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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.

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package org.bouncycastle.jcajce.provider.asymmetric.ec;

import java.math.BigInteger;
import java.security.InvalidKeyException;
import java.security.PublicKey;
import java.security.spec.ECGenParameterSpec;
import java.security.spec.ECParameterSpec;

import org.bouncycastle.asn1.ASN1ObjectIdentifier;
import org.bouncycastle.asn1.DERNull;
import org.bouncycastle.asn1.x9.X962Parameters;
import org.bouncycastle.asn1.x9.X9ECParameters;
import org.bouncycastle.asn1.x9.X9ECPoint;
import org.bouncycastle.crypto.params.AsymmetricKeyParameter;
import org.bouncycastle.jcajce.provider.asymmetric.util.EC5Util;
import org.bouncycastle.jcajce.provider.asymmetric.util.ECUtil;
import org.bouncycastle.jce.spec.ECNamedCurveSpec;
import org.bouncycastle.math.ec.ECCurve;

class ECUtils
{
    static AsymmetricKeyParameter generatePublicKeyParameter(
            PublicKey key)
        throws InvalidKeyException
    {
        return (key instanceof BCECPublicKey) ? ((BCECPublicKey)key).engineGetKeyParameters() : ECUtil.generatePublicKeyParameter(key);
    }

    static X9ECParameters getDomainParametersFromGenSpec(ECGenParameterSpec genSpec)
    {
        return getDomainParametersFromName(genSpec.getName());
    }

    static X9ECParameters getDomainParametersFromName(String curveName)
    {
        X9ECParameters domainParameters;
        try
        {
            if (curveName.charAt(0) >= '0' && curveName.charAt(0) <= '2')
            {
                ASN1ObjectIdentifier oidID = new ASN1ObjectIdentifier(curveName);
                domainParameters = ECUtil.getNamedCurveByOid(oidID);
            }
            else
            {
                if (curveName.indexOf(' ') > 0)
                {
                    curveName = curveName.substring(curveName.indexOf(' ') + 1);
                    domainParameters = ECUtil.getNamedCurveByName(curveName);
                }
                else
                {
                    domainParameters = ECUtil.getNamedCurveByName(curveName);
                }
            }
        }
        catch (IllegalArgumentException ex)
        {
            domainParameters = ECUtil.getNamedCurveByName(curveName);
        }
        return domainParameters;
    }

    static X962Parameters getDomainParametersFromName(ECParameterSpec ecSpec, boolean withCompression)
    {
        X962Parameters params;

        if (ecSpec instanceof ECNamedCurveSpec)
        {
            ASN1ObjectIdentifier curveOid = ECUtil.getNamedCurveOid(((ECNamedCurveSpec)ecSpec).getName());
            if (curveOid == null)
            {
                curveOid = new ASN1ObjectIdentifier(((ECNamedCurveSpec)ecSpec).getName());
            }
            params = new X962Parameters(curveOid);
        }
        else if (ecSpec == null)
        {
            params = new X962Parameters(DERNull.INSTANCE);
        }
        else
        {
            ECCurve curve = EC5Util.convertCurve(ecSpec.getCurve());

            X9ECParameters ecP = new X9ECParameters(
                curve,
                new X9ECPoint(EC5Util.convertPoint(curve, ecSpec.getGenerator()), withCompression),
                ecSpec.getOrder(),
                BigInteger.valueOf(ecSpec.getCofactor()),
                ecSpec.getCurve().getSeed());

            params = new X962Parameters(ecP);
        }

        return params;
    }
}