Encryption support

[tommasobertoni]

As a communication library, it would be nice and, even more important, useful to have a way to enable encryption and secure the data transmission.

This idea is at it's very early stage, so I'll just write below a few use cases that I think they could become functionalities, once better defined (by me or by the community):

• server-level encryption: enables a common encryption on every node connected to an IrisServer
• multiple encryption protocols: to give more control and choice to the user
• channel-level encryption: with the ability to create channels to which nodes subscribe and publish messages, it would be nice to encrypt the single channel with a different certificate (or key?) from the others, to enable data obfuscation for the nodes that don't have the right configuration / permissions
• message-level encryption: if I want to publish a message to a public or crowded channel (e.g. broadcast) and still being able to transfer the information only to the nodes with the ability to decrypt it

At the moment, there isn't any infrastructure in place to support any kind of encryption, but if this idea gets some interest, it will be implemented and each of the above features will likely be moved in its own issue.