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The Bouncy Castle Java APIs for CMS, PKCS, EAC, TSP, CMP, CRMF, OCSP, and certificate generation. This jar contains APIs for JDK 1.5 and up. The APIs can be used in conjunction with a JCE/JCA provider such as the one provided with the Bouncy Castle Cryptography APIs.

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package org.bouncycastle.jce.provider;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.math.BigInteger;

import javax.crypto.interfaces.DHPublicKey;
import javax.crypto.spec.DHParameterSpec;
import javax.crypto.spec.DHPublicKeySpec;

import org.bouncycastle.asn1.ASN1Integer;
import org.bouncycastle.asn1.oiw.ElGamalParameter;
import org.bouncycastle.asn1.oiw.OIWObjectIdentifiers;
import org.bouncycastle.asn1.x509.AlgorithmIdentifier;
import org.bouncycastle.asn1.x509.SubjectPublicKeyInfo;
import org.bouncycastle.crypto.params.ElGamalPublicKeyParameters;
import org.bouncycastle.jcajce.provider.asymmetric.util.KeyUtil;
import org.bouncycastle.jce.interfaces.ElGamalPublicKey;
import org.bouncycastle.jce.spec.ElGamalParameterSpec;
import org.bouncycastle.jce.spec.ElGamalPublicKeySpec;

public class JCEElGamalPublicKey
    implements ElGamalPublicKey, DHPublicKey
{
    static final long serialVersionUID = 8712728417091216948L;
        
    private BigInteger              y;
    private ElGamalParameterSpec    elSpec;

    JCEElGamalPublicKey(
        ElGamalPublicKeySpec    spec)
    {
        this.y = spec.getY();
        this.elSpec = new ElGamalParameterSpec(spec.getParams().getP(), spec.getParams().getG());
    }

    JCEElGamalPublicKey(
        DHPublicKeySpec    spec)
    {
        this.y = spec.getY();
        this.elSpec = new ElGamalParameterSpec(spec.getP(), spec.getG());
    }
    
    JCEElGamalPublicKey(
        ElGamalPublicKey    key)
    {
        this.y = key.getY();
        this.elSpec = key.getParameters();
    }

    JCEElGamalPublicKey(
        DHPublicKey    key)
    {
        this.y = key.getY();
        this.elSpec = new ElGamalParameterSpec(key.getParams().getP(), key.getParams().getG());
    }
    
    JCEElGamalPublicKey(
        ElGamalPublicKeyParameters  params)
    {
        this.y = params.getY();
        this.elSpec = new ElGamalParameterSpec(params.getParameters().getP(), params.getParameters().getG());
    }

    JCEElGamalPublicKey(
        BigInteger              y,
        ElGamalParameterSpec    elSpec)
    {
        this.y = y;
        this.elSpec = elSpec;
    }

    JCEElGamalPublicKey(
        SubjectPublicKeyInfo    info)
    {
        ElGamalParameter        params = ElGamalParameter.getInstance(info.getAlgorithm().getParameters());
        ASN1Integer              derY = null;

        try
        {
            derY = (ASN1Integer)info.parsePublicKey();
        }
        catch (IOException e)
        {
            throw new IllegalArgumentException("invalid info structure in DSA public key");
        }

        this.y = derY.getValue();
        this.elSpec = new ElGamalParameterSpec(params.getP(), params.getG());
    }

    public String getAlgorithm()
    {
        return "ElGamal";
    }

    public String getFormat()
    {
        return "X.509";
    }

    public byte[] getEncoded()
    {
        return KeyUtil.getEncodedSubjectPublicKeyInfo(new AlgorithmIdentifier(OIWObjectIdentifiers.elGamalAlgorithm, new ElGamalParameter(elSpec.getP(), elSpec.getG())), new ASN1Integer(y));
    }

    public ElGamalParameterSpec getParameters()
    {
        return elSpec;
    }
    
    public DHParameterSpec getParams()
    {
        return new DHParameterSpec(elSpec.getP(), elSpec.getG());
    }

    public BigInteger getY()
    {
        return y;
    }

    private void readObject(
        ObjectInputStream   in)
        throws IOException, ClassNotFoundException
    {
        this.y = (BigInteger)in.readObject();
        this.elSpec = new ElGamalParameterSpec((BigInteger)in.readObject(), (BigInteger)in.readObject());
    }

    private void writeObject(
        ObjectOutputStream  out)
        throws IOException
    {
        out.writeObject(this.getY());
        out.writeObject(elSpec.getP());
        out.writeObject(elSpec.getG());
    }
}




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