Android Open Source - Munin-for-Android Encryption Helper

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License

The source code is released under:

GNU General Public License

Java Source Code

package com.chteuchteu.munin.hlpr;
/*from  w  ww.  j  av  a2s .  c  o m*/
import java.security.SecureRandom;

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

public class EncryptionHelper {
  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); // 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;
  }

  private 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;
  }

  private 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));
  }
}

Java Source Code List

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