| /* |
| * $HeadURL: http://juliusdavies.ca/svn/not-yet-commons-ssl/trunk/src/java/org/apache/commons/ssl/Certificates.java $ |
| * $Revision: 121 $ |
| * $Date: 2007-11-13 21:26:57 -0800 (Tue, 13 Nov 2007) $ |
| * |
| * ==================================================================== |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, |
| * software distributed under the License is distributed on an |
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| * KIND, either express or implied. See the License for the |
| * specific language governing permissions and limitations |
| * under the License. |
| * ==================================================================== |
| * |
| * This software consists of voluntary contributions made by many |
| * individuals on behalf of the Apache Software Foundation. For more |
| * information on the Apache Software Foundation, please see |
| * <http://www.apache.org/>. |
| * |
| */ |
| package org.apache.kerby.util; |
| |
| import java.math.BigInteger; |
| import java.security.GeneralSecurityException; |
| import java.security.KeyException; |
| import java.security.KeyFactory; |
| import java.security.PrivateKey; |
| import java.security.PublicKey; |
| import java.security.interfaces.DSAParams; |
| import java.security.interfaces.DSAPrivateKey; |
| import java.security.interfaces.RSAPrivateCrtKey; |
| import java.security.spec.DSAPublicKeySpec; |
| import java.security.spec.RSAPublicKeySpec; |
| |
| /** |
| * Utility class for deriving a public key from a given private key. |
| */ |
| public class PublicKeyDeriver { |
| |
| /** |
| * Utility method for deriving a public key from a given private key. |
| * |
| * @param key private key for which we need a public key (DSA or RSA). |
| * @return the corresponding public key |
| * @throws java.security.GeneralSecurityException if it didn't work |
| */ |
| public static PublicKey derivePublicKey(PrivateKey key) throws GeneralSecurityException { |
| if (key instanceof DSAPrivateKey) { |
| DSAPrivateKey dsaKey = (DSAPrivateKey) key; |
| DSAParams keyParams = dsaKey.getParams(); |
| BigInteger g = keyParams.getG(); |
| BigInteger p = keyParams.getP(); |
| BigInteger q = keyParams.getQ(); |
| BigInteger x = dsaKey.getX(); |
| BigInteger y = q.modPow(x, p); |
| DSAPublicKeySpec keySpec = new DSAPublicKeySpec(y, p, q, g); |
| return KeyFactory.getInstance("DSA").generatePublic(keySpec); |
| } else if (key instanceof RSAPrivateCrtKey) { |
| RSAPrivateCrtKey rsaKey = (RSAPrivateCrtKey) key; |
| BigInteger modulus = rsaKey.getModulus(); |
| BigInteger exponent = rsaKey.getPublicExponent(); |
| RSAPublicKeySpec keySpec = new RSAPublicKeySpec(modulus, exponent); |
| return KeyFactory.getInstance("RSA").generatePublic(keySpec); |
| } else { |
| throw new KeyException("Private key was not a DSA or RSA key"); |
| } |
| } |
| } |
| |