EncodeDecodeAES.java

package org.oobd.crypt.AES;

import java.security.SecureRandom;
import java.security.Security;

import java.lang.reflect.*;

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

import org.oobd.base.Base64Coder;

public class EncodeDecodeAES {

	private final static String HEX = "0123456789ABCDEF";
	private final static int JELLY_BEAN_4_2_MB1 = 17;
	private final static byte[] key = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
			0, 0, 0 };

	static {
		Security.addProvider(new org.spongycastle.jce.provider.BouncyCastleProvider());
	}

	public static String encrypt(String seed, String cleartext)
			throws Exception {
		byte[] rawKey = getRawKey(seed.getBytes());
		byte[] result = encrypt(rawKey, cleartext.getBytes());
		String fromHex = toHex(result);
		String base64 = new String(Base64Coder.encodeString(fromHex));
		return base64;
	}

	public static String decrypt(String seed, String encrypted)
			throws Exception {
		byte[] seedByte = seed.getBytes();
		System.arraycopy(seedByte, 0, key, 0,
				((seedByte.length < 16) ? seedByte.length : 16));
		String base64 = new String(Base64Coder.decodeString(encrypted));
		byte[] rawKey = getRawKey(seedByte);
		byte[] enc = toByte(base64);
		byte[] result = decrypt(rawKey, enc);
		return new String(result);
	}

	public static byte[] encryptBytes(String seed, byte[] cleartext)
			throws Exception {
		byte[] rawKey = getRawKey(seed.getBytes());
		byte[] result = encrypt(rawKey, cleartext);
		return result;
	}

	public static byte[] decryptBytes(String seed, byte[] encrypted)
			throws Exception {
		byte[] rawKey = getRawKey(seed.getBytes());
		byte[] result = decrypt(rawKey, encrypted);
		return result;
	}

	private static byte[] getRawKey(byte[] seed) throws Exception {
		KeyGenerator kgen = KeyGenerator.getInstance("AES"); // , "SC");
		// KeyGenerator kgen = KeyGenerator.getInstance("AES" , "SC");
		SecureRandom sr = null;
                Class<?> act =null;
                 try{
                      act = Class.forName("android.os.Build$VERSION");
                 }
                 catch(Exception e){
                     
                 }
		if (act != null && compareVersionStrings(act.getField("RELEASE").get(null).toString(), "4.2") > -1) {
			sr = SecureRandom.getInstance("SHA1PRNG", "Crypto");
		} else {
			sr = SecureRandom.getInstance("SHA1PRNG");
		}
		sr.setSeed(seed);
		try {
			kgen.init(256, sr);
			// kgen.init(128, sr);
		} catch (Exception e) {
			// Log.w(LOG,
			// "This device doesn't suppor 256bits, trying 192bits.");
			try {
				kgen.init(192, sr);
			} catch (Exception e1) {
				// Log.w(LOG,
				// "This device doesn't suppor 192bits, trying 128bits.");
				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");

                 // das war die Variante, wie sie unter Android lief
                Cipher cipher = Cipher.getInstance("AES"); // /ECB/PKCS7Padding", "SC");
		// Cipher cipher = Cipher.getInstance("AES/ECB/PKCS7Padding", "SC");

                // und dies ist der Versuch unter Java Swing...
//                Cipher cipher = Cipher.getInstance("AES/ECB/PKCS7Padding", "SC");
                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");

                 //das war die Variante, wie sie unter Android lief
		Cipher cipher = Cipher.getInstance("AES"); // /ECB/PKCS7Padding", "SC");
		// Cipher cipher = Cipher.getInstance("AES/ECB/PKCS7Padding", "SC");

                // und dies ist der Versuch unter Java Swing...
//Cipher          cipher = Cipher.getInstance("AES/ECB/PKCS7Padding", "SC");
                cipher.init(Cipher.DECRYPT_MODE, skeySpec);
		byte[] decrypted = cipher.doFinal(encrypted);
		return decrypted;
	}

	// taken from http://stackoverflow.com/a/6702029/1927807
	public static int compareVersionStrings(String str1, String str2) {
		String[] vals1 = str1.split("\\.");
		String[] vals2 = str2.split("\\.");
		int i = 0;
		while (i < vals1.length && i < vals2.length
				&& vals1[i].equals(vals2[i])) {
			i++;
		}

		if (i < vals1.length && i < vals2.length) {
			int diff = Integer.valueOf(vals1[i]).compareTo(
					Integer.valueOf(vals2[i]));
			return diff < 0 ? -1 : diff == 0 ? 0 : 1;
		}

		return vals1.length < vals2.length ? -1
				: vals1.length == vals2.length ? 0 : 1;
	}

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

}