Crypto.java

package org.droidklavier.crypto;

import org.bouncycastle.crypto.BufferedBlockCipher;
import org.bouncycastle.crypto.PBEParametersGenerator;
import org.bouncycastle.crypto.engines.AESEngine;
import org.bouncycastle.crypto.generators.OpenSSLPBEParametersGenerator;
import org.bouncycastle.crypto.modes.CBCBlockCipher;
import org.bouncycastle.crypto.paddings.PaddedBufferedBlockCipher;
import org.bouncycastle.crypto.params.ParametersWithIV;
import org.bouncycastle.util.encoders.Base64;

import java.io.ByteArrayOutputStream;
import java.security.SecureRandom;
import java.util.Locale;

public class Crypto {

  public static String encrypt(String str, String password) {
    String enc_msg = getPlainText(str);
    String key = getKeyText(str);

    AESEngine blockCipher = new AESEngine();
    CBCBlockCipher cbcCipher = new CBCBlockCipher(blockCipher);
    BufferedBlockCipher cipher = new PaddedBufferedBlockCipher(cbcCipher);

    byte[] salt = new byte[8];
    SecureRandom secure = new SecureRandom();
    secure.nextBytes(salt);

    cipher.init(true, getKeyParamWithIv(password + key, salt, 128));

    byte[] encryptedData = new byte[cipher.getOutputSize(enc_msg.getBytes().length)];
    int noOfBytes = cipher.processBytes(enc_msg.getBytes(), 0, enc_msg.getBytes().length, encryptedData, 0);

    byte[] encryptedConfigData = null;

    try {
      cipher.doFinal(encryptedData, noOfBytes);

      ByteArrayOutputStream bos = new ByteArrayOutputStream();
      bos.write("Salted__".getBytes());
      bos.write(salt);
      bos.write(encryptedData);
      encryptedConfigData = bos.toByteArray();
      bos.close();
    } catch (Exception e) {
      e.printStackTrace();
    }

    if (encryptedConfigData != null) {
      encryptedData = Base64.encode(encryptedConfigData);
      return new String(encryptedData);
    }

    return "";
  }

  private static String getPlainText(String txt) {
    if ((txt.trim().equals("")) || (txt.length() < 50)) {
      return "";
    }
    String[] str_tbl = { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9",
      "a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l",
      "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x",
      "y", "z" };

    String strEnd = txt.substring(49, 50);

    int intStart = 0;
    for (int i = 0; i < str_tbl.length; i++) {
      if (!str_tbl[i].equals(strEnd.toLowerCase(Locale.getDefault()))) {
        continue;
      }
      intStart = i;
      break;
    }

    return txt.substring(intStart, intStart + 10);
  }

  private static String getKeyText(String txt) {
    if ((txt.trim().equals("")) || (txt.length() < 50)) {
      return "";
    }
    return txt.substring(30, 40);
  }

  private static ParametersWithIV getKeyParamWithIv(String keyphrase, byte[] salt, int aes_bit) {
    int iterationCount = 1;
    PBEParametersGenerator generator = new OpenSSLPBEParametersGenerator();
    generator.init(PBEParametersGenerator.PKCS5PasswordToBytes(keyphrase.toCharArray()), salt, iterationCount);
    return (ParametersWithIV) generator.generateDerivedParameters(aes_bit, 128);
  }
}