Add current version of libSRTP from CVS.

libsrtp/crypto/math/gf2_8.c

+/*
+ * gf2_8.c
+ *
+ * GF(256) finite field implementation, with the representation used
+ * in the AES cipher.
+ * 
+ * David A. McGrew
+ * Cisco Systems, Inc.
+ */
+
+/*
+ *      
+ * Copyright (c) 2001-2006, Cisco Systems, Inc.
+ * All rights reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 
+ *   Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ * 
+ *   Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ * 
+ *   Neither the name of the Cisco Systems, Inc. nor the names of its
+ *   contributors may be used to endorse or promote products derived
+ *   from this software without specific prior written permission.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+
+#include "datatypes.h"
+#include "gf2_8.h"
+
+/* gf2_8_shift() moved to gf2_8.h as an inline function */
+
+inline gf2_8
+gf2_8_multiply(gf2_8 x, gf2_8 y) {
+  gf2_8 z = 0;
+
+  if (y &   1) z ^= x; x = gf2_8_shift(x);
+  if (y &   2) z ^= x; x = gf2_8_shift(x);
+  if (y &   4) z ^= x; x = gf2_8_shift(x);
+  if (y &   8) z ^= x; x = gf2_8_shift(x);
+  if (y &  16) z ^= x; x = gf2_8_shift(x);
+  if (y &  32) z ^= x; x = gf2_8_shift(x);
+  if (y &  64) z ^= x; x = gf2_8_shift(x);
+  if (y & 128) z ^= x; 
+  
+  return z;
+}
+
+
+/* this should use the euclidean algorithm */
+
+gf2_8
+gf2_8_compute_inverse(gf2_8 x) {
+  unsigned int i;
+
+  if (x == 0) return 0;    /* zero is a special case */
+  for (i=0; i < 256; i++)
+    if (gf2_8_multiply((gf2_8) i, x) == 1)
+      return (gf2_8) i;
+
+    return 0;
+}
+