@Test
public void toByteArrayReturnsExpectedResult() {
for (int i = 0; i < 100; i++) {
// Arrange:
final GroupElement g = MathUtils.getRandomGroupElement();
// Act:
final byte[] gBytes = g.toByteArray();
final byte[] bytes = MathUtils.toByteArray(MathUtils.toBigInteger(g.getY()));
if (MathUtils.toBigInteger(g.getX()).mod(new BigInteger("2")).equals(BigInteger.ONE)) {
bytes[31] |= 0x80;
}
// Assert:
Assert.assertThat(Arrays.equals(gBytes, bytes), IsEqual.equalTo(true));
}
}
@Test
public void dTimesTwoIsAsExpected() {
// Arrange:
final BigInteger DTimesTwo =
new BigInteger(
"16295367250680780974490674513165176452449235426866156013048779062215315747161");
// Assert:
Assert.assertThat(DTimesTwo, IsEqual.equalTo(MathUtils.toBigInteger(Ed25519Field.D_Times_TWO)));
}
@Test
public void dIsAsExpected() {
// Arrange:
final BigInteger D =
new BigInteger(
"37095705934669439343138083508754565189542113879843219016388785533085940283555");
// Assert:
Assert.assertThat(D, IsEqual.equalTo(MathUtils.toBigInteger(Ed25519Field.D)));
}
@Test
public void iIsAsExpected() {
// Arrange:
final BigInteger I =
new BigInteger(
"19681161376707505956807079304988542015446066515923890162744021073123829784752");
// Assert (i^2 == -1):
Assert.assertThat(I, IsEqual.equalTo(MathUtils.toBigInteger(Ed25519Field.I)));
Assert.assertThat(
I.multiply(I).mod(Ed25519Field.P),
IsEqual.equalTo(BigInteger.ONE.shiftLeft(255).subtract(new BigInteger("20"))));
}
@Test
public void twoIsAsExpected() {
// Assert:
Assert.assertThat(
new BigInteger("2"), IsEqual.equalTo(MathUtils.toBigInteger(Ed25519Field.TWO)));
}
@Test
public void oneIsAsExpected() {
// Assert:
Assert.assertThat(BigInteger.ONE, IsEqual.equalTo(MathUtils.toBigInteger(Ed25519Field.ONE)));
}
@Test
public void zeroIsAsExpected() {
// Assert:
Assert.assertThat(BigInteger.ZERO, IsEqual.equalTo(MathUtils.toBigInteger(Ed25519Field.ZERO)));
}