1 files changed, 61 insertions, 0 deletions
diff --git a/rsa-verify.c b/rsa-verify.c
new file mode 100644
index 00000000..7a6d381f
--- /dev/null
+++ b/rsa-verify.c
@@ -0,0 +1,61 @@
+/* rsa-verify.c
+ *
+ * Verifying RSA signatures.
+ */
+
+/* nettle, low-level cryptographics library
+ *
+ * Copyright (C) 2001, 2003 Niels Möller
+ *  
+ * The nettle library is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2.1 of the License, or (at your
+ * option) any later version.
+ * 
+ * The nettle library is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
+ * License for more details.
+ * 
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with the nettle library; see the file COPYING.LIB.  If not, write to
+ * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+
+#if HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#if WITH_PUBLIC_KEY
+
+#include "rsa.h"
+
+#include "bignum.h"
+
+int
+_rsa_verify(const struct rsa_public_key *key,
+	    const mpz_t m,
+	    const mpz_t s)
+{
+  int res;
+  
+  mpz_t m1;
+  
+  if ( (mpz_sgn(s) <= 0)
+       || (mpz_cmp(s, key->n) >= 0) )
+    return 0;
+       
+  mpz_init(m1);
+  
+  mpz_powm(m1, s, key->e, key->n);
+
+  /* FIXME: Is it cheaper to convert m1 to a string and check that? */
+  res = !mpz_cmp(m, m1);
+
+  mpz_clear(m1);
+
+  return res;
+}
+
+#endif /* WITH_PUBLIC_KEY */