using System; namespace Org.BouncyCastle.Math.Field { public abstract class FiniteFields { internal static readonly IFiniteField GF_2 = new PrimeField(BigInteger.Two); internal static readonly IFiniteField GF_3 = new PrimeField(BigInteger.Three); 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 monotonically increasing", "exponents"); } return new GenericPolynomialExtensionField(GF_2, new GF2Polynomial(exponents)); } 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); } } }