--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/modes/lrw/lrw_start.c	Thu Jan 11 02:22:00 2007 +0000
@@ -0,0 +1,103 @@
+/* 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.com
+ */
+#include "tomcrypt.h"
+
+/**
+   @file lrw_start.c
+   LRW_MODE implementation, start mode, Tom St Denis
+*/
+
+#ifdef LTC_LRW_MODE
+
+/**
+  Initialize the LRW context
+  @param cipher        The cipher desired, must be a 128-bit block cipher 
+  @param IV            The index value, must be 128-bits
+  @param key           The cipher key 
+  @param keylen        The length of the cipher key in octets
+  @param tweak         The tweak value (second key), must be 128-bits
+  @param num_rounds    The number of rounds for the cipher (0 == default)
+  @param lrw           [out] The LRW state
+  @return CRYPT_OK on success.
+*/
+int lrw_start(               int   cipher,
+              const unsigned char *IV,
+              const unsigned char *key,       int keylen,
+              const unsigned char *tweak,
+                             int  num_rounds, 
+                   symmetric_LRW *lrw)
+{
+   int           err;
+#ifdef LRW_TABLES
+   unsigned char B[16];
+   int           x, y, z, t;
+#endif
+
+  LTC_ARGCHK(IV    != NULL);
+  LTC_ARGCHK(key   != NULL);
+  LTC_ARGCHK(tweak != NULL);
+  LTC_ARGCHK(lrw   != NULL);
+
+#ifdef LTC_FAST
+   if (16 % sizeof(LTC_FAST_TYPE)) {
+      return CRYPT_INVALID_ARG;
+   }
+#endif
+
+   /* is cipher valid? */
+   if ((err = cipher_is_valid(cipher)) != CRYPT_OK) {
+      return err;
+   }
+   if (cipher_descriptor[cipher].block_length != 16) {
+      return CRYPT_INVALID_CIPHER;
+   }
+
+   /* schedule key */
+   if ((err = cipher_descriptor[cipher].setup(key, keylen, num_rounds, &lrw->key)) != CRYPT_OK) {
+      return err;
+   }
+   lrw->cipher = cipher;
+
+   /* copy the IV and tweak */
+   XMEMCPY(lrw->tweak, tweak, 16);
+
+#ifdef LRW_TABLES
+   /* setup tables */
+   /* generate the first table as it has no shifting (from which we make the other tables) */
+   zeromem(B, 16);
+   for (y = 0; y < 256; y++) {
+        B[0] = y;
+        gcm_gf_mult(tweak, B, &lrw->PC[0][y][0]);
+   }
+
+   /* now generate the rest of the tables based the previous table */
+   for (x = 1; x < 16; x++) {
+      for (y = 0; y < 256; y++) {
+         /* now shift it right by 8 bits */
+         t = lrw->PC[x-1][y][15];
+         for (z = 15; z > 0; z--) {
+             lrw->PC[x][y][z] = lrw->PC[x-1][y][z-1];
+         }
+         lrw->PC[x][y][0]  = gcm_shift_table[t<<1];
+         lrw->PC[x][y][1] ^= gcm_shift_table[(t<<1)+1];
+     }
+  }
+#endif
+
+   /* generate first pad */
+   return lrw_setiv(IV, 16, lrw);
+}
+
+
+#endif
+/* $Source: /cvs/libtom/libtomcrypt/src/modes/lrw/lrw_start.c,v $ */
+/* $Revision: 1.11 $ */
+/* $Date: 2006/06/29 01:53:13 $ */