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- #if !BESTHTTP_DISABLE_ALTERNATE_SSL && (!UNITY_WEBGL || UNITY_EDITOR)
- using System;
- using Org.BouncyCastle.Math.Raw;
- using Org.BouncyCastle.Utilities;
- namespace Org.BouncyCastle.Math.EC.Custom.Djb
- {
- internal class Curve25519FieldElement
- : ECFieldElement
- {
- public static readonly BigInteger Q = Curve25519.q;
- // Calculated as ECConstants.TWO.modPow(Q.shiftRight(2), Q)
- private static readonly uint[] PRECOMP_POW2 = new uint[]{ 0x4a0ea0b0, 0xc4ee1b27, 0xad2fe478, 0x2f431806,
- 0x3dfbd7a7, 0x2b4d0099, 0x4fc1df0b, 0x2b832480 };
- protected internal readonly uint[] x;
- public Curve25519FieldElement(BigInteger x)
- {
- if (x == null || x.SignValue < 0 || x.CompareTo(Q) >= 0)
- throw new ArgumentException("value invalid for Curve25519FieldElement", "x");
- this.x = Curve25519Field.FromBigInteger(x);
- }
- public Curve25519FieldElement()
- {
- this.x = Nat256.Create();
- }
- protected internal Curve25519FieldElement(uint[] x)
- {
- this.x = x;
- }
- public override bool IsZero
- {
- get { return Nat256.IsZero(x); }
- }
- public override bool IsOne
- {
- get { return Nat256.IsOne(x); }
- }
- public override bool TestBitZero()
- {
- return Nat256.GetBit(x, 0) == 1;
- }
- public override BigInteger ToBigInteger()
- {
- return Nat256.ToBigInteger(x);
- }
- public override string FieldName
- {
- get { return "Curve25519Field"; }
- }
- public override int FieldSize
- {
- get { return Q.BitLength; }
- }
- public override ECFieldElement Add(ECFieldElement b)
- {
- uint[] z = Nat256.Create();
- Curve25519Field.Add(x, ((Curve25519FieldElement)b).x, z);
- return new Curve25519FieldElement(z);
- }
- public override ECFieldElement AddOne()
- {
- uint[] z = Nat256.Create();
- Curve25519Field.AddOne(x, z);
- return new Curve25519FieldElement(z);
- }
- public override ECFieldElement Subtract(ECFieldElement b)
- {
- uint[] z = Nat256.Create();
- Curve25519Field.Subtract(x, ((Curve25519FieldElement)b).x, z);
- return new Curve25519FieldElement(z);
- }
- public override ECFieldElement Multiply(ECFieldElement b)
- {
- uint[] z = Nat256.Create();
- Curve25519Field.Multiply(x, ((Curve25519FieldElement)b).x, z);
- return new Curve25519FieldElement(z);
- }
- public override ECFieldElement Divide(ECFieldElement b)
- {
- //return Multiply(b.Invert());
- uint[] z = Nat256.Create();
- Mod.Invert(Curve25519Field.P, ((Curve25519FieldElement)b).x, z);
- Curve25519Field.Multiply(z, x, z);
- return new Curve25519FieldElement(z);
- }
- public override ECFieldElement Negate()
- {
- uint[] z = Nat256.Create();
- Curve25519Field.Negate(x, z);
- return new Curve25519FieldElement(z);
- }
- public override ECFieldElement Square()
- {
- uint[] z = Nat256.Create();
- Curve25519Field.Square(x, z);
- return new Curve25519FieldElement(z);
- }
- public override ECFieldElement Invert()
- {
- //return new Curve25519FieldElement(ToBigInteger().ModInverse(Q));
- uint[] z = Nat256.Create();
- Mod.Invert(Curve25519Field.P, x, z);
- return new Curve25519FieldElement(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()
- {
- /*
- * Q == 8m + 5, so we use Pocklington's method for this case.
- *
- * First, raise this element to the exponent 2^252 - 2^1 (i.e. m + 1)
- *
- * Breaking up the exponent's binary representation into "repunits", we get:
- * { 251 1s } { 1 0s }
- *
- * Therefore we need an addition chain containing 251 (the lengths of the repunits)
- * We use: 1, 2, 3, 4, 7, 11, 15, 30, 60, 120, 131, [251]
- */
- uint[] x1 = this.x;
- if (Nat256.IsZero(x1) || Nat256.IsOne(x1))
- return this;
- uint[] x2 = Nat256.Create();
- Curve25519Field.Square(x1, x2);
- Curve25519Field.Multiply(x2, x1, x2);
- uint[] x3 = x2;
- Curve25519Field.Square(x2, x3);
- Curve25519Field.Multiply(x3, x1, x3);
- uint[] x4 = Nat256.Create();
- Curve25519Field.Square(x3, x4);
- Curve25519Field.Multiply(x4, x1, x4);
- uint[] x7 = Nat256.Create();
- Curve25519Field.SquareN(x4, 3, x7);
- Curve25519Field.Multiply(x7, x3, x7);
- uint[] x11 = x3;
- Curve25519Field.SquareN(x7, 4, x11);
- Curve25519Field.Multiply(x11, x4, x11);
- uint[] x15 = x7;
- Curve25519Field.SquareN(x11, 4, x15);
- Curve25519Field.Multiply(x15, x4, x15);
- uint[] x30 = x4;
- Curve25519Field.SquareN(x15, 15, x30);
- Curve25519Field.Multiply(x30, x15, x30);
- uint[] x60 = x15;
- Curve25519Field.SquareN(x30, 30, x60);
- Curve25519Field.Multiply(x60, x30, x60);
- uint[] x120 = x30;
- Curve25519Field.SquareN(x60, 60, x120);
- Curve25519Field.Multiply(x120, x60, x120);
- uint[] x131 = x60;
- Curve25519Field.SquareN(x120, 11, x131);
- Curve25519Field.Multiply(x131, x11, x131);
- uint[] x251 = x11;
- Curve25519Field.SquareN(x131, 120, x251);
- Curve25519Field.Multiply(x251, x120, x251);
- uint[] t1 = x251;
- Curve25519Field.Square(t1, t1);
- uint[] t2 = x120;
- Curve25519Field.Square(t1, t2);
- if (Nat256.Eq(x1, t2))
- {
- return new Curve25519FieldElement(t1);
- }
- /*
- * If the first guess is incorrect, we multiply by a precomputed power of 2 to get the second guess,
- * which is ((4x)^(m + 1))/2 mod Q
- */
- Curve25519Field.Multiply(t1, PRECOMP_POW2, t1);
- Curve25519Field.Square(t1, t2);
- if (Nat256.Eq(x1, t2))
- {
- return new Curve25519FieldElement(t1);
- }
- return null;
- }
- public override bool Equals(object obj)
- {
- return Equals(obj as Curve25519FieldElement);
- }
- public override bool Equals(ECFieldElement other)
- {
- return Equals(other as Curve25519FieldElement);
- }
- public virtual bool Equals(Curve25519FieldElement other)
- {
- if (this == other)
- return true;
- if (null == other)
- return false;
- return Nat256.Eq(x, other.x);
- }
- public override int GetHashCode()
- {
- return Q.GetHashCode() ^ Arrays.GetHashCode(x, 0, 8);
- }
- }
- }
- #endif
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