--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/encauth/ocb/ocb_init.c	Wed Mar 08 12:58:00 2006 +0000
@@ -0,0 +1,133 @@
+/* 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 ocb_init.c
+   OCB implementation, initialize state, by Tom St Denis
+*/
+#include "tomcrypt.h"
+
+#ifdef OCB_MODE
+
+static const struct {
+    int           len;
+    unsigned char poly_div[MAXBLOCKSIZE], 
+                  poly_mul[MAXBLOCKSIZE];
+} polys[] = {
+{
+    8,
+    { 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0D },
+    { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x1B }
+}, {
+    16, 
+    { 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x43 },
+    { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x87 }
+}
+};
+
+/**
+  Initialize an OCB context.
+  @param ocb     [out] The destination of the OCB state
+  @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 session nonce (length of the block size of the cipher)
+  @return CRYPT_OK if successful
+*/
+int ocb_init(ocb_state *ocb, int cipher, 
+             const unsigned char *key, unsigned long keylen, const unsigned char *nonce)
+{
+   int poly, x, y, m, err;
+
+   LTC_ARGCHK(ocb   != NULL);
+   LTC_ARGCHK(key   != NULL);
+   LTC_ARGCHK(nonce != NULL);
+
+   /* valid cipher? */
+   if ((err = cipher_is_valid(cipher)) != CRYPT_OK) {
+      return err;
+   }
+
+   /* determine which polys to use */
+   ocb->block_len = cipher_descriptor[cipher].block_length;
+   for (poly = 0; poly < (int)(sizeof(polys)/sizeof(polys[0])); poly++) {
+       if (polys[poly].len == ocb->block_len) { 
+          break;
+       }
+   }
+   if (polys[poly].len != ocb->block_len) {
+      return CRYPT_INVALID_ARG;
+   }   
+
+   /* schedule the key */
+   if ((err = cipher_descriptor[cipher].setup(key, keylen, 0, &ocb->key)) != CRYPT_OK) {
+      return err;
+   }
+ 
+   /* find L = E[0] */
+   zeromem(ocb->L, ocb->block_len);
+   cipher_descriptor[cipher].ecb_encrypt(ocb->L, ocb->L, &ocb->key);
+
+   /* find R = E[N xor L] */
+   for (x = 0; x < ocb->block_len; x++) {
+       ocb->R[x] = ocb->L[x] ^ nonce[x];
+   }
+   cipher_descriptor[cipher].ecb_encrypt(ocb->R, ocb->R, &ocb->key);
+
+   /* find Ls[i] = L << i for i == 0..31 */
+   XMEMCPY(ocb->Ls[0], ocb->L, ocb->block_len);
+   for (x = 1; x < 32; x++) {
+       m = ocb->Ls[x-1][0] >> 7;
+       for (y = 0; y < ocb->block_len-1; y++) {
+           ocb->Ls[x][y] = ((ocb->Ls[x-1][y] << 1) | (ocb->Ls[x-1][y+1] >> 7)) & 255;
+       }
+       ocb->Ls[x][ocb->block_len-1] = (ocb->Ls[x-1][ocb->block_len-1] << 1) & 255;
+
+       if (m == 1) {
+          for (y = 0; y < ocb->block_len; y++) {
+              ocb->Ls[x][y] ^= polys[poly].poly_mul[y];
+          }
+       }
+    }
+
+    /* find Lr = L / x */
+    m = ocb->L[ocb->block_len-1] & 1;
+
+    /* shift right */
+    for (x = ocb->block_len - 1; x > 0; x--) {
+        ocb->Lr[x] = ((ocb->L[x] >> 1) | (ocb->L[x-1] << 7)) & 255;
+    }
+    ocb->Lr[0] = ocb->L[0] >> 1;
+
+    if (m == 1) {
+       for (x = 0; x < ocb->block_len; x++) {
+           ocb->Lr[x] ^= polys[poly].poly_div[x];
+       }
+    }
+
+    /* set Li, checksum */
+    zeromem(ocb->Li,       ocb->block_len);
+    zeromem(ocb->checksum, ocb->block_len);
+
+    /* set other params */
+    ocb->block_index = 1;
+    ocb->cipher      = cipher;
+
+    return CRYPT_OK;
+}
+
+#endif
+
+/* $Source: /cvs/libtom/libtomcrypt/src/encauth/ocb/ocb_init.c,v $ */
+/* $Revision: 1.3 $ */
+/* $Date: 2005/05/05 14:35:58 $ */