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handle negative scalars correctly when doing point multiplication

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This commit is contained in:
Bodo Möller 2001-03-11 08:44:50 +00:00
parent 616df35633
commit 86a921af06
2 changed files with 25 additions and 2 deletions
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8
crypto/ec/ec_mult.c
View File

@ -187,10 +187,18 @@ int EC_POINTs_mul(const EC_GROUP *group, EC_POINT *r, BIGNUM *scalar,
if (i < num) if (i < num)
{ {
if (!EC_POINT_copy(val_sub[i][0], points[i])) goto err; if (!EC_POINT_copy(val_sub[i][0], points[i])) goto err;
if (scalars[i]->neg)
{
if (!EC_POINT_invert(group, val_sub[i][0], ctx)) goto err;
}
} }
else else
{ {
if (!EC_POINT_copy(val_sub[i][0], generator)) goto err; if (!EC_POINT_copy(val_sub[i][0], generator)) goto err;
if (scalar->neg)
{
if (!EC_POINT_invert(group, val_sub[i][0], ctx)) goto err;
}
} }
if (wsize[i] > 1) if (wsize[i] > 1)

19
crypto/ec/ectest.c
View File

@ -519,7 +519,7 @@ int main(int argc, char *argv[])
scalars[0] = y; /* (group order + 1)/2, so y*Q + y*Q = Q */ scalars[0] = y; /* (group order + 1)/2, so y*Q + y*Q = Q */
scalars[1] = y; scalars[1] = y;
fprintf(stdout, "simultaneous multiplication ... "); fprintf(stdout, "simultaneous multiplication ...");
fflush(stdout); fflush(stdout);
/* z is still the group order */ /* z is still the group order */
@ -528,7 +528,22 @@ int main(int argc, char *argv[])
if (0 != EC_POINT_cmp(group, P, R, ctx)) ABORT; if (0 != EC_POINT_cmp(group, P, R, ctx)) ABORT;
if (0 != EC_POINT_cmp(group, R, Q, ctx)) ABORT; if (0 != EC_POINT_cmp(group, R, Q, ctx)) ABORT;
fprintf(stdout, "ok\n\n"); fprintf(stdout, ".");
fflush(stdout);
if (!BN_pseudo_rand(y, BN_num_bits(y), 0, 0)) ABORT;
if (!BN_copy(z, y)) ABORT;
z->neg = 1;
points[0] = Q;
points[1] = Q;
scalars[0] = y;
scalars[1] = z;
if (!EC_POINTs_mul(group, P, NULL, 2, points, scalars, ctx)) ABORT;
if (!EC_POINT_is_at_infinity(group, P)) ABORT;
fprintf(stdout, " ok\n\n");
} }