Wasabi coordinated a reported 100-participant Bitcoin CoinJoin

A Wasabi Wallet coordination round produced a Bitcoin CoinJoin transaction on June 6, 2019 that the project and contemporaneous reporting described as involving 100 participants. The transaction is preserved in Bitcoin’s public ledger under txid e4a789d16a24a6643dfee06e018ad27648b896daae6a3577ae0f4eddcc4d9174. That durable record establishes that the transaction occurred; the statement that 100 distinct people participated comes from Wasabi’s community and was reported by CoinDesk four days later, not from an identity field on the blockchain.

The milestone mattered because Bitcoin’s ledger is public by design. A conventional payment can expose relationships among inputs, outputs and later spending activity. CoinJoin addresses that problem by allowing several owners to cooperate on one transaction without surrendering control of their coins to a common custodian. The June 6 round was therefore less a market event than a live demonstration that privacy tooling could coordinate at a scale its developers had been pursuing.

What the transaction demonstrated

CoinJoin builds one Bitcoin transaction from inputs supplied by multiple participants. Each participant signs the combined transaction only after checking that the intended output is present. The transaction cannot become valid unless the required input signatures are supplied, so coordination does not require one operator to take custody of every participant’s bitcoin.

The privacy benefit comes from ambiguity. Where a round creates several outputs of the same amount, an outside observer cannot identify the input-to-output mapping merely by reading the ledger. A larger pool can enlarge that ambiguity for qualifying equal-value outputs. It does not make Bitcoin activity invisible, and it does not guarantee that every output receives an anonymity set equal to the number of claimed participants.

That distinction is important for the June 6 record. The blockchain proves the transaction’s inputs, outputs, inclusion and amounts, but it does not prove that every input belonged to a different human. One person can control multiple inputs, and later spending behavior can recombine coins or reveal links. Network observation, wallet mistakes, address reuse and interaction with identity-collecting services can also weaken privacy beyond what the transaction graph alone suggests.

From proposal to usable coordination

Gregory Maxwell had outlined the core cooperative-transaction idea in a January 28, 2013 Bitcoin forum post. His point was both practical and analytical: the common assumption that all inputs in a transaction share one owner is not always valid when different people jointly construct and sign it.

By 2019, Wasabi Wallet had packaged a centrally coordinated form of CoinJoin into consumer software and routed coordination over Tor. Contemporary accounts show the community repeatedly approaching the project’s 100-participant target with rounds reported at 94, 97, 92 and 99 participants before the June 6 transaction. Those figures document the coordination effort, but they remain participant counts attributed to the project rather than identities independently recoverable from the chain.

The achievement also exposed the tradeoff. More participants can improve ambiguity and share transaction overhead, yet assembling a large group requires users to be online, register inputs, provide outputs and sign within the round’s timing rules. Failed or delayed signatures can force another round. Privacy gains therefore depended on software reliability and participant behavior as much as on Bitcoin’s consensus rules.

What was knowable on June 6

The defensible conclusion on June 6, 2019 was narrow: Wasabi had completed a verifiable CoinJoin transaction that its community described as the first round to reach 100 participants. It was evidence that collaborative Bitcoin privacy could work at meaningful scale, not proof of perfect anonymity, universal fungibility or immunity from blockchain analysis. No price reaction can be responsibly assigned to the transaction from the surviving sources, and this reconstruction makes no such claim.