Create network protocol specification

[abailly-iohk]

Why

Hydra Head is first and foremost a protocol that's specified formally and is not particularly tied to a single language or paradigm, even though currently it's implemented in Haskell and the isomorphism property requires the use of the Cardano ledger which is available only in Haskell. Yet, it's not a far stretch to imagine people would be interested in building Head-compliant nodes in different technologies, either because they are more familiar with them, or to support different features not provided by the existing Haskell eco-system.

What

There already exist a public specification of the client API specified using AsyncAPI schema.

We want to publish a specification for the network protocol so that it should be possible to implement a hydra-node in any language supporting minimal networking capabilities.

How

The specification language is to be defined:

• The messages are expected to be serialised to a compact binary format and therefore the specification language used should support binary representations.
• Ouroboros-network uses CDDL to specify the structure of messages and state-machine diagrams to represent the protocol logic
• We could derive the exposed specification the existing Haskell types

[abailly-iohk]

Idea: Write a small "test" program in a non-Haskell language to interact with hydra-nodes, perhaps just as a "watchdog" style node that does not provide any interface and does not commit anything but participates in the off-chain signing process.