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/* * Copyright (c) 1997, 2007, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation.  Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code 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 * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package com.sun.crypto.provider; import java.math.BigInteger;import java.security.*;import java.security.spec.*;import javax.crypto.spec.DHParameterSpec;import javax.crypto.spec.DHGenParameterSpec; /* * This class generates parameters for the Diffie-Hellman algorithm. * The parameters are a prime, a base, and optionally the length in bits of * the private value. * * <p>The Diffie-Hellman parameter generation accepts the size in bits of the * prime modulus and the size in bits of the random exponent as input. * The size of the prime modulus defaults to 1024 bits. * * @author Jan Luehe * * * @see java.security.AlgorithmParameters * @see java.security.spec.AlgorithmParameterSpec * @see DHParameters */public final class DHParameterGeneratorextends AlgorithmParameterGeneratorSpi {     // The size in bits of the prime modulus    private int primeSize = 1024;     // The size in bits of the random exponent (private value)    private int exponentSize = 0;     // The source of randomness    private SecureRandom random = null;     /**     * Initializes this parameter generator for a certain keysize     * and source of randomness.     * The keysize is specified as the size in bits of the prime modulus.     *     * @param keysize the keysize (size of prime modulus) in bits     * @param random the source of randomness     */    protected void engineInit(int keysize, SecureRandom random) {        if ((keysize < 512) || (keysize > 1024) || (keysize % 64 != 0)) {            throw new InvalidParameterException("Keysize must be multiple "                                                + "of 64, and can only range "                                                + "from 512 to 1024 "                                                + "(inclusive)");        }        this.primeSize = keysize;        this.random = random;    }     /**     * Initializes this parameter generator with a set of parameter     * generation values, which specify the size of the prime modulus and     * the size of the random exponent, both in bits.     *     * @param params the set of parameter generation values     * @param random the source of randomness     *     * @exception InvalidAlgorithmParameterException if the given parameter     * generation values are inappropriate for this parameter generator     */    protected void engineInit(AlgorithmParameterSpec genParamSpec,                              SecureRandom random)        throws InvalidAlgorithmParameterException {            if (!(genParamSpec instanceof DHGenParameterSpec)) {                throw new InvalidAlgorithmParameterException                    ("Inappropriate parameter type");            }             DHGenParameterSpec dhParamSpec = (DHGenParameterSpec)genParamSpec;             primeSize = dhParamSpec.getPrimeSize();            if ((primeSize<512) || (primeSize>1024) || (primeSize%64 != 0)) {                throw new InvalidAlgorithmParameterException                    ("Modulus size must be multiple of 64, and can only range "                     + "from 512 to 1024 (inclusive)");            }             exponentSize = dhParamSpec.getExponentSize();            if (exponentSize <= 0) {                throw new InvalidAlgorithmParameterException                    ("Exponent size must be greater than zero");            }             // Require exponentSize < primeSize            if (exponentSize >= primeSize) {                throw new InvalidAlgorithmParameterException                    ("Exponent size must be less than modulus size");            }    }     /**     * Generates the parameters.     *     * @return the new AlgorithmParameters object     */    protected AlgorithmParameters engineGenerateParameters() {        AlgorithmParameters algParams = null;         if (this.exponentSize == 0) {            this.exponentSize = this.primeSize - 1;        }         if (this.random == null)            this.random = SunJCE.RANDOM;         try {            AlgorithmParameterGenerator paramGen;            DSAParameterSpec dsaParamSpec;             paramGen = AlgorithmParameterGenerator.getInstance("DSA");            paramGen.init(this.primeSize, random);            algParams = paramGen.generateParameters();            dsaParamSpec = (DSAParameterSpec)                algParams.getParameterSpec(DSAParameterSpec.class);             DHParameterSpec dhParamSpec;            if (this.exponentSize > 0) {                dhParamSpec = new DHParameterSpec(dsaParamSpec.getP(),                                                  dsaParamSpec.getG(),                                                  this.exponentSize);            } else {                dhParamSpec = new DHParameterSpec(dsaParamSpec.getP(),                                                  dsaParamSpec.getG());            }            algParams = AlgorithmParameters.getInstance("DH", "SunJCE");            algParams.init(dhParamSpec);        } catch (InvalidParameterSpecException e) {            // this should never happen            throw new RuntimeException(e.getMessage());        } catch (NoSuchAlgorithmException e) {            // this should never happen, because we provide it            throw new RuntimeException(e.getMessage());        } catch (NoSuchProviderException e) {            // this should never happen, because we provide it            throw new RuntimeException(e.getMessage());        }         return algParams;    }}