Quote from: Jean-Luc on September 21, 2015, 10:45:11 AM

But then you trust the initiator of the shuffle to not be an attacker himself. If he occupies the first k spots, it is as if the shuffle starts from k+1. At least in the Nxt core implementation, the shuffle creator is equal to all other participants, and will be penalized the same way if discovered to cheat.

I think in all variants the assumption is that there are non-attacker nodes participating. if the attacker is a passive statistics gathering attacker, i dont see how anything can be done to prevent (or even detect) such info gathering attackers

But if you control, the first two slots and assume at least one other non-attacking node, at least the initiator will get some privacy.

It would be interesting to see the math on how many shuffle rounds are needed to obtain practical privacy. I am thinking at least 10. Assuming there are 100 nodes ready to shuffle, then by making 10 random groupings of ~10 nodes to shuffle with, unless the attacker controls the majority of nodes, it seems to gain privacy.

James