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SecureAgent.javaAPI DocExample3859Sat Jan 31 23:15:58 GMT 1998dcj.examples.security

SecureAgent

public class SecureAgent extends SimpleAgent
Source code from "Java Distributed Computing", by Jim Farley. Class: SecureAgent Example: 5-5 Description: An agent that includes the digital signature authentication of the AuthAgent, and adds the ability to encrypt messages using a symmetric cipher. NOTE: This class requires the JCE package, available only in the US and Canada.

(Omit source code)

Fields Summary
Identity
remoteAgent
Key
cryptKey
Constructors Summary
public SecureAgent(String host, int port)


      
        

    super(host, port);
    DataInputStream din = new DataInputStream(inStream);

    // Try to authenticate the remote agent
    try {
      String agentId = din.readUTF();
      int dataLen = din.readInt();
      byte[] data = new byte[dataLen];
      din.read(data);
      int sigLen = din.readInt();
      byte[] sig = new byte[sigLen];
      din.read(sig);

      if (!authenticate(agentId, data, sig)) {
        // Failed to authenticate, write error message, close socket and
        // return
        System.out.println("Failed to authenticate remote agent "
                           + agentId);
        closeConnection();
      }
      else {
        // Remote agent is authenticated, first message is a welcome
        addMsg("HELLO " + agentId);
      }
    }
    catch (Exception e) {
      closeConnection();
    }
Methods Summary
protected booleanauthenticate(java.lang.String id, byte[] data, byte[] sig)

    boolean success = false;
    PublicKey key = lookupKey(id);
    try {
      // Set up a signature with the agent's public key
      Signature agentSig = Signature.getInstance(key.getAlgorithm());
      agentSig.initVerify(key);
      // Try to verify the signature message from the agent
      agentSig.update(data);
      success = agentSig.verify(sig);

      if (success) {
        // Agent checks out, so initialize an identity for it
        remoteAgent = new Identity(id);
        remoteAgent.setPublicKey(key);
        // Get the agent's secret encryption key, too
        cryptKey = lookupSecretKey(id);
      }
    }
    catch (Exception e) {
      System.err.println("Failed to verify agent signature.");
      success = false;
    }

    return success;
public voidrun()

    // Go into infinite loop, sending messages, receiving responses and
    // processing them...

    DataInputStream din = (DataInputStream)inStream;
    DataOutputStream dout = (DataOutputStream)outStream;

    // Make an encryption Cipher for sending messages...
    String cryptAlgName = cryptKey.getAlgorithm();
    Cipher sendCipher = Cipher.getInstance(cryptAlgName);
    sendCipher.initEncrypt(cryptKey);
    // ...and a decryption Cipher for receiving them.
    Cipher receiveCipher = Cipher.getInstance(cryptAlgName);
    receiveCipher.initDecrypt(cryptKey);

    while (true) {
      String msg = nextMsg();
      if (msg != null) {
        String inMsg = "", inToken = "";
        try {
          // Send encrypted message to agent
          byte[] eData = sendCipher.crypt(msg.getBytes());
          dout.write(eData);

          // Read and decrypt message from agent
          int dataLen = din.readInt();
          eData = new byte[dataLen];
          din.read(eData);
          byte[] clearData = receiveCipher.crypt(eData);
          inMsg = new String(clearData);

          // Process the incoming message
          processMsg(inMsg);
        }
        catch (Exception e) {}
      }
    }