public override ECPoint Add(ECPoint b) { if (this.IsInfinity) { return(b); } if (b.IsInfinity) { return(this); } if (this == b) { return(Twice()); } ECCurve curve = this.Curve; SecP192R1FieldElement X1 = (SecP192R1FieldElement)this.RawXCoord, Y1 = (SecP192R1FieldElement)this.RawYCoord; SecP192R1FieldElement X2 = (SecP192R1FieldElement)b.RawXCoord, Y2 = (SecP192R1FieldElement)b.RawYCoord; SecP192R1FieldElement Z1 = (SecP192R1FieldElement)this.RawZCoords[0]; SecP192R1FieldElement Z2 = (SecP192R1FieldElement)b.RawZCoords[0]; uint[] tt1 = Nat192.CreateExt(); uint[] tt2 = Nat192.CreateExt(); uint[] t3 = Nat192.Create(); uint[] t4 = Nat192.Create(); bool Z1IsOne = Z1.IsOne; uint[] U2, S2; if (Z1IsOne) { U2 = X2.x; S2 = Y2.x; } else { S2 = t3; SecP192R1Field.Square(Z1.x, S2); U2 = tt2; SecP192R1Field.Multiply(S2, X2.x, U2); SecP192R1Field.Multiply(S2, Z1.x, S2); SecP192R1Field.Multiply(S2, Y2.x, S2); } bool Z2IsOne = Z2.IsOne; uint[] U1, S1; if (Z2IsOne) { U1 = X1.x; S1 = Y1.x; } else { S1 = t4; SecP192R1Field.Square(Z2.x, S1); U1 = tt1; SecP192R1Field.Multiply(S1, X1.x, U1); SecP192R1Field.Multiply(S1, Z2.x, S1); SecP192R1Field.Multiply(S1, Y1.x, S1); } uint[] H = Nat192.Create(); SecP192R1Field.Subtract(U1, U2, H); uint[] R = tt2; SecP192R1Field.Subtract(S1, S2, R); // Check if b == this or b == -this if (Nat192.IsZero(H)) { if (Nat192.IsZero(R)) { // this == b, i.e. this must be doubled return(this.Twice()); } // this == -b, i.e. the result is the point at infinity return(curve.Infinity); } uint[] HSquared = t3; SecP192R1Field.Square(H, HSquared); uint[] G = Nat192.Create(); SecP192R1Field.Multiply(HSquared, H, G); uint[] V = t3; SecP192R1Field.Multiply(HSquared, U1, V); Nat192.Mul(S1, G, tt1); SecP192R1FieldElement X3 = new SecP192R1FieldElement(t4); SecP192R1Field.Square(R, X3.x); SecP192R1Field.Add(X3.x, G, X3.x); SecP192R1Field.Subtract(X3.x, V, X3.x); SecP192R1Field.Subtract(X3.x, V, X3.x); SecP192R1FieldElement Y3 = new SecP192R1FieldElement(G); SecP192R1Field.Subtract(V, X3.x, Y3.x); Nat192.Mul(Y3.x, R, tt2); SecP192R1Field.SubtractExt(tt2, tt1, tt2); SecP192R1Field.Reduce(tt2, Y3.x); SecP192R1FieldElement Z3 = new SecP192R1FieldElement(H); if (!Z1IsOne) { SecP192R1Field.Multiply(Z3.x, Z1.x, Z3.x); } if (!Z2IsOne) { SecP192R1Field.Multiply(Z3.x, Z2.x, Z3.x); } ECFieldElement[] zs = new ECFieldElement[] { Z3 }; return(new SecP192R1Point(curve, X3, Y3, zs, IsCompressed)); }