1 files changed, 54 insertions, 0 deletions
diff --git a/crypto/src/math/field/FiniteFields.cs b/crypto/src/math/field/FiniteFields.cs
new file mode 100644
index 000000000..7b84569fe
--- /dev/null
+++ b/crypto/src/math/field/FiniteFields.cs
@@ -0,0 +1,54 @@
+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);
+ }
+ }
+}
|
