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fix ECC

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This commit is contained in:
NIIBE Yutaka
2013-09-20 17:17:59 +09:00
parent b2fb734d57
commit ee1e1ac851
10 changed files with 131 additions and 27 deletions
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31
src/jpc.c
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@@ -1,7 +1,7 @@
/*
* jpc.c -- arithmetic on Jacobian projective coordinates and Affin coordinates
*
* Copyright (C) 2011 Free Software Initiative of Japan
* Copyright (C) 2011, 2013 Free Software Initiative of Japan
* Author: NIIBE Yutaka <gniibe@fsij.org>
*
* This file is a part of Gnuk, a GnuPG USB Token implementation.
@@ -88,6 +88,18 @@ jpc_add_ac_signed (jpc *X, const jpc *A, const ac *B, int minus)
#define y3_tmp c
#define y1_c_cube a
if (A->z == 0) /* A is infinite */
{
memcpy (X->x, B->x, sizeof (bn256));
if (minus)
bn256_sub (X->y, P256, B->y);
else
memcpy (X->y, B->y, sizeof (bn256));
memset (X->z, 0, sizeof (bn256));
X->z->words[0] = 1;
return;
}
modp256_sqr (a, A->z);
memcpy (b, a, sizeof (bn256));
modp256_mul (a, a, B->x);
@@ -101,6 +113,13 @@ jpc_add_ac_signed (jpc *X, const jpc *A, const ac *B, int minus)
else
modp256_mul (b, b, B->y);
if (bn256_cmp (A->x, a) == 0)
if (bn256_cmp (A->y, b) == 0)
{
jpc_double (X, A);
return;
}
modp256_sub (c, a, A->x);
modp256_sub (d, b, A->y);
@@ -141,16 +160,22 @@ jpc_add_ac (jpc *X, const jpc *A, const ac *B)
*
* @param X Destination AC
* @param A JPC
*
* Return -1 on error (infinite).
* Return 0 on success.
*/
void
int
jpc_to_ac (ac *X, const jpc *A)
{
bn256 z_inv[1], z_inv_sqr[1];
modp256_inv (z_inv, A->z);
if (modp256_inv (z_inv, A->z) < 0)
return -1;
modp256_sqr (z_inv_sqr, z_inv);
modp256_mul (z_inv, z_inv, z_inv_sqr);
modp256_mul (X->x, A->x, z_inv_sqr);
modp256_mul (X->y, A->y, z_inv);
return 0;
}