cordova-android/framework/src/com/phonegap/SimpleCrypto.java

/*
 * Code originally found on Android Snippets
 * Contributed to snippets Ferenc Hechler
 * Copyright (c) 2009 Ferenc Hechler
 */

package com.phonegap;

import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

public class SimpleCrypto {
	
	public static String encrypt(String seed, String cleartext) throws Exception {
		byte[] rawKey = getRawKey(seed.getBytes());
		byte[] result = encrypt(rawKey, cleartext.getBytes());
		return toHex(result);
	}
	
	public static String decrypt(String seed, String encrypted) throws Exception {
		byte [] rawKey = getRawKey(seed.getBytes());
		byte [] enc = toByte(encrypted);
		byte [] result = decrypt(rawKey, enc);
		return new String(result);
	}
	
	public static byte[] getRawKey(byte [] seed) throws Exception {
		KeyGenerator kgen = KeyGenerator.getInstance("AES");
		SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
		sr.setSeed(seed);
		kgen.init(128, sr);
		SecretKey skey = kgen.generateKey();
		byte[] raw = skey.getEncoded();
		return raw;
	}
	
	private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception {
		SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
		Cipher cipher = Cipher.getInstance("AES");
		cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
		byte[] encrypted = cipher.doFinal(clear);
		return encrypted;
	}
	
	private static byte[] decrypt(byte[] raw, byte[] encrypted) throws Exception {
		SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES");
		Cipher cipher = Cipher.getInstance("AES");
		cipher.init(Cipher.DECRYPT_MODE, skeySpec);
		byte[] decrypted = cipher.doFinal(encrypted);
		return decrypted;
	}
	
	public static String toHex(String txt)
	{
		return toHex(txt.getBytes());
	}
	
	public static String fromHex(String hex)
	{
		return new String(toByte(hex));
	}
	
	public static byte[] toByte(String hexString) {
		int len = hexString.length()/2;
		byte[] result = new byte[len];
		for (int i = 0; i < len; ++i)
		{
			result[i] = Integer.valueOf(hexString.substring(2*i, 2*i+2), 16).byteValue();
		}
		return result;
	}
	
	public static String toHex(byte[] buf) {
		if (buf == null)
		{
			return "";
		}
		StringBuffer result = new StringBuffer(2*buf.length);
		for (int i = 0; i < buf.length; i++)
		{
			appendHex(result, buf[i]);
		}
		return result.toString();
	}
	
	private final static String HEX = "01234567890ABCDEF";
	
	private static void appendHex(StringBuffer sb, byte b)
	{
		sb.append(HEX.charAt((b>>4)&0x0f)).append(HEX.charAt(b&0x0f));
	}
}