Creating an activation key generator in JAVA

Question

I want to create a key generator for my telephone applications. I am currently using an external service to do this work, but I'm a little worried that the service might shut down one day, so I will be a little pickle.

How authentication works.

• The public key stored on the phone.
• When the user requests a key, the “Phone Identifier” is sent to the “key generation service”, and the encrypted key key is returned and stored inside the license file.
• On the phone, I can check if there is a key for the current phone using the getPhoneId () method, which I can check with the current phone and provide or not grant access to the functions.

I like it and it works well, however I want to create my own “key generation service” on my own website.

Requirements:

• Public and private key
• Encryption: (Bouncy Castle)
• Written in JAVA
• Must support getApplicationId () (so that many applications can use the same key generator) and getPhoneId () (to get the phone ID from an encrypted license file)
• I want to be able to send ApplicationId and PhoneId to a service to generate a license key.

Can someone give me some guidance on how to do this? I tried using java encryption but definitely not an expert and can not find anything that will help me.

I will need to use the list of Java classes that I need to instantiate.

Answer 1

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Java, ( Signature Sign and Verify):

import java.security.*;

public class Main {
  public static void main(String args[]) throws Exception {
    Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());

    // our server, imagine it a webservice
    KeyServer server = new KeyServer(42);

    // init client with a copy of public key from server
    KeyClient client = new KeyClient(server.getPublicKey());

    // create string that identifies phone and application
    byte[] data = (getPhoneId() + ":" + getApplicationId()).getBytes("utf-8");

    // send data to server for signature creation
    byte[] digitalSignature = server.signData(data);

    // verify on client side
    System.out.println("verified = " + client.verifySig(data, digitalSignature));

    // bad data
    byte[] wrongData = ("anotherPhoneId" + ":" + getApplicationId()).getBytes("utf-8");
    System.out.println("verified = " + client.verifySig(wrongData, digitalSignature));

    // bad signature
    digitalSignature[5] = (byte) 0xff;
    System.out.println("verified = " + client.verifySig(data, digitalSignature));
  }

  private static String getPhoneId() {
    return "somephone";
  }

  private static String getApplicationId() {
    return "someapp";
  }

  public static class KeyClient {

    private PublicKey _publicKey;
    private Signature _signer;

    public KeyClient(PublicKey publicKey) {
      if (publicKey == null) {
        throw new NullPointerException("publicKey");
      }
      _publicKey = publicKey;

      try {
        _signer = Signature.getInstance("SHA1withRSA");
      } catch (NoSuchAlgorithmException e) {
        throw new RuntimeException("failed to get Signature", e);
      }
    }

    public boolean verifySig(byte[] data, byte[] sig) throws Exception {
      synchronized (_signer) {
        _signer.initVerify(_publicKey);
        _signer.update(data);
        return (_signer.verify(sig));
      }
    }
  }

  public static class KeyServer {

    private KeyPair _keyPair;
    private Signature _signer;

    public KeyServer(int seed) {
      try {
        _keyPair = generateKeyPair(seed);
      } catch (Exception e) {
        throw new RuntimeException("failed to generate key pair for seed " + seed, e);
      }

      try {
        _signer = Signature.getInstance("SHA1withRSA");
      } catch (NoSuchAlgorithmException e) {
        throw new RuntimeException("failed to get Signature", e);
      }
    }

    public PublicKey getPublicKey() {
      return _keyPair.getPublic();
    }

    public byte[] signData(byte[] data) throws InvalidKeyException, SignatureException {
      synchronized (_signer) {
        _signer.initSign(_keyPair.getPrivate());
        _signer.update(data);
        return (_signer.sign());
      }
    }

    private KeyPair generateKeyPair(long seed) throws Exception {
      KeyPairGenerator keyGenerator = KeyPairGenerator.getInstance("RSA");
      SecureRandom rng = SecureRandom.getInstance("SHA1PRNG", "SUN");
      rng.setSeed(seed);
      keyGenerator.initialize(2048, rng);
      return (keyGenerator.generateKeyPair());
    }

  }
}

Answer 2

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