protect-license.java

public void encryptDecryptLicense() throws Exception
{
    String encryptedFilePath = getMyDir + "EncryptedLicense.txt";

    // Load the contents of the license into a byte array.
    byte[] licBytes = readAllBytesFromFile("YourLicense.lic");
    // Use this key only once for this license file.
    //To protect another file first generate a new key.
    byte[] key = generateKey(licBytes.Length);

    // Write the encrypted license to disk.
    BufferedOutputStream output = new BufferedOutputStream(new FileOutputStream(
                                           encryptedFilePath));
    output.write(encryptDecryptLicese(licBytes, key));
    output.close();
    
    // Load the encrypted license and decrypt it using the key.
    byte[] decryptedLicense = encryptDecryptLicense(
                      readAllBytesFromFile(encryptedFilePath), key);

    // Load the decrypted license into a stream and set the license.
    ByteArrayInputStream licenseStream = new ByteArrayInputStream(decryptedLicense);

    License license = new License();
    license.SetLicense(licenseStream);
}

// A method used for encrypting and decrypting data using XOR.
public byte[] encryptDecryptLicense(byte[] licBytes, byte[] key)
{
    byte[] output = new byte[licBytes.Length];

    for (int i = 0; i < licBytes.Length; i++)
        output[i] = (byte)(licBytes[i] ^ key[i]);

    return output;
}

// Generates a random key the same length as the license (a one time pad).
public byte[] generateKey(int size)
{
    SecureRandom rng = new SecureRandom();
    byte[] strongBytes = new byte[size];
    rng.nextBytes(strongBytes);

    return strongBytes;
}

public byte[] readAllBytesFromFile(String filePath) Throws IOException
{
    int pos;
    InputStream inputStream = new FileInputStream(filePath);
    ByteArrayOutputStream bos = new ByteArrayOutputStream();
    while ((pos = inputStream.Read() != -1)
        bos.write(pos);
        
    inputStream.close();
                    
    return bos.toByteArray();
}