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