+   /* H = OMAC_1K(header) */
+   zeromem(buf, sizeof(buf));
+   buf[blklen - 1] = 1;
+
+   if ((err = omac_init(&eax->headeromac, cipher, key, keylen)) != CRYPT_OK) {
+      return err;
+   }
+
+   /* omac the [1]_n */
+   if ((err = omac_process(&eax->headeromac, buf, blklen)) != CRYPT_OK) {
+      return err;
+   }
+   /* omac the header */
+   if (headerlen != 0) {
+      if ((err = omac_process(&eax->headeromac, header, headerlen)) != CRYPT_OK) {
+         return 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, &eax->ctr)) != CRYPT_OK) {
+      return err;
+   }
+   /* use big-endian counter */
+   eax->ctr.mode = 1;
+
+   /* setup the OMAC for the ciphertext */
+   if ((err = omac_init(&eax->ctomac, cipher, key, keylen)) != CRYPT_OK) { 
+      return err;
+   }
+
+   /* omac [2]_n */
+   zeromem(buf, sizeof(buf));
+   buf[blklen-1] = 2;
+   if ((err = omac_process(&eax->ctomac, buf, blklen)) != CRYPT_OK) {
+      return err;
+   }
+
+#ifdef CLEAN_STACK
+   zeromem(buf, sizeof(buf));
+   zeromem(&omac, sizeof(omac));
+#endif
+   return CRYPT_OK;
+}
+
+#endif