From 8405b5610adc2405c7cb1d2b25150388728adba6 Mon Sep 17 00:00:00 2001
From: Peter Dettman <peter.dettman@bouncycastle.org>
Date: Sat, 1 Feb 2014 19:10:28 +0700
Subject: Add custom curve for secp521r1 (P-521)

---
 .../math/ec/custom/sec/SecP521R1FieldElement.cs    | 166 +++++++++++++++++++++
 1 file changed, 166 insertions(+)
 create mode 100644 crypto/src/math/ec/custom/sec/SecP521R1FieldElement.cs

(limited to 'crypto/src/math/ec/custom/sec/SecP521R1FieldElement.cs')

diff --git a/crypto/src/math/ec/custom/sec/SecP521R1FieldElement.cs b/crypto/src/math/ec/custom/sec/SecP521R1FieldElement.cs
new file mode 100644
index 000000000..e47a199f3
--- /dev/null
+++ b/crypto/src/math/ec/custom/sec/SecP521R1FieldElement.cs
@@ -0,0 +1,166 @@
+using System;
+
+using Org.BouncyCastle.Utilities;
+
+namespace Org.BouncyCastle.Math.EC.Custom.Sec
+{
+    internal class SecP521R1FieldElement
+        : ECFieldElement
+    {
+        public static readonly BigInteger Q = SecP521R1Curve.q;
+
+        protected internal readonly uint[] x;
+
+        public SecP521R1FieldElement(BigInteger x)
+        {
+            if (x == null || x.SignValue < 0 || x.CompareTo(Q) >= 0)
+                throw new ArgumentException("value invalid for SecP521R1FieldElement", "x");
+
+            this.x = SecP521R1Field.FromBigInteger(x);
+        }
+
+        public SecP521R1FieldElement()
+        {
+            this.x = Nat.Create(17);
+        }
+
+        protected internal SecP521R1FieldElement(uint[] x)
+        {
+            this.x = x;
+        }
+
+        public override bool IsZero
+        {
+            get { return Nat.IsZero(17, x); }
+        }
+
+        public override bool IsOne
+        {
+            get { return Nat.IsOne(17, x); }
+        }
+
+        public override bool TestBitZero()
+        {
+            return Nat.GetBit(x, 0) == 1;
+        }
+
+        public override BigInteger ToBigInteger()
+        {
+            return Nat.ToBigInteger(17, x);
+        }
+
+        public override string FieldName
+        {
+            get { return "SecP521R1Field"; }
+        }
+
+        public override int FieldSize
+        {
+            get { return Q.BitLength; }
+        }
+
+        public override ECFieldElement Add(ECFieldElement b)
+        {
+            uint[] z = Nat.Create(17);
+            SecP521R1Field.Add(x, ((SecP521R1FieldElement)b).x, z);
+            return new SecP521R1FieldElement(z);
+        }
+
+        public override ECFieldElement AddOne()
+        {
+            uint[] z = Nat.Create(17);
+            SecP521R1Field.AddOne(x, z);
+            return new SecP521R1FieldElement(z);
+        }
+
+        public override ECFieldElement Subtract(ECFieldElement b)
+        {
+            uint[] z = Nat.Create(17);
+            SecP521R1Field.Subtract(x, ((SecP521R1FieldElement)b).x, z);
+            return new SecP521R1FieldElement(z);
+        }
+
+        public override ECFieldElement Multiply(ECFieldElement b)
+        {
+            uint[] z = Nat.Create(17);
+            SecP521R1Field.Multiply(x, ((SecP521R1FieldElement)b).x, z);
+            return new SecP521R1FieldElement(z);
+        }
+
+        public override ECFieldElement Divide(ECFieldElement b)
+        {
+            //return Multiply(b.Invert());
+            uint[] z = Nat.Create(17);
+            Mod.Invert(SecP521R1Field.P, ((SecP521R1FieldElement)b).x, z);
+            SecP521R1Field.Multiply(z, x, z);
+            return new SecP521R1FieldElement(z);
+        }
+
+        public override ECFieldElement Negate()
+        {
+            uint[] z = Nat.Create(17);
+            SecP521R1Field.Negate(x, z);
+            return new SecP521R1FieldElement(z);
+        }
+
+        public override ECFieldElement Square()
+        {
+            uint[] z = Nat.Create(17);
+            SecP521R1Field.Square(x, z);
+            return new SecP521R1FieldElement(z);
+        }
+
+        public override ECFieldElement Invert()
+        {
+            //return new SecP521R1FieldElement(ToBigInteger().ModInverse(Q));
+            uint[] z = Nat.Create(17);
+            Mod.Invert(SecP521R1Field.P, x, z);
+            return new SecP521R1FieldElement(z);
+        }
+
+        /**
+         * return a sqrt root - the routine verifies that the calculation returns the right value - if
+         * none exists it returns null.
+         */
+        public override ECFieldElement Sqrt()
+        {
+            // Raise this element to the exponent 2^519
+
+            uint[] x1 = this.x;
+            if (Nat.IsZero(17, x1) || Nat.IsOne(17, x1))
+                return this;
+
+            uint[] t1 = Nat.Create(17);
+            uint[] t2 = Nat.Create(17);
+
+            SecP521R1Field.SquareN(x1, 519, t1);
+            SecP521R1Field.Square(t1, t2);
+
+            return Arrays.AreEqual(x1, t2) ? new SecP521R1FieldElement(t1) : null;
+        }
+
+        public override bool Equals(object obj)
+        {
+            return Equals(obj as SecP521R1FieldElement);
+        }
+
+        public override bool Equals(ECFieldElement other)
+        {
+            return Equals(other as SecP521R1FieldElement);
+        }
+
+        public virtual bool Equals(SecP521R1FieldElement other)
+        {
+            if (this == other)
+                return true;
+            if (null == other)
+                return false;
+            return Arrays.AreEqual(x, other.x);
+        }
+
+        public override int GetHashCode()
+        {
+            return Q.GetHashCode() ^ Arrays.GetHashCode(x);
+        }
+    }
+}
-- 
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