Is Coinjoin still safe?

[fanya]

A bit of background to the question: I accumulated Bitcoin many years ago and then moved away from Bitcoin due to my job, life and other circumstances.

I have lost my wallets but I am currently working on a solution and looking for access as I still have found something I forgot about in my house.

If I find access to my wallet, I want to use Coinjoin because I don't want the recipient of my transaction to know the original balance of my wallet.

Since I haven't been involved with Bitcoin for a long time, I have no idea about the current technical circumstances, but I came across an article reporting that Arkham Intelligence has developed algorithms and patterns to completely deanonymize transactions, even Coinjoins.

Can anyone tell me if this is true and what the current technical status is?

[Charles-Tim]

Since I haven't been involved with Bitcoin for a long time, I have no idea about the current technical circumstances, but I came across an article reporting that Arkham Intelligence has developed algorithms and patterns to completely deanonymize transactions, even Coinjoins.

And you believe that? That means you do not know how coinjoin is working. A transaction can be known to be from coinjoin, but the coin is mixed in a way that no tech can know which is which after the coinjoin.

[lontivero]

Hey Wasabi Wallet dev here.

... I want to use Coinjoin because I don't want the recipient of my transaction to know the original balance of my wallet.

You are right, this is the main use of a coinjoin: protect your financial privacy.

Since I haven't been involved with Bitcoin for a long time, I have no idea about the current technical circumstances,

There are basically two options currently: Wasabi Wallet and JoinMarket.

I came across an article reporting that Arkham Intelligence has developed algorithms and patterns to completely deanonymize transactions, even Coinjoins.

That's not so easy. Even one of the biggest and wealthier actors in this industry as ByBit offers chain analysts unbelievable bounties for those who help them to track the stolen funds across coinjoins and it seems they are not having any luck, see by yourself: https://www.lazarusbounty.com

Can anyone tell me if this is true and what the current technical status is?

Coinjoins help to protect you and your money from entities that want to track you, absolutely. Can it protects you from a wealthy and powerful organization like a big state intelligence department? I really don't know, it seems it can but I can't bet my hat. Can you --the user-- make a mistake after coinjoining that ruins all your wallet privacy? Yes, absolutely.

[takuma sato]

It's only reasonable to use privacy-friendly features to make transactions in Bitcoin. Just like how you don't want to show the contents of your bank account to the people you send money to with regular banking, you wouldn't want the same when using Bitcoin, and this is what coin tumblers/mixers/aggregators or whatever you want to call it attempt to solve. 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. So ideally you would want to end up with fresh coins, but I wonder how since the only guaranteed fresh coins are recently mined coins.

[FinneysTrueVision]

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.

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.

[ABCbits]

Since I haven't been involved with Bitcoin for a long time, I have no idea about the current technical circumstances, but I came across an article reporting that Arkham Intelligence has developed algorithms and patterns to completely deanonymize transactions, even Coinjoins.

I wouldn't trust what Arkham Intelligence say without proof. They have fair amount of controversy and their platform sometimes contain inaccurate/wrong data.

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. So ideally you would want to end up with fresh coins, but I wonder how since the only guaranteed fresh coins are recently mined coins.

FWIW, some blockchain analysis service and company who use it simply blacklist or label all CoinJoin UTXO as risky/dangerous. Certain type of CoinJoin TX are trivial detect, although linking between input & output is rather hard.

[takuma sato]

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.

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.

[lontivero]

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.

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.

[NotATether]

Since I haven't been involved with Bitcoin for a long time, I have no idea about the current technical circumstances, but I came across an article reporting that Arkham Intelligence has developed algorithms and patterns to completely deanonymize transactions, even Coinjoins.

Can anyone tell me if this is true and what the current technical status is?

It's rubbish.

If any of that was true then they would have been contracted by the FBI to deanonymize Whirlpool transactions from Samourai Wallet, and as far as I know, no deanonymization has been performed yet.

Simple, single-transaction coinjoins with a small UTXO set can be deenonymized, but not any types that are used in practice.

[nutildah]

If any of that was true then they would have been contracted by the FBI to deanonymize Whirlpool transactions from Samourai Wallet, and as far as I know, no deanonymization has been performed yet.

Simple, single-transaction coinjoins with a small UTXO set can be deenonymized, but not any types that are used in practice.

I'm pretty sure most of the deanonymization occurs only after coins have been moved from the coinjoin transaction output. For instance, the re-use of exchange (or other) addresses, and detection of patterns in send amounts, dates, and times. Yes, people really are that clumsy, even while matching patterns may not be 100% accurate in deanonymization. As was pointed out earlier, its moreso the fault of the user for not changing their behavior than the coinjoin process itself.

Can you --the user-- make a mistake after coinjoining that ruins all your wallet privacy? Yes, absolutely.

[KiaKia]

Why all this stress because you want to avoid exposing your wallet to the person you want to sent Bitcoin to? It's not a must to do this.

Instead you can do one of the following.

1. You can send the Bitcoin to a crypto exchange like Binance first, then withdraw from Binance to the person's Bitcoin address.

2. You can just move the Bitcoin around some wallet addresses and send to the person, if they try to track they will end up with empty wallets.

It will be hard for them to figure out which one belongs to you, I like the first idea though, they will noticed that it's been sent from Binance exchange. Unless you are not telling the truth about hiding transaction from a friend, maybe there is more than meet the eye.

[Frankolala]

Why all this stress because you want to avoid exposing your wallet to the person you want to sent Bitcoin to? It's not a must to do this.

Instead you can do one of the following.

1. You can send the Bitcoin to a crypto exchange like Binance first, then withdraw from Binance to the person's Bitcoin address.

2. You can just move the Bitcoin around some wallet addresses and send to the person, if they try to track they will end up with empty wallets.

It will be hard for them to figure out which one belongs to you, I like the first idea though, they will noticed that it's been sent from Binance exchange. Unless you are not telling the truth about hiding transaction from a friend, maybe there is more than meet the eye.

He can convert his bitcoin to monero in a decentralized exchange and move it around three or four different exchanges before converting it back to bitcoin and send it to the person that you want to send the coins. That will help hide your track if you cannot use Wassabi wallet or Joint Market.

[dkbit98]

If I find access to my wallet, I want to use Coinjoin because I don't want the recipient of my transaction to know the original balance of my wallet.

Than you should think about using Silent Payment addresses in future.
Cake wallet is one of the first wallet to support them, but there are others working on them like Blue wallet, Wasabi, Bitbox hardware wallet, etc.

Since I haven't been involved with Bitcoin for a long time, I have no idea about the current technical circumstances, but I came across an article reporting that Arkham Intelligence has developed algorithms and patterns to completely deanonymize transactions, even Coinjoins.

They obviously can't track everything, but user making mistakes with bad address management is making it easier.
Don't expect to have perfect privacy using Bitcoin, even with coinjoin or joinmarket, monero is much better for that purpose.
Another alternative is using confidential transactions with Liquid L-BTC, but that is separate federated chain.

[hd49728]

A bit of background to the question: I accumulated Bitcoin many years ago and then moved away from Bitcoin due to my job, life and other circumstances.

I have lost my wallets but I am currently working on a solution and looking for access as I still have found something I forgot about in my house.

If I find access to my wallet, I want to use Coinjoin because I don't want the recipient of my transaction to know the original balance of my wallet.

Coinjoin transactions are dangerous for users nowadays with more regulations against it from governments and centralized exchanges. If you don't have illegal issues with your past transactions from which you got those bitcoins, you can move it to other new wallets, and separate your initial bitcoins to different wallets and UTXOs, do it several rounds, before you can use your bitcoins with better privacy.

You can use Bitcoin full node and Tor for broadcasting your transactions.

Some tricks on doing this better.
https://bitcoiner.guide/privacy/
https://blockchair.com/bitcoin/privacy-o-meter

[betswift]

Since I haven't been involved with Bitcoin for a long time, I have no idea about the current technical circumstances, but I came across an article reporting that Arkham Intelligence has developed algorithms and patterns to completely deanonymize transactions, even Coinjoins.

I wouldn't trust what Arkham Intelligence say without proof. They have fair amount of controversy and their platform sometimes contain inaccurate/wrong data.

I agree, and we cannot be certain of anything a big entity does - no matter what it is, it's prone to mistakes, as it was said, there are cases where some transactions are going to be tagged anyway.