From b5b6bd9b90eb056fdb4665ad9414d4fc627fd042 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Niels=20M=C3=B6ller?= <nisse@lysator.liu.se>
Date: Fri, 11 Jul 2014 21:57:50 +0200
Subject: [PATCH] eccdata: Corrected curve25519-related constant. And output
the constant.
---
ChangeLog | 6 ++++++
eccdata.c | 14 ++++++++------
2 files changed, 14 insertions(+), 6 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 709eded9..dd3c045c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2014-07-11 Niels Möller <nisse@lysator.liu.se>
+
+ * eccdata.c (ecc_curve_init): For curve 25519, use correct
+ constant for edwards coordinate transform, and output the constant
+ as ecc_edwards.
+
2014-07-06 Niels Möller <nisse@lysator.liu.se>
* eccdata.c: Use separate is_zero flag to represent the neutral
diff --git a/eccdata.c b/eccdata.c
index 4df2d255..ac7386de 100644
--- a/eccdata.c
+++ b/eccdata.c
@@ -565,11 +565,10 @@ ecc_curve_init (struct ecc_curve *ecc, unsigned bit_size)
*/
"20ae19a1b8a086b4e01edd2c7748d14c"
"923d4d7e6d7c61b229e9c5a27eced3d9",
- /* (121665/121666) mod p, from PARI/GP
- c = Mod(121665, p); c / (c+1)
- */
- "2dfc9311d490018c7338bf8688861767"
- "ff8ff5b2bebe27548a14b235eca6874a");
+ /* sqrt(486664) mod p, from PARI/GP
+ sqrt(Mod(486664, p)) */
+ "141b0b6806563d503de05885280b5910"
+ "9ca5ee38d7b56c9c165db7106377bbd8");
ecc->ref = ecc_alloc (3);
ecc_set_str (&ecc->ref[0], /* 2 g */
"20d342d51873f1b7d9750c687d157114"
@@ -995,7 +994,10 @@ output_curve (const struct ecc_curve *ecc, unsigned bits_per_limb)
mpz_add_ui (t, ecc->q, 1);
mpz_fdiv_q_2exp (t, t, 1);
output_bignum ("ecc_qp1h", t, limb_size, bits_per_limb);
-
+
+ if (ecc->use_edwards)
+ output_bignum ("ecc_edwards", ecc->t, limb_size, bits_per_limb);
+
/* Trailing zeros in p+1 correspond to trailing ones in p. */
redc_limbs = mpz_scan0 (ecc->p, 0) / bits_per_limb;
if (redc_limbs > 0)
--
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