I've read a lot about protocols for mental poker without a trusted server, but I'm interested in the possibility of a faster, more practical protocol that relaxes that criterion a bit and "trusts" a third-party server whose trustworthiness can be easily verified (or whose cheating can be easily proven).
For example, let's say a game server is set up that sends messages to players, and every message it sends is signed with its public key and has details about the request that generated it, a timestamp, and so on. So if the server ever, for example, forged a timestamp, someone could publish a signed message from the server, subsequently signed by another timestamp service, proving this. Likewise, if the server ever cheated on someone's behalf, an insider could easily publish a set of signed messages proving that he received information from the server to which he was not entitled.
The hard part, I imagine, would be out-of-band communication. That is, guy at a server on the phone with a player. But that too could be easily exposed by a whistleblower by publishing the information he got out-of-band in a way that makes it statistically unlikely that he could have guessed it (for example, his info signed by another timestamp server earlier than his legal reveal).
Is there such a protocol known/in use? Am I missing something obvious about why this would be impractical and/or not significantly faster than the untrusted server protocols?