Rename add and dup functions for Edwards curves.

1 files changed, 116 insertions, 0 deletions

diff --git a/ecc-add-thh.c b/ecc-add-thh.c
new file mode 100644
index 00000000..03bb761f
--- /dev/null
+++ b/ecc-add-thh.c
@@ -0,0 +1,116 @@
+/* ecc-add-thh.c
+
+   Copyright (C) 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/.
+*/
+
+#if HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+#include "ecc.h"
+#include "ecc-internal.h"
+
+/* Add two points on an Edwards curve, in homogeneous coordinates */
+void
+ecc_add_thh (const struct ecc_curve *ecc,
+	     mp_limb_t *r, const mp_limb_t *p, const mp_limb_t *q,
+	     mp_limb_t *scratch)
+{
+#define x1 p
+#define y1 (p + ecc->p.size)
+#define z1 (p + 2*ecc->p.size)
+
+#define x2 q
+#define y2 (q + ecc->p.size)
+#define z2 (q + 2*ecc->p.size)
+
+#define x3 r
+#define y3 (r + ecc->p.size)
+#define z3 (r + 2*ecc->p.size)
+
+  /* Formulas (from djb,
+     http://www.hyperelliptic.org/EFD/g1p/auto-twisted-projective.html#addition-add-2008-bbjlp):
+
+     Computation	Operation	Live variables
+
+     C = x1*x2		mul		C
+     D = y1*y2		mul		C, D
+     T = (x1+y1)(x2+y2) - C - D, mul	C, D, T
+     E = b*C*D		2 mul		C, E, T (Replace C <-- D - C)
+     A = z1*z2		mul		A, C, E, T
+     B = A^2		sqr		A, B, C, E, T
+     F = B - E				A, B, C, E, F, T
+     G = B + E     			A, C, F, G, T
+     x3 = A*F*T		2 mul		A, C, G
+     y3 = A*G*(D+C)	2 mul		F, G
+     z3 = F*G		mul
+
+     11M + S
+
+     We have different sign for E, hence swapping F and G, because our
+     ecc->b corresponds to -b above.
+  */
+#define C scratch
+#define D (scratch + ecc->p.size)
+#define T (scratch + 2*ecc->p.size)
+#define E (scratch + 3*ecc->p.size)
+#define A (scratch + 4*ecc->p.size)
+#define B (scratch + 5*ecc->p.size)
+#define F D
+#define G E
+
+  ecc_modp_mul (ecc, C, x1, x2);
+  ecc_modp_mul (ecc, D, y1, y2);
+  ecc_modp_add (ecc, A, x1, y1);
+  ecc_modp_add (ecc, B, x2, y2);
+  ecc_modp_mul (ecc, T, A, B);
+  ecc_modp_sub (ecc, T, T, C);
+  ecc_modp_sub (ecc, T, T, D);
+  ecc_modp_mul (ecc, x3, C, D);
+  ecc_modp_mul (ecc, E, x3, ecc->b);
+  ecc_modp_add (ecc, C, D, C);
+
+  ecc_modp_mul (ecc, A, z1, z2);
+  ecc_modp_sqr (ecc, B, A);
+
+  ecc_modp_sub (ecc, F, B, E);
+  ecc_modp_add (ecc, G, B, E);
+
+  /* x3 */
+  ecc_modp_mul (ecc, B, G, T);
+  ecc_modp_mul (ecc, x3, B, A);
+
+  /* y3 */
+  ecc_modp_mul (ecc, B, F, C);
+  ecc_modp_mul (ecc, y3, B, A);
+
+  /* z3 */
+  ecc_modp_mul (ecc, B, F, G);
+  mpn_copyi (z3, B, ecc->p.size);
+}