package org.bouncycastle.jce;

import java.security.spec.ECFieldF2m;
import java.security.spec.ECFieldFp;
import java.security.spec.ECPoint;
import java.security.spec.EllipticCurve;

import org.bouncycastle.math.ec.ECCurve;

Utility class for handling EC point decoding.
/** * Utility class for handling EC point decoding. */
public class ECPointUtil {
Decode a point on this curve which has been encoded using point compression (X9.62 s 4.2.1 and 4.2.2) or regular encoding.
Params:
  • curve – The elliptic curve.
  • encoded – The encoded point.
Returns:the decoded point.
/** * Decode a point on this curve which has been encoded using point * compression (X9.62 s 4.2.1 and 4.2.2) or regular encoding. * * @param curve * The elliptic curve. * @param encoded * The encoded point. * @return the decoded point. */
public static ECPoint decodePoint( EllipticCurve curve, byte[] encoded) { ECCurve c = null; if (curve.getField() instanceof ECFieldFp) { c = new ECCurve.Fp( ((ECFieldFp)curve.getField()).getP(), curve.getA(), curve.getB()); } else { int k[] = ((ECFieldF2m)curve.getField()).getMidTermsOfReductionPolynomial(); if (k.length == 3) { c = new ECCurve.F2m( ((ECFieldF2m)curve.getField()).getM(), k[2], k[1], k[0], curve.getA(), curve.getB()); } else { c = new ECCurve.F2m( ((ECFieldF2m)curve.getField()).getM(), k[0], curve.getA(), curve.getB()); } } org.bouncycastle.math.ec.ECPoint p = c.decodePoint(encoded); return new ECPoint(p.getX().toBigInteger(), p.getY().toBigInteger()); } }