erpsuiteandroid/Apex Mobile/app/src/main/java/com/usai/util/Crypto.java

package com.usai.util;

import java.security.SecureRandom;

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

/**
 * Usage:
 * 
 * <pre>
 * String crypto = Crypto.encrypt(masterpassword, cleartext) 
 * ... 
 * String cleartext = Crypto.decrypt(masterpassword, crypto)
 * </pre>
 * 
 * @author ferenc.hechler
 */
public class Crypto
{
//    public static SecretKeySpec setSecretKey(String password) throws Exception {
//        SecretKeySpec key = null;
//        KeyGenerator kgen = KeyGenerator.getInstance(ALGORITHM);
//        SecureRandom sr = SecureRandom.getInstance("SHA1PRNG", "Crypto");
//        sr.setSeed(password.getBytes());
//        kgen.init(128, sr);
//        SecretKey secretKey = kgen.generateKey();
//        byte[] enCodeFormat = secretKey.getEncoded();
//        key = new SecretKeySpec(enCodeFormat, SecretKeySpec.ALGORITHM);
//
//        return key;
//    }

	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);
	}

	private static byte[] getRawKey(byte[] seed) throws Exception
	{
		
        KeyGenerator kgen = KeyGenerator.getInstance("AES");
        SecureRandom sr = SecureRandom.getInstance("SHA1PRNG", "Crypto");
        sr.setSeed(seed);
        kgen.init(128, sr);
        SecretKey secretKey = kgen.generateKey();	
        byte[] enCodeFormat = secretKey.getEncoded();
//        key = new SecretKeySpec(enCodeFormat, SecretKeySpec.ALGORITHM);
        return enCodeFormat;
//
//        return key;	
//		KeyGenerator kgen = KeyGenerator.getInstance("AES");
//		SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
//		sr.setSeed(seed);
//		kgen.init(128, sr); // 192 and 256 bits may not be available
//		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 = "0123456789ABCDEF";

	private static void appendHex(StringBuffer sb, byte b)
	{
		sb.append(HEX.charAt((b >> 4) & 0x0f)).append(HEX.charAt(b & 0x0f));
	}

}