Java tutorial
/* * Copyright (C) 2011 Vex Software LLC * This file is part of Votifier. * * Votifier 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 3 of the License, or * (at your option) any later version. * * Votifier 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 Votifier. If not, see <http://www.gnu.org/licenses/>. */ package com.vexsoftware.votifier.util.rsa; import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import java.net.URL; import java.security.KeyFactory; import java.security.KeyPair; import java.security.PrivateKey; import java.security.PublicKey; import java.security.spec.PKCS8EncodedKeySpec; import java.security.spec.X509EncodedKeySpec; import javax.xml.bind.DatatypeConverter; import net.minecraft.util.org.apache.commons.io.IOUtils; /** * Static utility methods for saving and loading RSA key pairs. */ public class RSAIO { /** * Saves the key pair to the disk. * * @param directory * The directory to save to * @param keyPair * The key pair to save * @throws Exception * If an error occurs */ public static void save(File directory, KeyPair keyPair) throws Exception { PrivateKey privateKey = keyPair.getPrivate(); PublicKey publicKey = keyPair.getPublic(); // Store the public key. X509EncodedKeySpec publicSpec = new X509EncodedKeySpec(publicKey.getEncoded()); FileOutputStream out = null; try { out = new FileOutputStream(directory + "/public.key"); out.write(DatatypeConverter.printBase64Binary(publicSpec.getEncoded()).getBytes()); } finally { try { out.close(); } catch (Exception exception) { // ignore } } // Store the private key. PKCS8EncodedKeySpec privateSpec = new PKCS8EncodedKeySpec(privateKey.getEncoded()); try { out = new FileOutputStream(directory + "/private.key"); out.write(DatatypeConverter.printBase64Binary(privateSpec.getEncoded()).getBytes()); } finally { try { out.close(); } catch (Exception exception) { // ignore } } } /** * Loads an RSA key pair from a directory. The directory must have the files * "public.key" and "private.key". * * @param directory * The directory to load from * @return The key pair * @throws Exception * If an error occurs */ public static KeyPair load(File directory) throws Exception { // Read the public key file. File publicKeyFile = new File(directory + "/public.key"); FileInputStream in = null; byte[] encodedPublicKey; try { in = new FileInputStream(directory + "/public.key"); encodedPublicKey = new byte[(int) publicKeyFile.length()]; in.read(encodedPublicKey); encodedPublicKey = DatatypeConverter.parseBase64Binary(new String(encodedPublicKey)); } finally { try { in.close(); } catch (Exception exception) { // ignore } } // Read the private key file. File privateKeyFile = new File(directory + "/private.key"); byte[] encodedPrivateKey; try { in = new FileInputStream(directory + "/private.key"); encodedPrivateKey = new byte[(int) privateKeyFile.length()]; in.read(encodedPrivateKey); encodedPrivateKey = DatatypeConverter.parseBase64Binary(new String(encodedPrivateKey)); } finally { try { in.close(); } catch (Exception exception) { // ignore } } // Instantiate and return the key pair. KeyFactory keyFactory = KeyFactory.getInstance("RSA"); X509EncodedKeySpec publicKeySpec = new X509EncodedKeySpec(encodedPublicKey); PublicKey publicKey = keyFactory.generatePublic(publicKeySpec); PKCS8EncodedKeySpec privateKeySpec = new PKCS8EncodedKeySpec(encodedPrivateKey); PrivateKey privateKey = keyFactory.generatePrivate(privateKeySpec); return new KeyPair(publicKey, privateKey); } /** * Loads an RSA public key from a URL. * * @param url * The URL that has the public key * @return * The public key * @throws Exception * If an error occurs */ public static PublicKey loadPublicKey(URL url) throws Exception { String publicKey = new String(IOUtils.toByteArray(url), "UTF-8") .replaceAll("(-+BEGIN PUBLIC KEY-+\\r?\\n|-+END PUBLIC KEY-+\\r?\\n?)", ""); KeyFactory keyFactory = KeyFactory.getInstance("RSA"); X509EncodedKeySpec publicKeySpec = new X509EncodedKeySpec(DatatypeConverter.parseBase64Binary(publicKey)); return keyFactory.generatePublic(publicKeySpec); } }