New files.

Rev: src/nettle/dsa-sign.c:1.1
Rev: src/nettle/dsa-verify.c:1.1
Rev: src/nettle/dsa.c:1.1
Rev: src/nettle/dsa.h:1.1

1 files changed, 100 insertions, 0 deletions

diff --git a/dsa-verify.c b/dsa-verify.c
new file mode 100644
index 00000000..ba73d344
--- /dev/null
+++ b/dsa-verify.c
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+/* dsa-verify.c
+ *
+ * The DSA publickey algorithm.
+ */
+
+/* nettle, low-level cryptographics library
+ *
+ * Copyright (C) 2002 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 "dsa.h"
+
+#include <stdlib.h>
+
+int
+dsa_verify(struct dsa_public_key *key,
+	   struct sha1_ctx *hash,
+	   const struct dsa_signature *signature)
+{
+  mpz_t w;
+  mpz_t tmp;
+  mpz_t v;
+
+  int res;
+  
+  /* Check that r and s are in the proper range */
+  if (mpz_sgn(signature->r) <= 0 || mpz_cmp(signature->r, key->q) >= 0)
+    return 0;
+
+  if (mpz_sgn(signature->s) <= 0 || mpz_cmp(signature->s, key->q) >= 0)
+    return 0;
+
+  mpz_init(w);
+
+  /* Compute w = s^-1 (mod q) */
+
+  /* NOTE: In gmp-2, mpz_invert sometimes generates negative inverses,
+   * so we need gmp-3 or better. */
+  if (!mpz_invert(w, signature->s, key->q))
+    {
+      mpz_clear(w);
+      return 0;
+    }
+
+  mpz_init(tmp);
+  mpz_init(v);
+  
+  /* Compute hash */
+  _dsa_hash(tmp, hash);
+  
+  /* v = g^{w * h (mod q)} (mod p)  */
+
+  mpz_mul(tmp, tmp, w);
+  mpz_fdiv_r(tmp, tmp, key->q);
+
+  mpz_powm(v, key->g, tmp, key->p);
+
+  /* y^{w * r (mod q) } (mod p) */
+  mpz_mul(tmp, signature->r, w);
+  mpz_fdiv_r(tmp, tmp, key->q);
+
+  mpz_powm(tmp, key->y, tmp, key->p);
+
+  /* v = (g^{w * h} * y^{w * r} (mod p) ) (mod q) */
+  mpz_mul(v, v, tmp);
+  mpz_fdiv_r(v, v, key->p);
+
+  mpz_fdiv_r(v, v, key->q);
+
+  res = !mpz_cmp(v, signature->r);
+
+  mpz_clear(w);
+  mpz_clear(tmp);
+  mpz_clear(v);
+
+  return res;
+}
+
+#endif /* WITH_PUBLIC_KEY */