/// <inheritdoc />
public bool IsPotentialElement(ECPoint element)
{
using (var ctx = BigNumberContextHandle.Create())
{
return(ECPointHandle.IsOnCurve(Handle, element.Handle, ctx));
}
}
public void TestAdd()
{
var algebra = new EllipticCurveAlgebra(EllipticCurveID.Prime256v1);
var generator = algebra.Generator;
var groupHandle = ECGroupHandle.CreateByCurveNID((int)EllipticCurveID.Prime256v1);
var ctx = BigNumberContextHandle.Create();
var kA = new BigInteger(27);
var kB = new BigInteger(13);
var pointA = new ECPoint(groupHandle);
ECPointHandle.Multiply(groupHandle, pointA.Handle, new BigNumber(kA).Handle, ECPointHandle.Null, BigNumberHandle.Null, ctx);
var pointB = new ECPoint(groupHandle);
ECPointHandle.Multiply(groupHandle, pointB.Handle, new BigNumber(kB).Handle, ECPointHandle.Null, BigNumberHandle.Null, ctx);
var expected = new ECPoint(groupHandle);
ECPointHandle.Multiply(groupHandle, expected.Handle, new BigNumber(kA + kB).Handle, ECPointHandle.Null, BigNumberHandle.Null, ctx);
var result = algebra.Add(pointA, pointB);
Assert.That(result.Equals(expected));
}
/// <inheritdoc />
public ECPoint Negate(ECPoint element)
{
using (var ctx = BigNumberContextHandle.Create())
{
var p = new ECPoint(Handle, element.Handle);
ECPointHandle.InvertInPlace(Handle, p.Handle, ctx);
return(p);
}
}
/// <inheritdoc />
public ECPoint Add(ECPoint left, ECPoint right)
{
using (var ctx = BigNumberContextHandle.Create())
{
var res = new ECPoint(Handle);
ECPointHandle.Add(Handle, res.Handle, left.Handle, right.Handle, ctx);
return(res);
}
}
/// <summary>
/// Multiplies this <see cref="BigNumber" /> with <paramref name="other"/>
/// modulo <paramref name="modulo"/> and returns the result.
///
/// Precisely, the returned value is <c>z = x * y % m</c>, where
/// <c>x</c> is the value of this <see cref="BigNumber" /> instance,
/// <c>y</c> the value of <paramref name="other"/> and <c>m</c> the
/// value of <paramref name="modulo"/>.
/// </summary>
/// <param name="other">The number with which to multiply.</param>
/// <param name="modulo">The modulo for the multiplication.</param>
/// <returns>
/// A <see cref="BigNumber" /> instance with value<c>z</c>.
/// </returns>
public BigNumber ModMul(BigNumber other, BigNumber modulo)
{
using (var ctx = BigNumberContextHandle.Create())
{
var result = new BigNumber();
BigNumberHandle.ModMul(result.Handle, Handle, other.Handle, modulo.Handle, ctx);
return(result);
}
}
/// <summary>
/// Decodes a <see cref="ECPoint" /> instance from a byte buffer.
/// </summary>
/// <param name="ecGroupHandle">Native handle for the group the point lies on.</param>
/// <param name="buffer">Byte array containing an encoding of the curve point.</param>
/// <returns><see cref="ECPoint" /> instance of the point encoded in the buffer.</returns>
internal static ECPoint CreateFromBytes(ECGroupHandle ecGroupHandle, byte[] buffer)
{
using (var ctx = BigNumberContextHandle.Create())
{
var point = new ECPoint(ecGroupHandle);
ECPointHandle.FromByteBuffer(point._ecGroup, point.Handle, buffer, ctx);
return(point);
}
}
/// <summary>
/// Creates a new <see cref="EllipticCurveAlgebra" /> instance
/// for the curve identified by <paramref name="curveId"/>.
/// </summary>
/// <param name="curveId">Identifier of the elliptic curve.</param>
public EllipticCurveAlgebra(EllipticCurveID curveId)
{
Handle = ECGroupHandle.CreateByCurveNID((int)curveId);
using (var ctx = BigNumberContextHandle.Create())
{
ECGroupHandle.PrecomputeGeneratorMultiples(Handle, ctx);
}
}
/// <summary>
/// Encodes the curve point in a byte buffer.
/// </summary>
/// <param name="encoding">The encoding scheme used to encode the point in the buffer.</param>
/// <returns>Byte buffer containing the encoded curve point.</returns>
public byte[] ToBytes(PointEncoding encoding = PointEncoding.Compressed)
{
using (var ctx = BigNumberContextHandle.Create())
{
int requiredBufferLength = ECPointHandle.ToByteBuffer(_ecGroup, Handle, encoding, null, ctx);
byte[] buffer = new byte[requiredBufferLength];
int writtenBytes = ECPointHandle.ToByteBuffer(_ecGroup, Handle, encoding, buffer, ctx);
Debug.Assert(writtenBytes == requiredBufferLength);
return(buffer);
}
}
/// <inheritdoc />
public override bool Equals(object?obj)
{
EllipticCurveAlgebra?other = obj as EllipticCurveAlgebra;
if (other == null)
{
return(false);
}
using (var ctx = BigNumberContextHandle.Create())
{
return(ECGroupHandle.Compare(this.Handle, other.Handle, ctx));
}
}
/// <summary>
/// Returns the affine coordinates of the curve point.
/// </summary>
/// <returns>Tuple containing x- and y-coordinate.</returns>
public (BigNumber, BigNumber) GetCoordinates()
{
if (IsAtInfinity)
{
throw new InvalidOperationException("Cannot get coordinates from point at infinity!");
}
using (var ctx = BigNumberContextHandle.Create())
{
var x = new BigNumber();
var y = new BigNumber();
ECPointHandle.GetAffineCoordinates(_ecGroup, Handle, x.Handle, y.Handle, ctx);
return(x, y);
}
}
/// <inheritdoc />
public override bool Equals(object?obj)
{
ECPoint?other = obj as ECPoint;
if (other == null)
{
return(false);
}
using (var ctx = BigNumberContextHandle.Create())
{
return(ECPointHandle.Compare(_ecGroup, this.Handle, other.Handle, ctx));
}
}
public void TestIsElement()
{
var algebra = new EllipticCurveAlgebra(EllipticCurveID.Prime256v1);
var groupHandle = algebra.Handle;
var ctx = BigNumberContextHandle.Create();
var index = new BigInteger(3);
var point = new ECPoint(groupHandle);
ECPointHandle.Multiply(groupHandle, point.Handle, new BigNumber(index).Handle, ECPointHandle.Null, BigNumberHandle.Null, ctx);
Assert.That(algebra.IsPotentialElement(point), "valid point not accepted by IsPotentialElement!");
Assert.That(algebra.IsSafeElement(point), "valid point not accepted by IsSafeElement!");
}
public void TestFromToBytes()
{
var algebra = new EllipticCurveAlgebra(EllipticCurveID.Prime256v1);
var generator = algebra.Generator;
var groupHandle = ECGroupHandle.CreateByCurveNID((int)EllipticCurveID.Prime256v1);
var ctx = BigNumberContextHandle.Create();
var index = new BigInteger(3);
var point = new ECPoint(groupHandle);
ECPointHandle.Multiply(groupHandle, point.Handle, new BigNumber(index).Handle, ECPointHandle.Null, BigNumberHandle.Null, ctx);
byte[] buffer = algebra.ToBytes(point);
var result = algebra.FromBytes(buffer);
Assert.That(result.Equals(point));
}
public void TestGenerateElement()
{
var algebra = new EllipticCurveAlgebra(EllipticCurveID.Prime256v1);
var generator = algebra.Generator;
var groupHandle = ECGroupHandle.CreateByCurveNID((int)EllipticCurveID.Prime256v1);
var ctx = BigNumberContextHandle.Create();
var index = SecureBigNumber.FromBigNumber(new BigNumber(
BigInteger.Parse("97752369786356789875745735", System.Globalization.NumberStyles.Integer)
));
var expected = new ECPoint(groupHandle);
ECPointHandle.Multiply(groupHandle, expected.Handle, index.Handle, ECPointHandle.Null, BigNumberHandle.Null, ctx);
var result = algebra.GenerateElement(index);
Assert.That(result.Equals(expected));
}
public void TestNegate()
{
var algebra = new EllipticCurveAlgebra(EllipticCurveID.Prime256v1);
var generator = algebra.Generator;
var groupHandle = ECGroupHandle.CreateByCurveNID((int)EllipticCurveID.Prime256v1);
var ctx = BigNumberContextHandle.Create();
var index = new BigInteger(3);
var point = new ECPoint(groupHandle);
ECPointHandle.Multiply(groupHandle, point.Handle, new BigNumber(index).Handle, ECPointHandle.Null, BigNumberHandle.Null, ctx);
var result = algebra.Negate(point);
var pointPlusNegated = algebra.Add(point, result);
Assert.That(pointPlusNegated.Equals(algebra.NeutralElement));
}
public void TestMultipy()
{
var algebra = new EllipticCurveAlgebra(EllipticCurveID.Prime256v1);
var generator = algebra.Generator;
var groupHandle = ECGroupHandle.CreateByCurveNID((int)EllipticCurveID.Prime256v1);
var ctx = BigNumberContextHandle.Create();
var factor = SecureBigNumber.FromBigNumber(new BigNumber(13));
var basePointFactor = new BigInteger(27);
var point = new ECPoint(groupHandle);
ECPointHandle.Multiply(groupHandle, point.Handle, new BigNumber(basePointFactor).Handle, ECPointHandle.Null, BigNumberHandle.Null, ctx);
var expected = new ECPoint(groupHandle);
ECPointHandle.Multiply(groupHandle, expected.Handle, BigNumberHandle.Null, point.Handle, factor.Handle, ctx);
var result = algebra.MultiplyScalar(point, factor);
Assert.That(result.Equals(expected));
}
public void SetUp()
{
groupHandle = ECGroupHandle.CreateByCurveNID((int)EllipticCurveID.Prime256v1);
rawPointHandle = ECGroupHandle.GetGenerator(groupHandle);
ctx = BigNumberContextHandle.Create();
}