From d9767a579945e47b5667e336c6dec2f40dc95f72 Mon Sep 17 00:00:00 2001
From: Gilles Peskine <Gilles.Peskine@arm.com>
Date: Fri, 14 Sep 2018 19:29:47 +0200
Subject: [PATCH] Tweak ECP self-test to work with secp192k1
The constants used in the test worked with every supported curve
except secp192k1. For secp192k1, the "N-1" exponent was too large.
Signed-off-by: Gilles Peskine <gilles.peskine@arm.com>
---
library/ecp.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/library/ecp.c b/library/ecp.c
index ab5ab9585..00917e842 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -3303,11 +3303,13 @@ int mbedtls_ecp_self_test( int verbose )
mbedtls_ecp_point R, P;
mbedtls_mpi m;
unsigned long add_c_prev, dbl_c_prev, mul_c_prev;
- /* exponents especially adapted for secp192r1 */
+ /* Exponents especially adapted for secp192k1, which has the lowest
+ * order n of all supported curves (secp192r1 is in a slightly larger
+ * field but the order of its base point is slightly smaller). */
const char *exponents[] =
{
"000000000000000000000000000000000000000000000001", /* one */
- "FFFFFFFFFFFFFFFFFFFFFFFF99DEF836146BC9B1B4D22830", /* N - 1 */
+ "FFFFFFFFFFFFFFFFFFFFFFFE26F2FC170F69466A74DEFD8C", /* n - 1 */
"5EA6F389A38B8BC81E767753B15AA5569E1782E30ABE7D25", /* random */
"400000000000000000000000000000000000000000000000", /* one and zeros */
"7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF", /* all ones */