--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/omac_init.c	Mon May 31 18:25:41 2004 +0000
@@ -0,0 +1,76 @@
+/* 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
+ */
+/* OMAC1 Support by Tom St Denis (for 64 and 128 bit block ciphers only) */
+#include "mycrypt.h"
+
+#ifdef OMAC
+
+int omac_init(omac_state *omac, int cipher, const unsigned char *key, unsigned long keylen)
+{
+   int err, x, y, mask, msb, len;
+
+   _ARGCHK(omac != NULL);
+   _ARGCHK(key  != NULL);
+
+   /* schedule the key */
+   if ((err = cipher_is_valid(cipher)) != CRYPT_OK) {
+      return err;
+   }
+
+   /* now setup the system */
+   switch (cipher_descriptor[cipher].block_length) {
+       case 8:  mask = 0x1B;
+                len  = 8;
+                break;
+       case 16: mask = 0x87;
+                len  = 16;
+                break;
+       default: return CRYPT_INVALID_ARG;
+   }
+
+   if ((err = cipher_descriptor[cipher].setup(key, keylen, 0, &omac->key)) != CRYPT_OK) {
+      return err;
+   }
+
+   /* ok now we need Lu and Lu^2 [calc one from the other] */
+
+   /* first calc L which is Ek(0) */
+   zeromem(omac->Lu[0], cipher_descriptor[cipher].block_length);
+   cipher_descriptor[cipher].ecb_encrypt(omac->Lu[0], omac->Lu[0], &omac->key);
+
+   /* now do the mults, whoopy! */
+   for (x = 0; x < 2; x++) {
+       /* if msb(L * u^(x+1)) = 0 then just shift, otherwise shift and xor constant mask */
+       msb = omac->Lu[x][0] >> 7;
+
+       /* shift left */
+       for (y = 0; y < (len - 1); y++) {
+           omac->Lu[x][y] = ((omac->Lu[x][y] << 1) | (omac->Lu[x][y+1] >> 7)) & 255;
+       }
+       omac->Lu[x][len - 1] = ((omac->Lu[x][len - 1] << 1) ^ (msb ? mask : 0)) & 255;
+ 
+       /* copy up as require */
+       if (x == 0) {
+          memcpy(omac->Lu[1], omac->Lu[0], sizeof(omac->Lu[0]));
+       }
+   }
+
+   /* setup state */
+   omac->cipher_idx = cipher;
+   omac->buflen     = 0;
+   omac->blklen     = len;
+   zeromem(omac->prev,  sizeof(omac->prev));
+   zeromem(omac->block, sizeof(omac->block));
+
+   return CRYPT_OK;
+}
+
+#endif