Crypto.java

package io.evercam.androidapp.utils;

//import static Constants.EnEncryptionKey;

import java.security.SecureRandom;

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

public class Crypto
{
    public static final String EncryptionKey = "sajjadpp";
    private final static int JELLY_BEAN_4_2 = 17;

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

    public static String decrypt(String encrypted) throws Exception
    {
        byte[] rawKey = getRawKey(EncryptionKey.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 = null;
        if(android.os.Build.VERSION.SDK_INT >= JELLY_BEAN_4_2)
        {
            sr = SecureRandom.getInstance("SHA1PRNG", "Crypto");
        }
        else
        {
            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));
    }

}