Security Considerations

This is an open discussion of security considerations between a Crestron processor and Crescendo Cloud.

Communication

All servers, production and development, accept IPSec connections. A demonstration of IPSec will be available for download ~~in a few weeks (posted 2016-03-16)~~ whenever our standalone virtual machine router is finished. Our IPSec tunnels have been live for months (posted 2016-09-02).

Authentication

Authentication is the process of a processor proving that it is the processor it purports to be. Presently, Crescendo Cloud uses open registration and authentication of any processor (or service spoofing a processor) based on model, serial number, and MAC address.

Password Authentication

There is no sense having a password and its consequent inconveniences (loss, change, retrieval) only to transmit the password in plaintext. Therefore, a zero-knowledge password proof should be used.

SRP

The obvious solution is to use Secure Remote Password protocol, which would allow processors to manage passwords themselves. However, implementing public-key encryption in SIMPL+ will be onerous, ~~perhaps impossible~~ (definitely not impossible with arbitrary-precision arithmetic).

SRP would provide an optional secure channel using the session key. Processor-side encryption is probably not a good idea, especially since SIMPL+ does not use compiler optimization.

Nonce

If Crescendo Cloud manages passwords instead of processors, a less technically challenging solution is to use a cryptographic nonce. Writing a cryptographic hash function in SIMPL+ will be easier than implementing SRP. MD5 is used for Digest Access Authentication~~, but Mawka might be the best password hash function for this purpose since most of the computation could be delegated to the server~~.

adelyte / crescendo-cloud-driver