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);
+        }
+    }
+}