1 files changed, 112 insertions, 0 deletions
diff --git a/lib/nettle/gost/gost-point.c b/lib/nettle/gost/gost-point.c
new file mode 100644
index 0000000000..0e9938108c
--- /dev/null
+++ b/lib/nettle/gost/gost-point.c
@@ -0,0 +1,112 @@
+/* ecc-point.c
+
+   Copyright (C) 2013, 2014 Niels Möller
+
+   This file is part of GNU Nettle.
+
+   GNU Nettle is free software: you can redistribute it and/or
+   modify it under the terms of either:
+
+     * the GNU Lesser General Public License as published by the Free
+       Software Foundation; either version 3 of the License, or (at your
+       option) any later version.
+
+   or
+
+     * the GNU General Public License as published by the Free
+       Software Foundation; either version 2 of the License, or (at your
+       option) any later version.
+
+   or both in parallel, as here.
+
+   GNU Nettle 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
+   General Public License for more details.
+
+   You should have received copies of the GNU General Public License and
+   the GNU Lesser General Public License along with this program.  If
+   not, see http://www.gnu.org/licenses/.
+*/
+
+/* Development of Nettle's ECC support was funded by the .SE Internet Fund. */
+
+#if HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+#include <nettle/ecc.h>
+#include "ecc/ecc-internal.h"
+#include "ecc-gost-curve.h"
+
+int
+gost_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->p.size;
+
+  if (mpz_sgn (x) < 0 || mpz_limbs_cmp (x, p->ecc->p.m, size) >= 0
+      || mpz_sgn (y) < 0 || mpz_limbs_cmp (y, p->ecc->p.m, size) >= 0)
+    return 0;
+
+  mpz_init (lhs);
+  mpz_init (rhs);
+
+  mpz_mul (lhs, y, y);
+
+  if (p->ecc->p.bit_size == 255)
+    {
+      /* ed25519 special case. FIXME: Do in some cleaner way? */
+      mpz_t x2;
+      mpz_init (x2);
+      mpz_mul (x2, x, x);
+      mpz_mul (rhs, x2, lhs);
+      /* Check that -x^2 + y^2 = 1 - (121665/121666) x^2 y^2
+	 or 121666 (1 + x^2 - y^2) = 121665 x^2 y^2 */
+      mpz_sub (lhs, x2, lhs);
+      mpz_add_ui (lhs, lhs, 1);
+      mpz_mul_ui (lhs, lhs, 121666);
+      mpz_mul_ui (rhs, rhs, 121665);
+      mpz_clear (x2);
+    }
+  else if (p->ecc->p.bit_size == 448)
+    {
+      /* curve448 special case. FIXME: Do in some cleaner way? */
+      mpz_t x2, d;
+      mpz_init (x2);
+      mpz_init_set_ui (d, 39081);
+      mpz_mul (x2, x, x); /* x^2 */
+      mpz_mul (d, d, x2); /* 39081 x^2 */
+      mpz_set_ui (rhs, 1);
+      mpz_submul (rhs, d, lhs); /* 1 - 39081 x^2 y^2 */
+      /* Check that x^2 + y^2 = 1 - 39081 x^2 y^2 */
+      mpz_add (lhs, x2, lhs);	/* x^2 + y^2 */
+      mpz_clear (d);
+      mpz_clear (x2);
+    }
+  else
+    {
+      /* Check that y^2 = x^3 - 3*x + b (mod p) */
+      mpz_mul (rhs, x, x);
+      mpz_sub_ui (rhs, rhs, 3);
+      mpz_mul (rhs, rhs, x);
+      mpz_add (rhs, rhs, mpz_roinit_n (t, p->ecc->b, size));
+    }
+
+  res = mpz_congruent_p (lhs, rhs, mpz_roinit_n (t, p->ecc->p.m, size));
+
+  mpz_clear (lhs);
+  mpz_clear (rhs);
+
+  if (!res)
+    return 0;
+
+  mpz_limbs_copy (p->p, x, size);
+  mpz_limbs_copy (p->p + size, y, size);
+
+  return 1;
+}