org.bouncycastle.math.ec.custom.sec.SecP256K1Curve Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of bcprov-ext-debug-jdk18on Show documentation
The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for Java 1.8 and later with debug enabled.
The newest version!
package org.bouncycastle.math.ec.custom.sec;

import java.math.BigInteger;
import java.security.SecureRandom;

import org.bouncycastle.math.ec.AbstractECLookupTable;
import org.bouncycastle.math.ec.ECConstants;
import org.bouncycastle.math.ec.ECCurve;
import org.bouncycastle.math.ec.ECFieldElement;
import org.bouncycastle.math.ec.ECLookupTable;
import org.bouncycastle.math.ec.ECPoint;
import org.bouncycastle.math.raw.Nat256;
import org.bouncycastle.util.encoders.Hex;

public class SecP256K1Curve extends ECCurve.AbstractFp
{
    public static final BigInteger q = SecP256K1FieldElement.Q;

    private static final int SECP256K1_DEFAULT_COORDS = COORD_JACOBIAN;
    private static final ECFieldElement[] SECP256K1_AFFINE_ZS = new ECFieldElement[] { new SecP256K1FieldElement(ECConstants.ONE) }; 

    protected SecP256K1Point infinity;

    public SecP256K1Curve()
    {
        super(q);

        this.infinity = new SecP256K1Point(this, null, null);

        this.a = fromBigInteger(ECConstants.ZERO);
        this.b = fromBigInteger(BigInteger.valueOf(7));
        this.order = new BigInteger(1, Hex.decodeStrict("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141"));
        this.cofactor = BigInteger.valueOf(1);
        this.coord = SECP256K1_DEFAULT_COORDS;
    }

    protected ECCurve cloneCurve()
    {
        return new SecP256K1Curve();
    }

    public boolean supportsCoordinateSystem(int coord)
    {
        switch (coord)
        {
        case COORD_JACOBIAN:
            return true;
        default:
            return false;
        }
    }

    public BigInteger getQ()
    {
        return q;
    }

    public int getFieldSize()
    {
        return q.bitLength();
    }

    public ECFieldElement fromBigInteger(BigInteger x)
    {
        return new SecP256K1FieldElement(x);
    }

    protected ECPoint createRawPoint(ECFieldElement x, ECFieldElement y)
    {
        return new SecP256K1Point(this, x, y);
    }

    protected ECPoint createRawPoint(ECFieldElement x, ECFieldElement y, ECFieldElement[] zs)
    {
        return new SecP256K1Point(this, x, y, zs);
    }

    public ECPoint getInfinity()
    {
        return infinity;
    }

    public ECLookupTable createCacheSafeLookupTable(ECPoint[] points, int off, final int len)
    {
        final int FE_INTS = 8;

        final int[] table = new int[len * FE_INTS * 2];
        {
            int pos = 0;
            for (int i = 0; i < len; ++i)
            {
                ECPoint p = points[off + i];
                Nat256.copy(((SecP256K1FieldElement)p.getRawXCoord()).x, 0, table, pos); pos += FE_INTS;
                Nat256.copy(((SecP256K1FieldElement)p.getRawYCoord()).x, 0, table, pos); pos += FE_INTS;
            }
        }

        return new AbstractECLookupTable()
        {
            public int getSize()
            {
                return len;
            }

            public ECPoint lookup(int index)
            {
                int[] x = Nat256.create(), y = Nat256.create();
                int pos = 0;

                for (int i = 0; i < len; ++i)
                {
                    int MASK = ((i ^ index) - 1) >> 31;

                    for (int j = 0; j < FE_INTS; ++j)
                    {
                        x[j] ^= table[pos + j] & MASK;
                        y[j] ^= table[pos + FE_INTS + j] & MASK;
                    }

                    pos += (FE_INTS * 2);
                }

                return createPoint(x, y);
            }

            public ECPoint lookupVar(int index)
            {
                int[] x = Nat256.create(), y = Nat256.create();
                int pos = index * FE_INTS * 2;

                for (int j = 0; j < FE_INTS; ++j)
                {
                    x[j] = table[pos + j];
                    y[j] = table[pos + FE_INTS + j];
                }

                return createPoint(x, y);
            }

            private ECPoint createPoint(int[] x, int[] y)
            {
                return createRawPoint(new SecP256K1FieldElement(x), new SecP256K1FieldElement(y), SECP256K1_AFFINE_ZS);
            }
        };
    }

    public ECFieldElement randomFieldElement(SecureRandom r)
    {
        int[] x = Nat256.create();
        SecP256K1Field.random(r, x);
        return new SecP256K1FieldElement(x);
    }

    public ECFieldElement randomFieldElementMult(SecureRandom r)
    {
        int[] x = Nat256.create();
        SecP256K1Field.randomMult(r, x);
        return new SecP256K1FieldElement(x);
    }
}