org.bouncycastle.jce.spec.ECNamedCurveSpec.java Source code

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Here is the source code for org.bouncycastle.jce.spec.ECNamedCurveSpec.java

Source

package org.bouncycastle.jce.spec;

import java.math.BigInteger;
import java.security.spec.ECField;
import java.security.spec.ECFieldF2m;
import java.security.spec.ECFieldFp;
import java.security.spec.ECPoint;
import java.security.spec.EllipticCurve;

import org.bouncycastle.jcajce.provider.asymmetric.util.EC5Util;
import org.bouncycastle.math.ec.ECAlgorithms;
import org.bouncycastle.math.ec.ECCurve;
import org.bouncycastle.math.field.FiniteField;
import org.bouncycastle.math.field.Polynomial;
import org.bouncycastle.math.field.PolynomialExtensionField;
import org.bouncycastle.util.Arrays;

/**
 * specification signifying that the curve parameters can also be
 * referred to by name.
 */
public class ECNamedCurveSpec extends java.security.spec.ECParameterSpec {
    private String name;

    private static EllipticCurve convertCurve(ECCurve curve, byte[] seed) {
        ECField field = convertField(curve.getField());
        BigInteger a = curve.getA().toBigInteger(), b = curve.getB().toBigInteger();
        return new EllipticCurve(field, a, b, seed);
    }

    private static ECField convertField(FiniteField field) {
        if (ECAlgorithms.isFpField(field)) {
            return new ECFieldFp(field.getCharacteristic());
        } else //if (ECAlgorithms.isF2mField(curveField))
        {
            Polynomial poly = ((PolynomialExtensionField) field).getMinimalPolynomial();
            int[] exponents = poly.getExponentsPresent();
            int[] ks = Arrays.reverse(Arrays.copyOfRange(exponents, 1, exponents.length - 1));
            return new ECFieldF2m(poly.getDegree(), ks);
        }
    }

    public ECNamedCurveSpec(String name, ECCurve curve, org.bouncycastle.math.ec.ECPoint g, BigInteger n) {
        super(convertCurve(curve, null), EC5Util.convertPoint(g), n, 1);

        this.name = name;
    }

    public ECNamedCurveSpec(String name, EllipticCurve curve, ECPoint g, BigInteger n) {
        super(curve, g, n, 1);

        this.name = name;
    }

    public ECNamedCurveSpec(String name, ECCurve curve, org.bouncycastle.math.ec.ECPoint g, BigInteger n,
            BigInteger h) {
        super(convertCurve(curve, null), EC5Util.convertPoint(g), n, h.intValue());

        this.name = name;
    }

    public ECNamedCurveSpec(String name, EllipticCurve curve, ECPoint g, BigInteger n, BigInteger h) {
        super(curve, g, n, h.intValue());

        this.name = name;
    }

    public ECNamedCurveSpec(String name, ECCurve curve, org.bouncycastle.math.ec.ECPoint g, BigInteger n,
            BigInteger h, byte[] seed) {
        super(convertCurve(curve, seed), EC5Util.convertPoint(g), n, h.intValue());

        this.name = name;
    }

    /**
     * return the name of the curve the EC domain parameters belong to.
     */
    public String getName() {
        return name;
    }
}