Java tutorial
/* * JBoss, Home of Professional Open Source. * Copyright 2012, Red Hat, Inc., and individual contributors * as indicated by the @author tags. See the copyright.txt file in the * distribution for a full listing of individual contributors. * * This is free software; you can redistribute it and/or modify it * under the terms of the GNU Lesser General Public License as * published by the Free Software Foundation; either version 2.1 of * the License, or (at your option) any later version. * * This software 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 * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this software; if not, write to the Free * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA * 02110-1301 USA, or see the FSF site: http://www.fsf.org. */ package org.picketlink.json.jose.crypto; import java.security.SecureRandom; import javax.crypto.SecretKey; import org.bouncycastle.crypto.BlockCipher; import org.bouncycastle.crypto.InvalidCipherTextException; import org.bouncycastle.crypto.modes.GCMBlockCipher; import org.bouncycastle.crypto.params.AEADParameters; import org.bouncycastle.crypto.params.KeyParameter; /** * AES/GSM/NoPadding encryption and decryption methods. * * <p> * See draft-ietf-jose-json-web-algorithms-26, section 5.1 and appendix 3. * * @author Giriraj Sharma */ public class AESGCM { /** * The standard Initialization Vector (IV) length (96 bits). */ public static final int IV_BIT_LENGTH = 96; /** * The standard authentication tag length (128 bits). */ public static final int AUTH_TAG_BIT_LENGTH = 128; /** * Generates a random 96 bit (12 byte) Initialization Vector(IV) for use in AES-GCM encryption. * * <p> * See draft-ietf-jose-json-web-algorithms-26, section 5.3. * * @param randomGen The secure random generator to use. Must be correctly initialized and not {@code null}. * * @return The random 96 bit IV, as 12 byte array. */ public static byte[] generateIV(final SecureRandom randomGen) { byte[] bytes = new byte[IV_BIT_LENGTH / 8]; randomGen.nextBytes(bytes); return bytes; } /** * Creates a new AES/GCM/NoPadding cipher. * * @param secretKey The AES key. Must not be {@code null}. * @param forEncryption If {@code true} creates an encryption cipher, else creates a decryption cipher. * @param iv The initialisation vector (IV). Must not be {@code null}. * @param authData The authenticated data. Must not be {@code null}. * * @return The AES/GCM/NoPadding cipher. */ private static GCMBlockCipher createAESGCMCipher(final SecretKey secretKey, final boolean forEncryption, final byte[] iv, final byte[] authData) { // Initialize AES cipher BlockCipher cipher = AES.createCipher(secretKey, forEncryption); // Create GCM cipher with AES GCMBlockCipher gcm = new GCMBlockCipher(cipher); AEADParameters aeadParams = new AEADParameters(new KeyParameter(secretKey.getEncoded()), AUTH_TAG_BIT_LENGTH, iv, authData); gcm.init(forEncryption, aeadParams); return gcm; } /** * Encrypts the specified plain text using AES/GCM/NoPadding. * * @param secretKey The AES key. Must not be {@code null}. * @param plainText The plain text. Must not be {@code null}. * @param iv The initialization vector (IV). Must not be {@code null}. * @param authData The authenticated data. Must not be {@code null}. * * @return The authenticated cipher text. * * @throws RuntimeException If encryption failed. */ public static AuthenticatedCipherText encrypt(final SecretKey secretKey, final byte[] iv, final byte[] plainText, final byte[] authData) { // Initialise AES/GCM cipher for encryption GCMBlockCipher cipher = createAESGCMCipher(secretKey, true, iv, authData); // Prepare output buffer int outputLength = cipher.getOutputSize(plainText.length); byte[] output = new byte[outputLength]; // Produce cipher text int outputOffset = cipher.processBytes(plainText, 0, plainText.length, output, 0); // Produce authentication tag try { outputOffset += cipher.doFinal(output, outputOffset); } catch (InvalidCipherTextException e) { throw new RuntimeException("Couldn't generate GCM authentication tag: " + e.getMessage(), e); } // Split output into cipher text and authentication tag int authTagLength = AUTH_TAG_BIT_LENGTH / 8; byte[] cipherText = new byte[outputOffset - authTagLength]; byte[] authTag = new byte[authTagLength]; System.arraycopy(output, 0, cipherText, 0, cipherText.length); System.arraycopy(output, outputOffset - authTagLength, authTag, 0, authTag.length); return new AuthenticatedCipherText(cipherText, authTag); } /** * Decrypts the specified cipher text using AES/GCM/NoPadding. * * @param secretKey The AES key. Must not be {@code null}. * @param iv The initialisation vector (IV). Must not be {@code null}. * @param cipherText The cipher text. Must not be {@code null}. * @param authData The authenticated data. Must not be {@code null}. * @param authTag The authentication tag. Must not be {@code null}. * * @return The decrypted plain text. * * @throws RuntimeException If decryption failed. */ public static byte[] decrypt(final SecretKey secretKey, final byte[] iv, final byte[] cipherText, final byte[] authData, final byte[] authTag) { // Initialise AES/GCM cipher for decryption GCMBlockCipher cipher = createAESGCMCipher(secretKey, false, iv, authData); // Join cipher text and authentication tag to produce cipher input byte[] input = new byte[cipherText.length + authTag.length]; System.arraycopy(cipherText, 0, input, 0, cipherText.length); System.arraycopy(authTag, 0, input, cipherText.length, authTag.length); int outputLength = cipher.getOutputSize(input.length); byte[] output = new byte[outputLength]; // Decrypt int outputOffset = cipher.processBytes(input, 0, input.length, output, 0); // Validate authentication tag try { outputOffset += cipher.doFinal(output, outputOffset); } catch (InvalidCipherTextException e) { throw new RuntimeException("Couldn't validate GCM authentication tag: " + e.getMessage(), e); } return output; } /** * Prevents public instantiation. */ private AESGCM() { } }