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415 sats \ 4 replies \ @oomahq 5 May \ parent \ on: Coinjoin Workshop aka Emessbee 🐝: Unstoppable Coinjoins with No Coordinator bitcoin
I think the problem of sybil participants is not that they stall the process, but that they enter the anonset with lots of UTXOs, manage to include several of their UTXOs in each coinjoin, and then trivially trace the other participants who coinjoin with several of their UTXOs.
oh, I didn't realize that
oops
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On the other hand it's not clear to me how (or even if?) Whirlpool and Wasabi were able to mitigate this threat.
Fidelity bonds arbitrarily raise the cost to be a sybil attacker (e.g. you need to cough up and provably freeze for some time 4X more BTC than you want to coinjoin, for instance).
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Whirlpool was extremely easy to Sybil attack since the attack victims pay the mining fees to move the coins of attackers.
Wasabi's coinjoins require users to pay for their own block space, which aligns incentives to defend against attackers passively spying on rounds for free.
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Emessbee also requires users to pay for their own block space. The mining fee is calculated after all change addresses are submitted, then divided up equally among all participants, and deducted from the amount that would otherwise go to users as change
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