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280 lines
8.5 KiB
280 lines
8.5 KiB
2 months ago
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using System;
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using Org.BouncyCastle.Math.Raw;
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namespace Org.BouncyCastle.Math.EC.Custom.Sec
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{
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internal class SecP256R1Point
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: AbstractFpPoint
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{
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/**
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* Create a point which encodes with point compression.
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*
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* @param curve
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* the curve to use
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* @param x
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* affine x co-ordinate
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* @param y
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* affine y co-ordinate
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*
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* @deprecated Use ECCurve.createPoint to construct points
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*/
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public SecP256R1Point(ECCurve curve, ECFieldElement x, ECFieldElement y)
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: this(curve, x, y, false)
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{
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}
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/**
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* Create a point that encodes with or without point compresion.
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*
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* @param curve
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* the curve to use
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* @param x
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* affine x co-ordinate
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* @param y
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* affine y co-ordinate
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* @param withCompression
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* if true encode with point compression
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*
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* @deprecated per-point compression property will be removed, refer
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* {@link #getEncoded(bool)}
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*/
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public SecP256R1Point(ECCurve curve, ECFieldElement x, ECFieldElement y, bool withCompression)
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: base(curve, x, y, withCompression)
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{
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if ((x == null) != (y == null))
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throw new ArgumentException("Exactly one of the field elements is null");
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}
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internal SecP256R1Point(ECCurve curve, ECFieldElement x, ECFieldElement y, ECFieldElement[] zs, bool withCompression)
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: base(curve, x, y, zs, withCompression)
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{
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}
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protected override ECPoint Detach()
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{
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return new SecP256R1Point(null, AffineXCoord, AffineYCoord);
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}
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public override ECPoint Add(ECPoint b)
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{
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if (this.IsInfinity)
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return b;
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if (b.IsInfinity)
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return this;
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if (this == b)
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return Twice();
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ECCurve curve = this.Curve;
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SecP256R1FieldElement X1 = (SecP256R1FieldElement)this.RawXCoord, Y1 = (SecP256R1FieldElement)this.RawYCoord;
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SecP256R1FieldElement X2 = (SecP256R1FieldElement)b.RawXCoord, Y2 = (SecP256R1FieldElement)b.RawYCoord;
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SecP256R1FieldElement Z1 = (SecP256R1FieldElement)this.RawZCoords[0];
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SecP256R1FieldElement Z2 = (SecP256R1FieldElement)b.RawZCoords[0];
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uint c;
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uint[] tt1 = Nat256.CreateExt();
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uint[] t2 = Nat256.Create();
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uint[] t3 = Nat256.Create();
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uint[] t4 = Nat256.Create();
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bool Z1IsOne = Z1.IsOne;
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uint[] U2, S2;
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if (Z1IsOne)
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{
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U2 = X2.x;
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S2 = Y2.x;
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}
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else
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{
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S2 = t3;
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SecP256R1Field.Square(Z1.x, S2);
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U2 = t2;
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SecP256R1Field.Multiply(S2, X2.x, U2);
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SecP256R1Field.Multiply(S2, Z1.x, S2);
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SecP256R1Field.Multiply(S2, Y2.x, S2);
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}
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bool Z2IsOne = Z2.IsOne;
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uint[] U1, S1;
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if (Z2IsOne)
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{
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U1 = X1.x;
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S1 = Y1.x;
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}
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else
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{
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S1 = t4;
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SecP256R1Field.Square(Z2.x, S1);
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U1 = tt1;
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SecP256R1Field.Multiply(S1, X1.x, U1);
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SecP256R1Field.Multiply(S1, Z2.x, S1);
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SecP256R1Field.Multiply(S1, Y1.x, S1);
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}
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uint[] H = Nat256.Create();
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SecP256R1Field.Subtract(U1, U2, H);
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uint[] R = t2;
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SecP256R1Field.Subtract(S1, S2, R);
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// Check if b == this or b == -this
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if (Nat256.IsZero(H))
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{
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if (Nat256.IsZero(R))
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{
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// this == b, i.e. this must be doubled
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return this.Twice();
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}
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// this == -b, i.e. the result is the point at infinity
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return curve.Infinity;
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}
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uint[] HSquared = t3;
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SecP256R1Field.Square(H, HSquared);
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uint[] G = Nat256.Create();
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SecP256R1Field.Multiply(HSquared, H, G);
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uint[] V = t3;
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SecP256R1Field.Multiply(HSquared, U1, V);
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SecP256R1Field.Negate(G, G);
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Nat256.Mul(S1, G, tt1);
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c = Nat256.AddBothTo(V, V, G);
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SecP256R1Field.Reduce32(c, G);
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SecP256R1FieldElement X3 = new SecP256R1FieldElement(t4);
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SecP256R1Field.Square(R, X3.x);
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SecP256R1Field.Subtract(X3.x, G, X3.x);
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SecP256R1FieldElement Y3 = new SecP256R1FieldElement(G);
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SecP256R1Field.Subtract(V, X3.x, Y3.x);
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SecP256R1Field.MultiplyAddToExt(Y3.x, R, tt1);
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SecP256R1Field.Reduce(tt1, Y3.x);
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SecP256R1FieldElement Z3 = new SecP256R1FieldElement(H);
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if (!Z1IsOne)
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{
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SecP256R1Field.Multiply(Z3.x, Z1.x, Z3.x);
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}
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if (!Z2IsOne)
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{
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SecP256R1Field.Multiply(Z3.x, Z2.x, Z3.x);
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}
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ECFieldElement[] zs = new ECFieldElement[]{ Z3 };
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return new SecP256R1Point(curve, X3, Y3, zs, IsCompressed);
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}
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public override ECPoint Twice()
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{
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if (this.IsInfinity)
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return this;
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ECCurve curve = this.Curve;
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SecP256R1FieldElement Y1 = (SecP256R1FieldElement)this.RawYCoord;
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if (Y1.IsZero)
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return curve.Infinity;
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SecP256R1FieldElement X1 = (SecP256R1FieldElement)this.RawXCoord, Z1 = (SecP256R1FieldElement)this.RawZCoords[0];
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uint c;
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uint[] t1 = Nat256.Create();
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uint[] t2 = Nat256.Create();
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uint[] Y1Squared = Nat256.Create();
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SecP256R1Field.Square(Y1.x, Y1Squared);
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uint[] T = Nat256.Create();
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SecP256R1Field.Square(Y1Squared, T);
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bool Z1IsOne = Z1.IsOne;
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uint[] Z1Squared = Z1.x;
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if (!Z1IsOne)
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{
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Z1Squared = t2;
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SecP256R1Field.Square(Z1.x, Z1Squared);
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}
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SecP256R1Field.Subtract(X1.x, Z1Squared, t1);
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uint[] M = t2;
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SecP256R1Field.Add(X1.x, Z1Squared, M);
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SecP256R1Field.Multiply(M, t1, M);
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c = Nat256.AddBothTo(M, M, M);
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SecP256R1Field.Reduce32(c, M);
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uint[] S = Y1Squared;
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SecP256R1Field.Multiply(Y1Squared, X1.x, S);
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c = Nat.ShiftUpBits(8, S, 2, 0);
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SecP256R1Field.Reduce32(c, S);
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c = Nat.ShiftUpBits(8, T, 3, 0, t1);
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SecP256R1Field.Reduce32(c, t1);
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SecP256R1FieldElement X3 = new SecP256R1FieldElement(T);
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SecP256R1Field.Square(M, X3.x);
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SecP256R1Field.Subtract(X3.x, S, X3.x);
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SecP256R1Field.Subtract(X3.x, S, X3.x);
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SecP256R1FieldElement Y3 = new SecP256R1FieldElement(S);
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SecP256R1Field.Subtract(S, X3.x, Y3.x);
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SecP256R1Field.Multiply(Y3.x, M, Y3.x);
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SecP256R1Field.Subtract(Y3.x, t1, Y3.x);
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SecP256R1FieldElement Z3 = new SecP256R1FieldElement(M);
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SecP256R1Field.Twice(Y1.x, Z3.x);
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if (!Z1IsOne)
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{
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SecP256R1Field.Multiply(Z3.x, Z1.x, Z3.x);
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}
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return new SecP256R1Point(curve, X3, Y3, new ECFieldElement[]{ Z3 }, IsCompressed);
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}
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public override ECPoint TwicePlus(ECPoint b)
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{
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if (this == b)
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return ThreeTimes();
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if (this.IsInfinity)
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return b;
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if (b.IsInfinity)
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return Twice();
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ECFieldElement Y1 = this.RawYCoord;
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if (Y1.IsZero)
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return b;
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return Twice().Add(b);
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}
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public override ECPoint ThreeTimes()
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{
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if (this.IsInfinity || this.RawYCoord.IsZero)
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return this;
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// NOTE: Be careful about recursions between TwicePlus and ThreeTimes
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return Twice().Add(this);
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}
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public override ECPoint Negate()
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{
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if (IsInfinity)
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return this;
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return new SecP256R1Point(Curve, RawXCoord, RawYCoord.Negate(), RawZCoords, IsCompressed);
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}
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}
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}
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