Can't the coordinator simply choose to put me in a round where there is only their and my coins joined?
There's no trust required since you would be able to detect this because the coordinator would have to block all other inputs from joining. We already discussed this, remember?
Could you explain how the Sybil attack will be detected?
Yes: You try to register a private coin in the same round as your non private coin that is the supposed target of the attack. If your private coin isn't denied, then the round is not under a Sybil attack.
I meant that your premixed coins are not going to be mixed in the same coinjoin. Each premixed coin will be mixed in separate coinjoins. They might share a coinjoin only if they are remixed.
However, I don't want to play it smart. I have not studied the whirlpool protocol, and that's all I interpret from simply reading a summary from their Telegram and Twitter accounts.
Okay, how about this scenario?
- Alice creates premix input A
- The first round creates postmix output B
- After waiting, B remixes creating C
- Alice creates premix input D
- Let's say the coordinator selects both C and D, (both owned by Alice) for the same coinjoin round. How should she respond?