Serializable objects

[cvengler]

Hey,
I am curious on whether it would be possible to add a way on serializing and deserializing a HandshakeState, TransportState and StatelessTransportState.

I am unsure on whether that is "allowed" by Noise protocol specification, but I am currently studying protocols storing the responder side of an uncompleted handshake at the initiator through an AEAD construction, such as Rosenpass.

[kamo104]

@cvengler I implemented it in my fork:
snow

I don't think that noise specifies whether it's state can be saved. I haven't created a PR because this is still untested and I had to put it aside for a while. If you're still looking for a solution you may want to check it.