--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/encauth/gcm/gcm_add_iv.c	Fri May 06 13:23:02 2005 +0000
@@ -0,0 +1,90 @@
+/* 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 gcm_add_iv.c
+   GCM implementation, add IV data to the state, by Tom St Denis
+*/
+#include "tomcrypt.h"
+
+#ifdef GCM_MODE
+
+/**
+  Add IV data to the GCM state
+  @param gcm    The GCM state
+  @param IV     The initial value data to add
+  @param IVlen  The length of the IV
+  @return CRYPT_OK on success
+ */
+int gcm_add_iv(gcm_state *gcm, 
+               const unsigned char *IV,     unsigned long IVlen)
+{
+   unsigned long x, y;
+   int           err;
+
+   LTC_ARGCHK(gcm != NULL);
+   if (IVlen > 0) {
+      LTC_ARGCHK(IV  != NULL);
+   }
+
+   /* must be in IV mode */
+   if (gcm->mode != GCM_MODE_IV) {
+      return CRYPT_INVALID_ARG;
+   }
+ 
+   if (gcm->buflen >= 16 || gcm->buflen < 0) {
+      return CRYPT_INVALID_ARG;
+   }
+
+   if ((err = cipher_is_valid(gcm->cipher)) != CRYPT_OK) {
+      return err;
+   }
+
+
+   /* trip the ivmode flag */
+   if (IVlen + gcm->buflen > 12) {
+      gcm->ivmode |= 1;
+   }
+
+   x = 0;
+#ifdef LTC_FAST
+   if (gcm->buflen == 0) {
+      for (x = 0; x < (IVlen & ~15); x += 16) {
+          for (y = 0; y < 16; y += sizeof(LTC_FAST_TYPE)) {
+              *((LTC_FAST_TYPE*)(&gcm->X[y])) ^= *((LTC_FAST_TYPE*)(&IV[x + y]));
+          }
+          gcm_mult_h(gcm, gcm->X);
+          gcm->totlen += 128;
+      }
+      IV += x;
+   }
+#endif
+
+   /* start adding IV data to the state */
+   for (; x < IVlen; x++) {
+       gcm->buf[gcm->buflen++] = *IV++;
+
+       if (gcm->buflen == 16) {
+         /* GF mult it */
+         for (y = 0; y < 16; y++) {
+             gcm->X[y] ^= gcm->buf[y];
+         }
+         gcm_mult_h(gcm, gcm->X);
+         gcm->buflen = 0;
+         gcm->totlen += 128;
+      }
+   }
+
+   return CRYPT_OK;
+}
+
+#endif
+