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using System;
using Org.BouncyCastle.Math.Raw;
using Org.BouncyCastle.Utilities.Encoders;
namespace Org.BouncyCastle.Math.EC.Custom.Djb
{
internal class Curve25519
: AbstractFpCurve
{
public static readonly BigInteger q = Curve25519FieldElement.Q;
private static readonly BigInteger C_a = new BigInteger(1, Hex.Decode("2AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA984914A144"));
private static readonly BigInteger C_b = new BigInteger(1, Hex.Decode("7B425ED097B425ED097B425ED097B425ED097B425ED097B4260B5E9C7710C864"));
private const int CURVE25519_DEFAULT_COORDS = COORD_JACOBIAN_MODIFIED;
private const int CURVE25519_FE_INTS = 8;
private static readonly ECFieldElement[] CURVE25519_AFFINE_ZS = new ECFieldElement[] {
new Curve25519FieldElement(BigInteger.One), new Curve25519FieldElement(C_a) };
protected readonly Curve25519Point m_infinity;
public Curve25519()
: base(q)
{
this.m_infinity = new Curve25519Point(this, null, null);
this.m_a = FromBigInteger(C_a);
this.m_b = FromBigInteger(C_b);
this.m_order = new BigInteger(1, Hex.Decode("1000000000000000000000000000000014DEF9DEA2F79CD65812631A5CF5D3ED"));
this.m_cofactor = BigInteger.ValueOf(8);
this.m_coord = CURVE25519_DEFAULT_COORDS;
}
protected override ECCurve CloneCurve()
{
return new Curve25519();
}
public override bool SupportsCoordinateSystem(int coord)
{
switch (coord)
{
case COORD_JACOBIAN_MODIFIED:
return true;
default:
return false;
}
}
public virtual BigInteger Q
{
get { return q; }
}
public override ECPoint Infinity
{
get { return m_infinity; }
}
public override int FieldSize
{
get { return q.BitLength; }
}
public override ECFieldElement FromBigInteger(BigInteger x)
{
return new Curve25519FieldElement(x);
}
protected internal override ECPoint CreateRawPoint(ECFieldElement x, ECFieldElement y, bool withCompression)
{
return new Curve25519Point(this, x, y, withCompression);
}
protected internal override ECPoint CreateRawPoint(ECFieldElement x, ECFieldElement y, ECFieldElement[] zs, bool withCompression)
{
return new Curve25519Point(this, x, y, zs, withCompression);
}
public override ECLookupTable CreateCacheSafeLookupTable(ECPoint[] points, int off, int len)
{
uint[] table = new uint[len * CURVE25519_FE_INTS * 2];
{
int pos = 0;
for (int i = 0; i < len; ++i)
{
ECPoint p = points[off + i];
Nat256.Copy(((Curve25519FieldElement)p.RawXCoord).x, 0, table, pos); pos += CURVE25519_FE_INTS;
Nat256.Copy(((Curve25519FieldElement)p.RawYCoord).x, 0, table, pos); pos += CURVE25519_FE_INTS;
}
}
return new Curve25519LookupTable(this, table, len);
}
private class Curve25519LookupTable
: AbstractECLookupTable
{
private readonly Curve25519 m_outer;
private readonly uint[] m_table;
private readonly int m_size;
internal Curve25519LookupTable(Curve25519 outer, uint[] table, int size)
{
this.m_outer = outer;
this.m_table = table;
this.m_size = size;
}
public override int Size
{
get { return m_size; }
}
public override ECPoint Lookup(int index)
{
uint[] x = Nat256.Create(), y = Nat256.Create();
int pos = 0;
for (int i = 0; i < m_size; ++i)
{
uint MASK = (uint)(((i ^ index) - 1) >> 31);
for (int j = 0; j < CURVE25519_FE_INTS; ++j)
{
x[j] ^= m_table[pos + j] & MASK;
y[j] ^= m_table[pos + CURVE25519_FE_INTS + j] & MASK;
}
pos += (CURVE25519_FE_INTS * 2);
}
return CreatePoint(x, y);
}
public override ECPoint LookupVar(int index)
{
uint[] x = Nat256.Create(), y = Nat256.Create();
int pos = index * CURVE25519_FE_INTS * 2;
for (int j = 0; j < CURVE25519_FE_INTS; ++j)
{
x[j] = m_table[pos + j];
y[j] = m_table[pos + CURVE25519_FE_INTS + j];
}
return CreatePoint(x, y);
}
private ECPoint CreatePoint(uint[] x, uint[] y)
{
return m_outer.CreateRawPoint(new Curve25519FieldElement(x), new Curve25519FieldElement(y), CURVE25519_AFFINE_ZS, false);
}
}
}
}
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