title: WCF and protobuf with message signification
body: <p>I have an abstract base class can be serialized using protobuf:</p>
  
  <pre><code>[ProtoContract]
  class DataPacket
  {
    [ProtoMember(1)]
    public byte[] Data {set;get;}
    [ProtoMember(2)]
    public byte[] Sign {set;get;}
    [ProtoMember(3)]
    public long UserId {set;get;}
    [ProtoMember(4)]
    public DateTime Stamp {set;get;}
  }
  </code></pre>
  
  <p>The challenge is to make WCF to signify every sended and check signature of every received message. There two static methods in one static class:</p>
  
  <pre><code>bool Verify(DataPacket pack) 
  </code></pre>
  
  <p>and </p>
  
  <pre><code>void Sign(DataPacket pack)
  </code></pre>
  
  <p>So if verification method returns false we need to throw an <code>Exception</code> else - default WCF behavior.
  Is it possible to solve?</p>