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Merge pull request #42 from romanz/master

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bignum: use constant time comparisons
This commit is contained in:
Pavol Rusnak 2015-08-03 21:46:53 +02:00
commit 9255595c97
2 changed files with 53 additions and 7 deletions
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18
bignum.c
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@ -88,28 +88,32 @@ void bn_zero(bignum256 *a)
int bn_is_zero(const bignum256 *a)
{
int i;
uint32_t result = 0;
for (i = 0; i < 9; i++) {
if (a->val[i] != 0) return 0;
result |= a->val[i];
}
return 1;
return !result;
}
int bn_is_less(const bignum256 *a, const bignum256 *b)
{
int i;
uint32_t res1 = 0;
uint32_t res2 = 0;
for (i = 8; i >= 0; i--) {
if (a->val[i] < b->val[i]) return 1;
if (a->val[i] > b->val[i]) return 0;
res1 = (res1 << 1) | (a->val[i] < b->val[i]);
res2 = (res2 << 1) | (a->val[i] > b->val[i]);
}
return 0;
return res1 > res2;
}
int bn_is_equal(const bignum256 *a, const bignum256 *b) {
int i;
uint32_t result = 0;
for (i = 0; i < 9; i++) {
if (a->val[i] != b->val[i]) return 0;
result |= (a->val[i] ^ b->val[i]);
}
return 1;
return !result;
}
int bn_bitlen(const bignum256 *a) {

42
test_curves.py
View File

@ -97,6 +97,48 @@ def test_inverse(curve, r):
assert y == y_
def test_is_less(curve, r):
x = r.randrange(0, curve.p)
y = r.randrange(0, curve.p)
x_ = int2bn(x)
y_ = int2bn(y)
res = lib.bn_is_less(x_, y_)
assert res == (x < y)
res = lib.bn_is_less(y_, x_)
assert res == (y < x)
def test_is_equal(curve, r):
x = r.randrange(0, curve.p)
y = r.randrange(0, curve.p)
x_ = int2bn(x)
y_ = int2bn(y)
assert lib.bn_is_equal(x_, y_) == (x == y)
assert lib.bn_is_equal(x_, x_) == 1
assert lib.bn_is_equal(y_, y_) == 1
def test_is_zero(curve, r):
x = r.randrange(0, curve.p);
assert lib.bn_is_zero(int2bn(x)) == (not x)
def test_simple_comparisons():
assert lib.bn_is_zero(int2bn(0)) == 1
assert lib.bn_is_zero(int2bn(1)) == 0
assert lib.bn_is_less(int2bn(0), int2bn(0)) == 0
assert lib.bn_is_less(int2bn(1), int2bn(0)) == 0
assert lib.bn_is_less(int2bn(0), int2bn(1)) == 1
assert lib.bn_is_equal(int2bn(0), int2bn(0)) == 1
assert lib.bn_is_equal(int2bn(1), int2bn(0)) == 0
assert lib.bn_is_equal(int2bn(0), int2bn(1)) == 0
def test_mult_half(curve, r):
x = r.randrange(0, 2*curve.p)
y = int2bn(x)