--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtomcrypt/src/encauth/gcm/gcm_add_aad.c	Wed Mar 08 13:23:58 2006 +0000
@@ -0,0 +1,124 @@
+/* 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_aad.c
+   GCM implementation, Add AAD data to the stream, by Tom St Denis
+*/
+#include "tomcrypt.h"
+
+#ifdef GCM_MODE
+
+/**
+  Add AAD to the GCM state
+  @param gcm       The GCM state
+  @param adata     The additional authentication data to add to the GCM state
+  @param adatalen  The length of the AAD data.
+  @return CRYPT_OK on success
+ */
+int gcm_add_aad(gcm_state *gcm,
+               const unsigned char *adata,  unsigned long adatalen)
+{
+   unsigned long x;
+   int           err;
+#ifdef LTC_FAST
+   unsigned long y;
+#endif
+
+   LTC_ARGCHK(gcm    != NULL);
+   if (adatalen > 0) {
+      LTC_ARGCHK(adata  != NULL);
+   }
+
+   if (gcm->buflen > 16 || gcm->buflen < 0) {
+      return CRYPT_INVALID_ARG;
+   }
+
+   if ((err = cipher_is_valid(gcm->cipher)) != CRYPT_OK) {
+      return err;
+   }
+
+   /* in IV mode? */
+   if (gcm->mode == GCM_MODE_IV) {
+      /* let's process the IV */
+      if (gcm->ivmode || gcm->buflen != 12) {
+         for (x = 0; x < (unsigned long)gcm->buflen; x++) {
+             gcm->X[x] ^= gcm->buf[x];
+         }
+         if (gcm->buflen) {
+            gcm->totlen += gcm->buflen * CONST64(8);
+            gcm_mult_h(gcm, gcm->X);
+         }
+ 
+         /* mix in the length */
+         zeromem(gcm->buf, 8);
+         STORE64H(gcm->totlen, gcm->buf+8);
+         for (x = 0; x < 16; x++) {
+             gcm->X[x] ^= gcm->buf[x];
+         }
+         gcm_mult_h(gcm, gcm->X);
+
+         /* copy counter out */ 
+         XMEMCPY(gcm->Y, gcm->X, 16);
+         zeromem(gcm->X, 16);
+      } else {
+         XMEMCPY(gcm->Y, gcm->buf, 12);
+         gcm->Y[12] = 0;
+         gcm->Y[13] = 0;
+         gcm->Y[14] = 0;
+         gcm->Y[15] = 1;
+      }
+      XMEMCPY(gcm->Y_0, gcm->Y, 16);
+      zeromem(gcm->buf, 16);
+      gcm->buflen = 0;
+      gcm->totlen = 0;
+      gcm->mode   = GCM_MODE_AAD;
+   }
+
+   if (gcm->mode != GCM_MODE_AAD || gcm->buflen >= 16) {
+      return CRYPT_INVALID_ARG;
+   }
+
+   x = 0;
+#ifdef LTC_FAST
+   if (gcm->buflen == 0) {
+      for (x = 0; x < (adatalen & ~15); x += 16) {
+          for (y = 0; y < 16; y += sizeof(LTC_FAST_TYPE)) {
+              *((LTC_FAST_TYPE*)(&gcm->X[y])) ^= *((LTC_FAST_TYPE*)(&adata[x + y]));
+          }
+          gcm_mult_h(gcm, gcm->X);
+          gcm->totlen += 128;
+      }
+      adata += x;
+   }
+#endif
+
+
+   /* start adding AAD data to the state */
+   for (; x < adatalen; x++) {
+       gcm->X[gcm->buflen++] ^= *adata++;
+
+       if (gcm->buflen == 16) {
+         /* GF mult it */
+         gcm_mult_h(gcm, gcm->X);
+         gcm->buflen = 0;
+         gcm->totlen += 128;
+      }
+   }
+
+   return CRYPT_OK;
+}
+#endif
+   
+
+/* $Source: /cvs/libtom/libtomcrypt/src/encauth/gcm/gcm_add_aad.c,v $ */
+/* $Revision: 1.14 $ */
+/* $Date: 2005/05/05 14:35:58 $ */