FiniteFields.cs
1.76 KB
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using System;
namespace Org.BouncyCastle.Math.Field
{
public abstract class FiniteFields
{
internal static readonly IFiniteField GF_2 = new PrimeField(BigInteger.ValueOf(2));
internal static readonly IFiniteField GF_3 = new PrimeField(BigInteger.ValueOf(3));
public static IPolynomialExtensionField GetBinaryExtensionField(int[] exponents)
{
if (exponents[0] != 0)
{
throw new ArgumentException("Irreducible polynomials in GF(2) must have constant term", "exponents");
}
for (int i = 1; i < exponents.Length; ++i)
{
if (exponents[i] <= exponents[i - 1])
{
throw new ArgumentException("Polynomial exponents must be montonically increasing", "exponents");
}
}
return new GenericPolynomialExtensionField(GF_2, new GF2Polynomial(exponents));
}
// public static IPolynomialExtensionField GetTernaryExtensionField(Term[] terms)
// {
// return new GenericPolynomialExtensionField(GF_3, new GF3Polynomial(terms));
// }
public static IFiniteField GetPrimeField(BigInteger characteristic)
{
int bitLength = characteristic.BitLength;
if (characteristic.SignValue <= 0 || bitLength < 2)
{
throw new ArgumentException("Must be >= 2", "characteristic");
}
if (bitLength < 3)
{
switch (characteristic.IntValue)
{
case 2:
return GF_2;
case 3:
return GF_3;
}
}
return new PrimeField(characteristic);
}
}
}