Add new classes in Math.Field and some other EC-related stuff from Java

8 files changed, 255 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);
+        }
+    }
+}
diff --git a/crypto/src/math/field/GF2Polynomial.cs b/crypto/src/math/field/GF2Polynomial.cs
new file mode 100644
index 000000000..c062d508a
--- /dev/null
+++ b/crypto/src/math/field/GF2Polynomial.cs
@@ -0,0 +1,46 @@
+using System;
+
+using Org.BouncyCastle.Utilities;
+
+namespace Org.BouncyCastle.Math.Field
+{
+    internal class GF2Polynomial
+        : IPolynomial
+    {
+        protected readonly int[] exponents;
+
+        internal GF2Polynomial(int[] exponents)
+        {
+            this.exponents = Arrays.Clone(exponents);
+        }
+
+        public virtual int Degree
+        {
+            get { return exponents[exponents.Length - 1]; }
+        }
+
+        public virtual int[] GetExponentsPresent()
+        {
+            return Arrays.Clone(exponents);
+        }
+
+        public override bool Equals(object obj)
+        {
+            if (this == obj)
+            {
+                return true;
+            }
+            GF2Polynomial other = obj as GF2Polynomial;
+            if (null == other)
+            {
+                return false;
+            }
+            return Arrays.AreEqual(exponents, other.exponents);
+        }
+
+        public override int GetHashCode()
+        {
+            return Arrays.GetHashCode(exponents);
+        }
+    }
+}
diff --git a/crypto/src/math/field/GenericPolynomialExtensionField.cs b/crypto/src/math/field/GenericPolynomialExtensionField.cs
new file mode 100644
index 000000000..13ef57165
--- /dev/null
+++ b/crypto/src/math/field/GenericPolynomialExtensionField.cs
@@ -0,0 +1,63 @@
+using System;
+
+using Org.BouncyCastle.Utilities;
+
+namespace Org.BouncyCastle.Math.Field
+{
+    internal class GenericPolynomialExtensionField
+        : IPolynomialExtensionField
+    {
+        protected readonly IFiniteField subfield;
+        protected readonly IPolynomial minimalPolynomial;
+
+        internal GenericPolynomialExtensionField(IFiniteField subfield, IPolynomial polynomial)
+        {
+            this.subfield = subfield;
+            this.minimalPolynomial = polynomial;
+        }
+
+        public virtual BigInteger Characteristic
+        {
+            get { return subfield.Characteristic; }
+        }
+
+        public virtual int Dimension
+        {
+            get { return subfield.Dimension * minimalPolynomial.Degree; }
+        }
+
+        public virtual IFiniteField Subfield
+        {
+            get { return subfield; }
+        }
+
+        public virtual int Degree
+        {
+            get { return minimalPolynomial.Degree; }
+        }
+
+        public virtual IPolynomial MinimalPolynomial
+        {
+            get { return minimalPolynomial; }
+        }
+
+        public override bool Equals(object obj)
+        {
+            if (this == obj)
+            {
+                return true;
+            }
+            GenericPolynomialExtensionField other = obj as GenericPolynomialExtensionField;
+            if (null == other)
+            {
+                return false;
+            }
+            return subfield.Equals(other.subfield) && minimalPolynomial.Equals(other.minimalPolynomial);
+        }
+
+        public override int GetHashCode()
+        {
+            return subfield.GetHashCode() ^ Integers.RotateLeft(minimalPolynomial.GetHashCode(), 16);
+        }
+    }
+}
diff --git a/crypto/src/math/field/IExtensionField.cs b/crypto/src/math/field/IExtensionField.cs
new file mode 100644
index 000000000..17f45c153
--- /dev/null
+++ b/crypto/src/math/field/IExtensionField.cs
@@ -0,0 +1,12 @@
+using System;
+
+namespace Org.BouncyCastle.Math.Field
+{
+    public interface IExtensionField
+        : IFiniteField
+    {
+        IFiniteField Subfield { get; }
+
+        int Degree { get; }
+    }
+}
diff --git a/crypto/src/math/field/IFiniteField.cs b/crypto/src/math/field/IFiniteField.cs
new file mode 100644
index 000000000..b618be74b
--- /dev/null
+++ b/crypto/src/math/field/IFiniteField.cs
@@ -0,0 +1,11 @@
+using System;
+
+namespace Org.BouncyCastle.Math.Field
+{
+    public interface IFiniteField
+    {
+        BigInteger Characteristic { get; }
+
+        int Dimension { get; }
+    }
+}
diff --git a/crypto/src/math/field/IPolynomial.cs b/crypto/src/math/field/IPolynomial.cs
new file mode 100644
index 000000000..ad6dfb662
--- /dev/null
+++ b/crypto/src/math/field/IPolynomial.cs
@@ -0,0 +1,15 @@
+using System;
+
+namespace Org.BouncyCastle.Math.Field
+{
+    public interface IPolynomial
+    {
+        int Degree { get; }
+
+        //BigInteger[] GetCoefficients();
+
+        int[] GetExponentsPresent();
+
+        //Term[] GetNonZeroTerms();
+    }
+}
diff --git a/crypto/src/math/field/IPolynomialExtensionField.cs b/crypto/src/math/field/IPolynomialExtensionField.cs
new file mode 100644
index 000000000..3818c1855
--- /dev/null
+++ b/crypto/src/math/field/IPolynomialExtensionField.cs
@@ -0,0 +1,10 @@
+using System;
+
+namespace Org.BouncyCastle.Math.Field
+{
+    public interface IPolynomialExtensionField
+        : IExtensionField
+    {
+        IPolynomial MinimalPolynomial { get; }
+    }
+}
diff --git a/crypto/src/math/field/PrimeField.cs b/crypto/src/math/field/PrimeField.cs
new file mode 100644
index 000000000..f6ba629d5
--- /dev/null
+++ b/crypto/src/math/field/PrimeField.cs
@@ -0,0 +1,44 @@
+using System;
+
+namespace Org.BouncyCastle.Math.Field
+{
+    internal class PrimeField
+        : IFiniteField
+    {
+        protected readonly BigInteger characteristic;
+
+        internal PrimeField(BigInteger characteristic)
+        {
+            this.characteristic = characteristic;
+        }
+
+        public virtual BigInteger Characteristic
+        {
+            get { return characteristic; }
+        }
+
+        public virtual int Dimension
+        {
+            get { return 1; }
+        }
+
+        public override bool Equals(object obj)
+        {
+            if (this == obj)
+            {
+                return true;
+            }
+            PrimeField other = obj as PrimeField;
+            if (null == other)
+            {
+                return false;
+            }
+            return characteristic.Equals(other.characteristic);
+        }
+
+        public override int GetHashCode()
+        {
+            return characteristic.GetHashCode();
+        }
+    }
+}