The abstract problem is there is a set of objects and all peers have access to some subset of them. You want to communicated an ordered list of them plus some arbitrary data (your winning hash) to as many peers in as little data as possible.<p>It seems to me that the best solution is to have a well agreed upon function that keeps them in an ordered state and simply keep track of what transactions your neighbors know about, the information should largely already be there due to the fact that the transactions are dissiminated by a gossip protocol in the first place.