how do you defend against attackers who try to DOS by requesting to be part of a joined transaction but then fail to sign off on the transaction? This is the big problem with coinjoin that prevents it from scaling well. have you guys solved it somehow?
There is a penalty for leaving the connection before the darksend completes.
And how does that work?
You put up a collateral transaction that only the current master node can cash to get into the pool. If you misbehave in any way, the master node will cash it. Each time that costs 0.1DRK, so it could add up pretty quick if you're attacking it.
Masternode's are chosen randomly using a deterministic algorithm that can't be tampered with. This has a nice side effect, people will want to run full nodes to get the random fees. So we should have a pretty strong base of nodes.
Nodes could become quite profitable over time.