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.
*/
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.
*
* @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());
}
}