protect-license-csharp.cs

public void EncryptDecryptLicense()
{
    string encryptedFilePath = MyDir + "EncryptedLicense.txt";

    // Load the contents of the license into a byte array.
    byte[] licBytes = File.ReadAllBytes("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.
    File.WriteAllBytes(encryptedFilePath, EncryptDecryptLicense(licBytes, key));

    // Load the encrypted license and decrypt it using the key.
    byte[] decryptedLicense;
    decryptedLicense = EncryptDecryptLicense(File.ReadAllBytes(encryptedFilePath), key);

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

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

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

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

    return output;
}

/// <summary>
/// Generates a random key the same length as the license (a one time pad).
/// </summary>
public byte[] GenerateKey(long size)
{
    RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider();
    byte[] strongBytes = new Byte[size];
    rng.GetBytes(strongBytes);

    return strongBytes;
}