Mercurial > 510Connectbot
view src/com/five_ten_sg/connectbot/util/Encryptor.java @ 39:69bc44954bb5 tn5250
start tn5250 integration
author | Carl Byington <carl@five-ten-sg.com> |
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date | Tue, 10 Jun 2014 17:06:53 -0700 |
parents | 0ce5cc452d02 |
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/* * ConnectBot: simple, powerful, open-source SSH client for Android * Copyright 2007 Kenny Root, Jeffrey Sharkey * * Licensed 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. */ package com.five_ten_sg.connectbot.util; /** * This class is from: * * Encryptor.java * Copyright 2008 Zach Scrivena * zachscrivena@gmail.com * http://zs.freeshell.org/ */ import java.security.MessageDigest; import java.security.SecureRandom; import java.util.Arrays; import javax.crypto.Cipher; import javax.crypto.spec.IvParameterSpec; import javax.crypto.spec.SecretKeySpec; /** * Perform AES-128 encryption. */ public final class Encryptor { /** name of the character set to use for converting between characters and bytes */ private static final String CHARSET_NAME = "UTF-8"; /** random number generator algorithm */ private static final String RNG_ALGORITHM = "SHA1PRNG"; /** message digest algorithm (must be sufficiently long to provide the key and initialization vector) */ private static final String DIGEST_ALGORITHM = "SHA-256"; /** key algorithm (must be compatible with CIPHER_ALGORITHM) */ private static final String KEY_ALGORITHM = "AES"; /** cipher algorithm (must be compatible with KEY_ALGORITHM) */ private static final String CIPHER_ALGORITHM = "AES/CBC/PKCS5Padding"; /** * Private constructor that should never be called. */ private Encryptor() {} /** * Encrypt the specified cleartext using the given password. * With the correct salt, number of iterations, and password, the decrypt() method reverses * the effect of this method. * This method generates and uses a random salt, and the user-specified number of iterations * and password to create a 16-byte secret key and 16-byte initialization vector. * The secret key and initialization vector are then used in the AES-128 cipher to encrypt * the given cleartext. * * @param salt * salt that was used in the encryption (to be populated) * @param iterations * number of iterations to use in salting * @param password * password to be used for encryption * @param cleartext * cleartext to be encrypted * @return * ciphertext * @throws Exception * on any error encountered in encryption */ public static byte[] encrypt( final byte[] salt, final int iterations, final String password, final byte[] cleartext) throws Exception { /* generate salt randomly */ SecureRandom.getInstance(RNG_ALGORITHM).nextBytes(salt); /* compute key and initialization vector */ final MessageDigest shaDigest = MessageDigest.getInstance(DIGEST_ALGORITHM); byte[] pw = password.getBytes(CHARSET_NAME); for (int i = 0; i < iterations; i++) { /* add salt */ final byte[] salted = new byte[pw.length + salt.length]; System.arraycopy(pw, 0, salted, 0, pw.length); System.arraycopy(salt, 0, salted, pw.length, salt.length); Arrays.fill(pw, (byte) 0x00); /* compute SHA-256 digest */ shaDigest.reset(); pw = shaDigest.digest(salted); Arrays.fill(salted, (byte) 0x00); } /* extract the 16-byte key and initialization vector from the SHA-256 digest */ final byte[] key = new byte[16]; final byte[] iv = new byte[16]; System.arraycopy(pw, 0, key, 0, 16); System.arraycopy(pw, 16, iv, 0, 16); Arrays.fill(pw, (byte) 0x00); /* perform AES-128 encryption */ final Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM); cipher.init( Cipher.ENCRYPT_MODE, new SecretKeySpec(key, KEY_ALGORITHM), new IvParameterSpec(iv)); Arrays.fill(key, (byte) 0x00); Arrays.fill(iv, (byte) 0x00); return cipher.doFinal(cleartext); } /** * Decrypt the specified ciphertext using the given password. * With the correct salt, number of iterations, and password, this method reverses the effect * of the encrypt() method. * This method uses the user-specified salt, number of iterations, and password * to recreate the 16-byte secret key and 16-byte initialization vector. * The secret key and initialization vector are then used in the AES-128 cipher to decrypt * the given ciphertext. * * @param salt * salt to be used in decryption * @param iterations * number of iterations to use in salting * @param password * password to be used for decryption * @param ciphertext * ciphertext to be decrypted * @return * cleartext * @throws Exception * on any error encountered in decryption */ public static byte[] decrypt( final byte[] salt, final int iterations, final String password, final byte[] ciphertext) throws Exception { /* compute key and initialization vector */ final MessageDigest shaDigest = MessageDigest.getInstance(DIGEST_ALGORITHM); byte[] pw = password.getBytes(CHARSET_NAME); for (int i = 0; i < iterations; i++) { /* add salt */ final byte[] salted = new byte[pw.length + salt.length]; System.arraycopy(pw, 0, salted, 0, pw.length); System.arraycopy(salt, 0, salted, pw.length, salt.length); Arrays.fill(pw, (byte) 0x00); /* compute SHA-256 digest */ shaDigest.reset(); pw = shaDigest.digest(salted); Arrays.fill(salted, (byte) 0x00); } /* extract the 16-byte key and initialization vector from the SHA-256 digest */ final byte[] key = new byte[16]; final byte[] iv = new byte[16]; System.arraycopy(pw, 0, key, 0, 16); System.arraycopy(pw, 16, iv, 0, 16); Arrays.fill(pw, (byte) 0x00); /* perform AES-128 decryption */ final Cipher cipher = Cipher.getInstance(CIPHER_ALGORITHM); cipher.init( Cipher.DECRYPT_MODE, new SecretKeySpec(key, KEY_ALGORITHM), new IvParameterSpec(iv)); Arrays.fill(key, (byte) 0x00); Arrays.fill(iv, (byte) 0x00); return cipher.doFinal(ciphertext); } }