Yes, you can use a different service with the WabiSabi coinjoin protocol, even your own! With just one click, you can coordinate your own WabiSabi coinjoins yourself to create private coins, the code is entirely open source
With clearly inferior anonymity set, as every Wasabi user is practically using zkSNACKs' coordinator. You can't expect someone who merely wants to enhance their privacy, to run a coordinator, given there's a monster with millions in liquidity. He can't compete. WabiSabi coinjoins are nothing with no such liquidity.
Objectively, WabiSabi coinjoins are trustless. You do not have to trust the coordinator with your coins or your privacy.
I have to trust the coordinator for not attempting to perform a Sybil attack, and in the unnecessarily complicated case with zkSNACKs, I have to trust their chain analysis buddies with clear incentive to attack likewise, will neither attack.
In which case you detect the attack from the refusal of the private coin.
In which case I must have acquired one private coin without being Sybil attacked somehow.
You can coordinate your own WabiSabi coinjoins yourself to create private coins. The backend code is entirely open source.
I can't create private coins myself. I can create private coins only if I will mix mine with other people's coins.
The party identified as malicious by these refusals would still be the coordinator. Whether or not the coordinator is taking orders from another party about what coins to deny doesn't make a difference in regards to the attack being detected and defeated.
I know. That's why I took a hypothetical scenario where the coordinator isn't malicious. Even in that scenario, you have to be aware of the chain analysis company for not screwing the coinjoin up, with clear incentives that go against the coinjoin from happening uninterruptedly.
This would mean the Sybil attack gets detected and didn't even have a 100% chance of success in the first place.
How would it be detected, and by who? Surely not by the user, as they accept their coins can be disapproved and they gain no right to know why:
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