All messages are both signed and encrypted. I can't remember the order, but when it was determined some research was done about the various attacks to mitigate

All messages are both signed and encrypted. I can't remember the order, but when it was determined some research was done about the various attacks to mitigate the problem you allude to. I _believe_ we encrypt first, then sign, so that any tampering is detected before decryption begins. Using MEF is optional for the apps that use this library. But I don't see that it opens up new attack vectors. Feel free to enlighten me if you know more on this. And I agree with the other replies to your message about .NET being inherently insecure. It's trivially easy to inject code into any process, native or managed. If you have code executing on the machine (not some VM or runtime), from a security perspective you probably can own it if you like. So IMO the interesting attack vectors have to come in over the network.