Quote from: takuma sato on Today at 09:36:05 PM

Quote from: FinneysTrueVision on May 07, 2025, 10:10:26 PM

As far as I know, Arkham is not capable of deanonymizing coinjoins. They are an explorer that can tag an address based on certain patterns, like an address that gets swept into Binance’s cold wallet can be assumed to be a Binance deposit address. They automatically tag many addresses as coinjoin addresses, but there is a flaw in their algorithm that sometimes mislabels addresses from batch payments as coinjoin addresses. Even if they can identify an address as having participated in a coinjoin, they can’t tell you anything beyond that unless a participant does something to compromise their privacy, like coinjoining to a reused address.

Quote from: takuma sato on May 07, 2025, 09:27:03 PM

My question is, when it comes to blacklisted coins, doesn't CoinJoin have the same problem as regular online mixers? Since you never know where the coins come from, you may end up blacklisted coins and when you go and make a transaction, you may own blacklisted coins that show up at the end of some service that uses whatever filters they use to detect so called blacklisted coins.

In a coinjoin, you know exactly where your coins come from. They come from your own wallet. The privacy comes from making a transaction with many participants, so outside observers don’t know the precise origin of your coins. You don’t really end up with coins that belonged to a blacklisted user, but your coins can end up on a blacklist as a consequence of seeking to improve your privacy via coinjoin.

How can you own coins end up in a blacklist if coinjoin works as you mention? I thought coinjoin was a transaction that had a lot of different people aggregating into the same transaction in enough smaller amounts that it would be impossible to tell what amounts belong to previous addresses. But the way you put it is that you create your own receiving addresses and then just somehow resend it to yourself? I need to research coinjoin since I thought it was working more similar to mixers.

A coinjoin is just a bitcoin transactions as any other bitcoin transaction, the only thing that makes them different is that it is created by many people instead of only one. That means that those people can do whatever they want with their money, they can send it to someone else or send it to themselves. Here you can see that someone decided to donate to El Salvador bitcoin address in a Wasabi coinjoin: https://mempool.space/tx/8c58beccc25acc763c528515b3a23bb92eeb6dc41b519ef681f76dfcc76cc19d#vout=433 Was that the only one making a payment? There is no way to know, however we can assume that most people send the money back to themselves because that's how Wasabi works by default.

Now, it is so obvious that that transaction is a Wasabi coinjoin that someone could decide to reject coins coming from it and in fact that's what many exchanges do: they just rejects those coins.

But the real problem with of this is not technical at all, people who wants privacy and deal with exchanges are not different from those who want a hot icecream. If you use an exchange then do not coijoin and if you coinjoin do not use an exchange because exchanges are the perhaps the main reason why we don't have privacy in bitcoin and coinjoins are one of the fee tools that allow us to have some privacy in bitcoin.