encrypt and decrypt property file value in java

Question

I am looking for a way to encrypt a password in a configuration file that is being read by a Java program. Currently, I read-in the password from the text file, but that lea

Answer 1

Here are some helpers to encrypt or decrypt using AES in Java:

public static final String AES = "AES";

/**
 * Encrypt a value and generate a keyfile.
 * If the keyfile is not found, then a new one will be created.
 * 
 * @throws GeneralSecurityException
 * @throws IOException if an I/O error occurs
 */
public static String encrypt(String value, File keyFile)
        throws GeneralSecurityException, IOException {
    if (!keyFile.exists()) {
        KeyGenerator keyGen = KeyGenerator.getInstance(CryptoUtils.AES);
        keyGen.init(128);
        SecretKey sk = keyGen.generateKey();
        FileWriter fw = new FileWriter(keyFile);
        fw.write(byteArrayToHexString(sk.getEncoded()));
        fw.flush();
        fw.close();
    }

    SecretKeySpec sks = getSecretKeySpec(keyFile);
    Cipher cipher = Cipher.getInstance(CryptoUtils.AES);
    cipher.init(Cipher.ENCRYPT_MODE, sks, cipher.getParameters());
    byte[] encrypted = cipher.doFinal(value.getBytes());
    return byteArrayToHexString(encrypted);
}

/**
 * Decrypt a value.
 * 
 * @throws GeneralSecurityException
 * @throws IOException if an I/O error occurs
 */
public static String decrypt(String message, File keyFile)
        throws GeneralSecurityException, IOException {
    SecretKeySpec sks = getSecretKeySpec(keyFile);
    Cipher cipher = Cipher.getInstance(CryptoUtils.AES);
    cipher.init(Cipher.DECRYPT_MODE, sks);
    byte[] decrypted = cipher.doFinal(hexStringToByteArray(message));
    return new String(decrypted);
}

private static SecretKeySpec getSecretKeySpec(File keyFile)
        throws NoSuchAlgorithmException, IOException {
    byte[] key = readKeyFile(keyFile);
    SecretKeySpec sks = new SecretKeySpec(key, CryptoUtils.AES);
    return sks;
}

private static byte[] readKeyFile(File keyFile)
        throws FileNotFoundException {
    Scanner scanner = new Scanner(keyFile).useDelimiter("\\Z");
    String keyValue = scanner.next();
    scanner.close();
    return hexStringToByteArray(keyValue);
}

private static String byteArrayToHexString(byte[] b) {
    StringBuffer sb = new StringBuffer(b.length * 2);
    for (int i = 0; i < b.length; i++) {
        int v = b[i] & 0xff;
        if (v < 16) {
            sb.append('0');
        }
        sb.append(Integer.toHexString(v));
    }
    return sb.toString().toUpperCase();
}

private static byte[] hexStringToByteArray(String s) {
    byte[] b = new byte[s.length() / 2];
    for (int i = 0; i < b.length; i++) {
        int index = i * 2;
        int v = Integer.parseInt(s.substring(index, index + 2), 16);
        b[i] = (byte) v;
    }
    return b;
}

Just call the appropiate method.