org.bouncycastle.math.field.FiniteFields Maven / Gradle / Ivy
package org.bouncycastle.math.field;
import java.math.BigInteger;
public abstract class FiniteFields
{
static final FiniteField GF_2 = new PrimeField(BigInteger.valueOf(2));
static final FiniteField GF_3 = new PrimeField(BigInteger.valueOf(3));
public static PolynomialExtensionField getBinaryExtensionField(int[] exponents)
{
if (exponents[0] != 0)
{
throw new IllegalArgumentException("Irreducible polynomials in GF(2) must have constant term");
}
for (int i = 1; i < exponents.length; ++i)
{
if (exponents[i] <= exponents[i - 1])
{
throw new IllegalArgumentException("Polynomial exponents must be monotonically increasing");
}
}
return new GenericPolynomialExtensionField(GF_2, new GF2Polynomial(exponents));
}
// public static PolynomialExtensionField getTernaryExtensionField(Term[] terms)
// {
// return new GenericPolynomialExtensionField(GF_3, new GF3Polynomial(terms));
// }
public static FiniteField getPrimeField(BigInteger characteristic)
{
int bitLength = characteristic.bitLength();
if (characteristic.signum() <= 0 || bitLength < 2)
{
throw new IllegalArgumentException("'characteristic' must be >= 2");
}
if (bitLength < 3)
{
switch (characteristic.intValue())
{
case 2:
return GF_2;
case 3:
return GF_3;
}
}
return new PrimeField(characteristic);
}
}