Topic: Can Coinjoin transactions be traced? Busting Bitcoin privacy myths! - page 4. (Read 1704 times)

There are probably more then a few people on this board sitting with 50+BTC from the early days who could setup a coordinator

Once again, if I setup a CoinJoin Coordinator for Wasabi users with a bit of tweaking it's not impossible. Getting people to use it would be the issue. But if I am charging no fees I can see where every TX came from and where they went.

Don't the users learn which inputs match up to which outputs?

In the simplest possible implementation where users meet up on IRC over tor or the like, yes they do. The next simplest implementation is where the users send their input and output information to some meeting point server, and the server creates the transaction and asks people to sign it. The server learns the mapping, but no one else does, and the server still can't steal the coins.

More complicated implementations are possible where even the server doesn't learn the mapping.

E.g. Using chaum blind signatures: The users connect and provide inputs (and change addresses) and a cryptographically-blinded version of the address they want their private coins to go to; the server signs the tokens and returns them. The users anonymously reconnect, unblind their output addresses, and return them to the server. The server can see that all the outputs were signed by it and so all the outputs had to come from valid participants. Later people reconnect and sign.

If a Fed was running a Whirlpool coordinator, they could perform a targeted attack where they only choose you to mix in rounds with 4 decoys so you gain a false sense of privacy.  Or, they could just rug pull you by not mixing your funds after you pay the coordinator fee.

- Can WabiSabi be traced?

Not unless you are the biggest whale in a coinjoin round with insufficient liquidity. Even outputs that do not have matching amounts cannot be traced to an owner on the input side - it’s even possible that the output changed hands as a payment to someone who did not own any funds on the input side at all:

Jambler is not a mixer. It buys coins from exchanges, miners etc. and sells them to real mixers.

Destroying the session deletes chip private key.

Can confirm, they stole a chip of mine a friend of mine that he hadn't yet spent. :/ Really fucking bad practice of ChipMixer to keep private keys, not gonna lie.
It was still there today morning and even when the news broke here; I he had not considered that private keys may have been backed up on CM servers to be honest.

I really can't believe this is an exit scam. The service seemed legitimate.

I'm really pissed off, and not because I lost money; fortunately, I had grasped that "don't leave coins to third parties" cliché. I'm so pissed off because I've been advertising and recommending this shit for months, in such a way that I'm practically part of this scam. And it's just feels awful.

It makes you question the integrity of the service you're currently carrying in your signature.

I clicked on the link in your signature, it says "Jambler.io mixing platform".  Did you know this is custodial?

I somewhat agree. People will just assume you shill Wasabi.

Look. I agree you believe you educate people about Bitcoin privacy, but we have repeated this conversation around solutions for privacy quite a lot of times. The fact that you still quote these whirlpool messages, as if they even mean something substantial, shows with what tenacity you're trying to sabotage Samourai.

There are no more mixer services here, stop trying to die on that hill. Or maybe you forgot to teleport your account to Altcoinstalks?

If there is a service coordinating payjoins between different wallets, which is ultimately what all of these methods boil down to, whose going to be interested in collecting the UTXO history of all the people who participate?

Same with CoinJoins and coordinators. Let's say the Fed was running a coordinator, and recorded every UTXO going inside it. Where's the privacy now?

Lol, you didn't fall for that did you?  The scammers who promote custodial "Mixer Sites" formed a mob to leave false accusations against anyone who tells the truth that Bitcoin is untraceable.

- Can payjoins be traced?

Not from the outside. However, the disadvantage of payjoins compared to other coinjoins is that the sender and receiver are completely aware of the coins owned by the other participant, which introduces a trusted single point of failure. In theory, a payjoin could be composed with inputs from more than two parties, however, this introduces a time element since some parties must pause their transaction and wait for others to join instead of paying instantaneously.

I'm educating people about Bitcoin privacy, just like I always have.

Anonymous money is quite literally the most important thing in the entire world, don't you agree?

Lol, you didn't fall for that did you?  The scammers who promote custodial "Mixer Sites" formed a mob to leave false accusations against anyone who tells the truth that Bitcoin is untraceable.

Everyone is going to die, why do you think that fact means we shouldn't have rationale debates?

Look man, I don't know what you're trying to do here. Don't you have enough with 15 neutral color tags but basically saying you're a piece of shit? Now you want to open a rational debate by quoting someone who is going to die? If it's because Wasabi pays you to represent them on the forum, the best thing you can do is stop doing it. Otherwise you're just going to inspire more hate.

- Can WabiSabi be traced?

Not unless you are the biggest whale in a coinjoin round with insufficient liquidity. Even outputs that do not have matching amounts cannot be traced to an owner on the input side - it’s even possible that the output changed hands as a payment to someone who did not own any funds on the input side at all:

--snip--

A malicious coordinator may tag users by providing them with different issuer parameters. When registering inputs a proof of ownership must be provided. If signatures are used, by covering the issuer parameters and a unique round identifier these proofs allow other participants to verify that everyone was given the same parameters.

A malicious coordinator could also delay the processing of requests in order to learn more through timing and ordering leaks. In the worst case, the coordinator can attempt to linearize all requests by delaying individual to recover the full set of labelled edges. This is possible when k = 1 and users have minimal dependencies between their requests and tolerate arbitrary timeouts but issue requests in a timely manner.

Similarly the coordinator may delay information such as the set of ownership proofs or the final unsigned transaction. In the case of the latter, this can be used to learn about links between inputs. This is because a signature can only be made after the details of the transaction are known. If the unsigned was only known to one user but multiple inputs have provided signatures, it follows that those inputs are owned by the same user.

Since the coordinator must be trusted with regards to denial of service a more practical variant of this attack would involve more subtle delays followed by sabotaging multiple successive rounds during the signing phase in order to learn of correlations between registrations while maintaining deniability.

Look man, I don't know what you're trying to do here.

Don't you have enough with 15 neutral color tags but basically saying you're a piece of shit?

Now you want to open a rational debate by quoting someone who is going to die?

If it's because Wasabi pays you to represent them on the forum, the best thing you can do is stop doing it. Otherwise you're just going to inspire more hate.

Okay then, I'll call your bluff again- Here's 20 non whale non matching outputs from WabiSabi coinjoins, try to identify the inputs owned by even a single one of the 20 outputs (which would be 5%):

01 bc1q032caguldmlrrztmrwhv5wqveyywdu2rtmd740
02 bc1q6vgwhsfkg343mmh27vc6prg3clsd4xu3p68vyd
03 bc1qre8jjpu8p9taw8j44r39z56vfr4sw64d4wyaj4
04 bc1qarharg76gfcrvskfw46f67vtqzd6hxa9pnspp5
05 bc1q4sexgt2p96x3ytnjjttp59w6mkj00kedal3xze
06 bc1qwrf50wpjws5mhdg2rhdu5hy7nqdtl8z94lp75n
07 bc1qz0tal2udfpr20x793fdw6v8lzp2qze7z5zje64
08 bc1qqw2h7fa3n8vyxgqru664fmft2trl9sqh9kz3fp
09 bc1qsud748whmum4gpt2qu52z8gqlgzcjyvhd5w2a5
10 bc1qctvxddyvxupjj8w82m8w5grzn59arstlrnaauw
11 bc1qq2fl05cmmhkr3pzg8elyr859v2fpcltynrk2j5
12 bc1qvwkrd3aecrvql5j8mqkmketvw6g6qwzt4juprq
13 bc1qhc2565fac4lrgyfq6n0mzc0l86jeptfnv2um9x
14 bc1qat6445gutyl3qdz3zhmdng9cdt92mevjlvaljs
15 bc1qk5f3mz0fetccey4nyyjedlrmqstkz2hmun96ha
16 bc1q4tpvm378a9d4n0xcnjtwfwujtr8eatjzvru8dx
17 bc1qd5epyjpj6vuejdppj24wew5n4n5rzepjx2xnay
18 bc1qgafud63me5mffn00g90ch08jjn5h20umzwxd62
19 bc1q5u3f2ldrtqa7ea79a8hcd8kssgw2gmalk4uej9
20 bc1qa6n7g7r4j3nv78gzgzmuvg56em4guppckqpz7r

Okay, here's all the payments that can be tracked from the two new participants of the Whirlpool coinjoin transaction:

Entrant 1: bc1q03c0443ausjjdxl2h6ud5m8c0dux0zyg3dqdj7 created 0.00170417 BTC in unmixed change sent to bc1q3fduld0l3r8nclyt5p3r7ak675tekurstn55tl.  Since this UTXO is not private, the sats were marked as unspendable and have not been recovered by the wallet owner  

Entrant 2: bc1qzc8zku26ej337huw5dlt390cy2r9kgnq7dhtys created 0.00191247 BTC in unmixed change sent to bc1qjlltxr443uy236wl4xhpxlr6dgsu0zltlv3m44. This UTXO was used in a second tx0 transaction, creating a huge trail of transactions that could be traced to each other  

The 2nd tx0 transaction created 0.00076348 BTC unmixed change which was sent to bc1qehd7gy8rza9mnzm9wnfjhgw82rp47wmqt7vpgy

Since this unmixed change is below the .001 pool minimum, it was consolidated in a 3rd tx0 with 3 other addresses owned by the same wallet:
31x8GPqrhzdaxiBJa9N5UisuoxbX1rAnHa
16Gw5WKjbxZmg1zhZQs19Sf61fbV2xGujx
3LZtsJfUjiV5EZkkG1fwGEpTe2QEa7CNeY

The 3rd tx0 transaction created .00200317 in unmixed change which was sent to bc1q2p7gdtyahct8rdjs2khwf0sffl64qe896ya2y5
This was spent in a 0.00190000 payment to 3B8cRYc3W5jHeS3pkepwDePUmePBoEwyp1 (a reused address)

That payment left .00008553 in change that was tracked to 3Dh7R7xoKMVfLCcAtVDyhJ66se82twyZSn and consolidated with two other inputs in a 4th tx0 transaction:
bc1qeuh6sds8exm54yscrupdk03jxphw8qwzdtxgde
3ByChGBFshzGUE5oip8YYVEZDaCP2bcBmZ

This 4th tx0 created .00533406 in unmixed change which was sent to bc1qzh699s75smwukg9jcanwnlkmkn38r79ataagd9 which was consolidated with 3 more addresses into a 5th tx0:
3F2qiWQJKQjF7XFjEo8FUYP3AU5AC6RqX8
3HAYYVKUpYbr2ARMdZJr9yVu8xi8UcxtPz
3GQtwwRK31wwCc22q6WS5sCgixUHsG5KaT

The 5th tx0 created 0.00058494 BTC in unmixed change that was sent to bc1qvh2zjcwwkj9y70xulla2semvlav3lty0p3l3w3
This was spent in a .00047290 payment to bc1qvzg8jq6wqtr5navn4e3ps4qrkk9r6n4h98gjck

That payment left .00008411 in change that was tracked to bc1qg6j0f0wfhpktt2l8uzdn48ct3um2xyur40eyzd and consolidated with another input into a 6th tx0 transaction:
31iZLXWfoywhuMZTPGxTkpzphzh2NXshpP

The 6th tx0 created .00753775 in unmixed change that was tracked to bc1qgfll2apc27yct6h2c8r8wq4kqhxjsfrudhhn5q
This was spent in a .00737000 payment to bc1q5emzer2t0sq5dez0zsrqgh6scvwn0n24xsladp (a reused address)

This payment left 0.00010896 BTC in change which has not been spent yet, but the payment only took place 11 days ago, so I assume it will eventually be spent, allowing the Whirlpool user to be tracked even further.

The flat pool entry fee structure is designed to incentivize worst privacy practices.  Since fees are not collected directly based on volume, it is cheaper to participate in a smaller pool and create more outputs than participate in a larger pool and create less outputs. Additionally, it incentivizes revealing common inputs ownership of premix UTXOs since it is cheaper to consolidate them to enter the pool once than to enter the pool with each UTXO individually.  Samourai has never explained why they purposely chose a fee structure that heavily penalizes the most private usage of their protocol.

Because of this backwards design, you can easily link premix inputs to postmix outputs in many cases.  Notice how this Whirlpool tx0 premix creates 70 outputs for 0.05 BTC - https://mempool.space/tx/63679c9ec82f246811acbab0c04cc0fc77ba050e1b6c23661d78afcfc13cf8aa

Notice how every single input of this Whirlpool exit transaction is a direct descendant of rounds created by the aforementioned premix transaction: https://mempool.space/tx/ce2f84f7c5ff74fb1da103acb7b279bd34f02f5e9e3a2e1b6417ce8b9b7392db

When many inputs used in the postmix exit transaction are created directly from a round that the premix transaction entered, it makes it trivial to trace the user through Whirlpool.  Fortunately, the user abandoned Whirlpool and upgraded to using the WabiSabi coinjoin protocol instead, which made him completely untraceable: https://mempool.space/address/bc1qjjw5gaglkycu2lm5fskl7qhktk0hec4a5me3da