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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 JDK 1.5 and up.
package org.bouncycastle.math.ec;
import java.math.BigInteger;
import org.bouncycastle.math.ec.endo.EndoUtil;
import org.bouncycastle.math.ec.endo.GLVEndomorphism;
public class GLVMultiplier extends AbstractECMultiplier
{
protected final ECCurve curve;
protected final GLVEndomorphism glvEndomorphism;
public GLVMultiplier(ECCurve curve, GLVEndomorphism glvEndomorphism)
{
if (curve == null || curve.getOrder() == null)
{
throw new IllegalArgumentException("Need curve with known group order");
}
this.curve = curve;
this.glvEndomorphism = glvEndomorphism;
}
protected ECPoint multiplyPositive(ECPoint p, BigInteger k)
{
if (!curve.equals(p.getCurve()))
{
throw new IllegalStateException();
}
BigInteger n = p.getCurve().getOrder();
BigInteger[] ab = glvEndomorphism.decomposeScalar(k.mod(n));
BigInteger a = ab[0], b = ab[1];
if (glvEndomorphism.hasEfficientPointMap())
{
return ECAlgorithms.implShamirsTrickWNaf(glvEndomorphism, p, a, b);
}
ECPoint q = EndoUtil.mapPoint(glvEndomorphism, p);
return ECAlgorithms.implShamirsTrickWNaf(p, a, q, b);
}
}