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/* GnuDSAKeyPairGenerator.java --- Gnu DSA Key Pair Generator

   Copyright (C) 1999, 2005  Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation; either version 2, or (at your option)

any later version.

GNU Classpath is distributed in the hope that it will be useful, but

WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

General Public License for more details.

You should have received a copy of the GNU General Public License

along with GNU Classpath; see the file COPYING.  If not, write to the

Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

02110-1301 USA.

Linking this library statically or dynamically with other modules is

making a combined work based on this library.  Thus, the terms and

conditions of the GNU General Public License cover the whole

combination.

As a special exception, the copyright holders of this library give you

permission to link this library with independent modules to produce an

executable, regardless of the license terms of these independent

modules, and to copy and distribute the resulting executable under

terms of your choice, provided that you also meet, for each linked

independent module, the terms and conditions of the license of that

module.  An independent module is a module which is not derived from

or based on this library.  If you modify this library, you may extend

this exception to your version of the library, but you are not

obligated to do so.  If you do not wish to do so, delete this

exception statement from your version. */

package gnu.java.security.provider;

import java.math.BigInteger;

import java.security.AlgorithmParameterGenerator;

import java.security.AlgorithmParameters;

import java.security.InvalidAlgorithmParameterException;

import java.security.InvalidParameterException;

import java.security.KeyPair;

import java.security.KeyPairGeneratorSpi;

import java.security.NoSuchAlgorithmException;

import java.security.SecureRandom;

import java.security.interfaces.DSAParams;

import java.security.spec.AlgorithmParameterSpec;

import java.security.spec.DSAParameterSpec;

import java.security.spec.InvalidParameterSpecException;

import java.util.Random;

public class DSAKeyPairGenerator extends KeyPairGeneratorSpi

        implements java.security.interfaces.DSAKeyPairGenerator

{

int keysize;

SecureRandom random;

private BigInteger q = null; // the small prime

private BigInteger p = null; // the big prime

private BigInteger g = null;

public DSAKeyPairGenerator()

{

        keysize = 1024;

        getDefaults ();

}

public void initialize(int keysize, SecureRandom random)

{

        initialize (keysize, false, random);

}

public void initialize(AlgorithmParameterSpec params,

                       SecureRandom random)

                throws InvalidAlgorithmParameterException

{

        if( !( params instanceof DSAParameterSpec ) )

                throw new InvalidAlgorithmParameterException("Must be DSAParameterSpec");

        try

        {

                initialize ((DSAParams) params, random);

        }

        catch (InvalidParameterException ipe)

        {

                InvalidAlgorithmParameterException iape =

                        new InvalidAlgorithmParameterException();

                iape.initCause (ipe);

                throw iape;

        }

}

public void initialize (DSAParams params, SecureRandom random)

{

        DSAParameterSpec dsaparameterspec = (DSAParameterSpec)params;

        if (dsaparameterspec.getP() == null

            || dsaparameterspec.getQ() == null

            || dsaparameterspec.getG() == null)

        {

                throw new InvalidParameterException ("none of p, q, or g may be null");

        }

        p = dsaparameterspec.getP();

        q = dsaparameterspec.getQ();

        g = dsaparameterspec.getG();

        this.random = random;

}

public void initialize(int modlen, boolean genParams, SecureRandom random)

        throws InvalidParameterException

{

        if( ((modlen % 64) != 0) || (modlen < 512) || (modlen > 1024) )

                throw new InvalidParameterException();

        this.keysize = modlen;

        this.random = random;

        if (this.random == null)

        {

                this.random = new SecureRandom ();

        }

        if (genParams)

        {

                try

                {

                        AlgorithmParameterGenerator apgDSA = AlgorithmParameterGenerator.getInstance("DSA");

                        apgDSA.init (modlen, random);

                        AlgorithmParameters apDSA = apgDSA.generateParameters();

                        DSAParameterSpec dsaparameterspec = (DSAParameterSpec)apDSA.getParameterSpec( DSAParameterSpec.class );

                        p = dsaparameterspec.getP();

                        q = dsaparameterspec.getQ();

                        g = dsaparameterspec.getG();

                }

                catch (NoSuchAlgorithmException nsae)

                {

                        InvalidParameterException ipe =

                                new InvalidParameterException ("can't generate DSA parameters");

                        ipe.initCause (nsae);

                        throw ipe;

                }

                catch (InvalidParameterSpecException ipse)

                {

                        InvalidParameterException ipe =

                                new InvalidParameterException ("can't generate DSA parameters");

                        ipe.initCause (ipse);

                        throw ipe;

                }

        }

        else if (!getDefaults ())

        {

                throw new InvalidParameterException ("unsupported key size: " + modlen);

        }

}

public KeyPair generateKeyPair()

{

        if (random == null)

                {

                        random = new SecureRandom ();

                }

        BigInteger x = new BigInteger( 159, random );

        BigInteger y = g.modPow( x, p );

        return new KeyPair( new GnuDSAPublicKey(y,p,q,g), new GnuDSAPrivateKey(x,p,q,g));

        //return new KeyPair( public, private );

}

//These constants are Sun's Constants copied from the 

//Cryptography Specification

private boolean getDefaults()

{

        if( keysize == 512) {

                p = new BigInteger("fca682ce8e12caba26efccf7110e526db078b05edecbcd1eb4a208f3ae1617ae01f35b91a47e6df63413c5e12ed0899bcd132acd50d99151bdc43ee737592e17", 16);

                q = new BigInteger("962eddcc369cba8ebb260ee6b6a126d9346e38c5", 16);

                g = new BigInteger("678471b27a9cf44ee91a49c5147db1a9aaf244f05a434d6486931d2d14271b9e35030b71fd73da179069b32e2935630e1c2062354d0da20a6c416e50be794ca4", 16);

                return true;

        } else if( keysize == 768) {

                p = new BigInteger("e9e642599d355f37c97ffd3567120b8e25c9cd43e927b3a9670fbec5d890141922d2c3b3ad2480093799869d1e846aab49fab0ad26d2ce6a22219d470bce7d777d4a21fbe9c270b57f607002f3cef8393694cf45ee3688c11a8c56ab127a3daf", 16);

                q = new BigInteger("9cdbd84c9f1ac2f38d0f80f42ab952e7338bf511", 16);

                g = new BigInteger("30470ad5a005fb14ce2d9dcd87e38bc7d1b1c5facbaecbe95f190aa7a31d23c4dbbcbe06174544401a5b2c020965d8c2bd2171d3668445771f74ba084d2029d83c1c158547f3a9f1a2715be23d51ae4d3e5a1f6a7064f316933a346d3f529252", 16);

                return true;

        } else if( keysize == 1024) {

                p = new BigInteger("fd7f53811d75122952df4a9c2eece4e7f611b7523cef4400c31e3f80b6512669455d402251fb593d8d58fabfc5f5ba30f6cb9b556cd7813b801d346ff26660b76b9950a5a49f9fe8047b1022c24fbba9d7feb7c61bf83b57e7c6a8a6150f04fb83f6d3c51ec3023554135a169132f675f3ae2b61d72aeff22203199dd14801c7", 16);

                q = new BigInteger("9760508f15230bccb292b982a2eb840bf0581cf5", 16);

                g = new BigInteger("f7e1a085d69b3ddecbbcab5c36b857b97994afbbfa3aea82f9574c0b3d0782675159578ebad4594fe67107108180b449167123e84c281613b7cf09328cc8a6e13c167a8b547c8d28e0a3ae1e2bb3a675916ea37f0bfa213562f1fb627a01243bcca4f1bea8519089a883dfe15ae59f06928b665e807b552564014c3bfecf492a", 16);

                return true;

        }

        return false;

}

}