Integrated ECDSA sign and verify functions.

1 files changed, 90 insertions, 0 deletions

diff --git a/ecc-point.c b/ecc-point.c
new file mode 100644
index 00000000..b26c192e
--- /dev/null
+++ b/ecc-point.c
@@ -0,0 +1,90 @@
+/* ecc-point.c */
+
+/* nettle, low-level cryptographics library
+ *
+ * Copyright (C) 2013 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., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02111-1301, USA.
+ */
+
+/* Development of Nettle's ECC support was funded by Internetfonden. */
+
+#if HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+#include "ecc.h"
+#include "ecc-internal.h"
+#include "gmp-glue.h"
+
+void
+ecc_point_init (struct ecc_point *p, const struct ecc_curve *ecc)
+{
+  p->ecc = ecc;
+  p->p = _gmp_alloc_limbs (2*ecc->size);
+}
+
+void
+ecc_point_clear (struct ecc_point *p)
+{
+  _gmp_free_limbs (p->p, 2*p->ecc->size);
+}
+
+int
+ecc_point_set (struct ecc_point *p, const mpz_t x, const mpz_t y)
+{
+  mp_size_t size;  
+  mpz_t lhs, rhs;
+  mpz_t t;
+  int res;
+
+  size = p->ecc->size;
+  
+  if (mpz_sgn (x) < 0 || _mpz_cmp_limbs (x, p->ecc->p, size) >= 0
+      || mpz_sgn (y) < 0 || _mpz_cmp_limbs (y, p->ecc->p, size) >= 0)
+    return 0;
+
+  mpz_init (lhs);
+  mpz_init (rhs);
+
+  /* Check that y^2 = x^3 - 3*x + b (mod p) */
+  mpz_mul (lhs, y, y);
+  mpz_mul (rhs, x, x);
+  mpz_sub_ui (rhs, rhs, 3);
+  mpz_mul (rhs, rhs, x);
+  mpz_add (rhs, rhs, _mpz_init_mpn (t, p->ecc->b, size));
+
+  res = mpz_congruent_p (lhs, rhs, _mpz_init_mpn (t, p->ecc->p, size));
+
+  mpz_clear (lhs);
+  mpz_clear (rhs);
+
+  if (!res)
+    return 0;
+
+  _mpz_copy_limbs (p->p, x, size);
+  _mpz_copy_limbs (p->p + size, y, size);
+
+  return 1;
+}
+
+void
+ecc_point_get (const struct ecc_point *p, mpz_t x, mpz_t y)
+{
+  mp_size_t size = p->ecc->size;
+  _mpz_set_mpn (x, p->p, size);
+  _mpz_set_mpn (y, p->p + size, size);
+}