1 files changed, 107 insertions, 0 deletions
diff --git a/libtomcrypt/src/encauth/gcm/gcm_init.c b/libtomcrypt/src/encauth/gcm/gcm_init.c
new file mode 100644
index 0000000..c0f7a5a
--- /dev/null
+++ b/libtomcrypt/src/encauth/gcm/gcm_init.c
@@ -0,0 +1,107 @@
+/* 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, tomstdenis@gmail.com, http://libtomcrypt.com
+ */
+
+/**
+   @file gcm_init.c
+   GCM implementation, initialize state, by Tom St Denis
+*/
+#include "tomcrypt.h"
+
+#ifdef GCM_MODE
+
+/**
+  Initialize a GCM state
+  @param gcm     The GCM state to initialize
+  @param cipher  The index of the cipher to use
+  @param key     The secret key
+  @param keylen  The length of the secret key
+  @return CRYPT_OK on success
+ */
+int gcm_init(gcm_state *gcm, int cipher, 
+             const unsigned char *key,  int keylen)
+{
+   int           err;
+   unsigned char B[16];
+#ifdef GCM_TABLES
+   int           x, y, z, t;
+#endif
+
+   LTC_ARGCHK(gcm != NULL);
+   LTC_ARGCHK(key != 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, 0, &gcm->K)) != CRYPT_OK) {
+      return err;
+   }
+
+   /* H = E(0) */
+   zeromem(B, 16);
+   if ((err = cipher_descriptor[cipher].ecb_encrypt(B, gcm->H, &gcm->K)) != CRYPT_OK) {
+      return err;
+   }
+
+   /* setup state */
+   zeromem(gcm->buf, sizeof(gcm->buf));
+   zeromem(gcm->X,   sizeof(gcm->X));
+   gcm->cipher   = cipher;
+   gcm->mode     = GCM_MODE_IV;
+   gcm->ivmode   = 0;
+   gcm->buflen   = 0;
+   gcm->totlen   = 0;
+   gcm->pttotlen = 0;
+
+#ifdef GCM_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(gcm->H, B, &gcm->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 = gcm->PC[x-1][y][15];
+         for (z = 15; z > 0; z--) {
+             gcm->PC[x][y][z] = gcm->PC[x-1][y][z-1];
+         }
+         gcm->PC[x][y][0] = gcm_shift_table[t<<1];
+         gcm->PC[x][y][1] ^= gcm_shift_table[(t<<1)+1];
+     }
+  }
+
+#endif
+
+   return CRYPT_OK;
+}
+
+#endif
+
+/* $Source: /cvs/libtom/libtomcrypt/src/encauth/gcm/gcm_init.c,v $ */
+/* $Revision: 1.18 $ */
+/* $Date: 2006/03/31 14:15:35 $ */