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Fix for constant time (step 9)

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NIIBE Yutaka
2014-01-23 15:34:18 +09:00
parent 36541838f9
commit 78ffb4179e
2 changed files with 15 additions and 4 deletions
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2
ChangeLog
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@@ -1,5 +1,7 @@
2014-01-23 Niibe Yutaka <gniibe@fsij.org> 2014-01-23 Niibe Yutaka <gniibe@fsij.org>
* src/jpc.c (jpc_add_ac_signed): Fix for constant time.
* src/ec_p256.c (ecdsa): Bug fix for k selection. * src/ec_p256.c (ecdsa): Bug fix for k selection.
2014-01-22 Niibe Yutaka <gniibe@fsij.org> 2014-01-22 Niibe Yutaka <gniibe@fsij.org>

17
src/jpc.c
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@@ -81,7 +81,7 @@ jpc_double (jpc *X, const jpc *A)
void void
jpc_add_ac_signed (jpc *X, const jpc *A, const ac *B, int minus) jpc_add_ac_signed (jpc *X, const jpc *A, const ac *B, int minus)
{ {
bn256 a[1], b[1], c[1], d[1]; bn256 a[1], b[1], c[1], d[1], tmp[1];
#define minus_B_y c #define minus_B_y c
#define c_sqr a #define c_sqr a
#define c_cube b #define c_cube b
@@ -96,9 +96,15 @@ jpc_add_ac_signed (jpc *X, const jpc *A, const ac *B, int minus)
{ {
memcpy (X->x, B->x, sizeof (bn256)); memcpy (X->x, B->x, sizeof (bn256));
if (minus) if (minus)
bn256_sub (X->y, P256, B->y); {
memcpy (tmp, B->y, sizeof (bn256));
bn256_sub (X->y, P256, B->y);
}
else else
memcpy (X->y, B->y, sizeof (bn256)); {
memcpy (X->y, B->y, sizeof (bn256));
bn256_sub (tmp, P256, B->y);
}
memset (X->z, 0, sizeof (bn256)); memset (X->z, 0, sizeof (bn256));
X->z->word[0] = 1; X->z->word[0] = 1;
return; return;
@@ -115,7 +121,10 @@ jpc_add_ac_signed (jpc *X, const jpc *A, const ac *B, int minus)
modp256_mul (b, b, minus_B_y); modp256_mul (b, b, minus_B_y);
} }
else else
modp256_mul (b, b, B->y); {
bn256_sub (tmp, P256, B->y);
modp256_mul (b, b, B->y);
}
if (bn256_cmp (A->x, a) == 0 && bn256_cmp (A->y, b) == 0) if (bn256_cmp (A->x, a) == 0 && bn256_cmp (A->y, b) == 0)
{ {