Coinjoiner: a WabiSabi coordinator that aims to improve privacy

[Coinjoiner21]

Coinjoiner - making Bitcoin privacy great again
Website: https://coinjoiner.com/
Coordinator URI: https://api.coinjoiner.com/

What is Coinjoiner? Coinjoiner is a WabiSabi coordinator which aims to improve privacy in Bitcoin.

The problem: Privacy has always been a major problem in Bitcoin.  Since the inception of bitcoin, there have been many ideas around the protection of privacy, from centralized mixers to coinjoin techniques.  But, very few survived to this day.  The reason is that governments have been extremely hostile, not only with mixers that are subjected to "money laundering", but even to developers who write the code.  This has lead to an environment where people are scared to work on Bitcoin privacy, and which, as result, directs those who want privacy to privacy-oriented altcoins such as Monero.  

The only privacy solutions to Bitcoin right now are WabiSabi coinjoins and Joinmarket.  We believe that WabiSabi is theoretically superior solution to Joinmarket in most regards.  The only client which supports WabiSabi is Wasabi Wallet (or forks of it).

We understand that Wasabi has gained a bad reputation throughout the years, due to a series of bad decisions made by the founders (zkSNACKs), such as the hiring of blockchain analysis and the blacklisting of inputs based on that analysis[1], or vulnerabilities found in the client that could have undermined users' privacy[2].  However, Wasabi Wallet is open-source, it's been working normally even after the takedown of the main coordinator of zkSNACKs.  Various coordinators have spawned since then (see liquisabi.com).

We believe there is room for improving Wasabi by focusing on:

- resistance to potential partitioning attacks by the coordinator (using blinding key, round ID etc.)
- the improvement of minor but important UI caveats.  For example, more flexible transaction construction (such as paying to many addresses), or discovering coordinators via nostr without having to manually search for them on the internet.
- the development of an alternative light client that is not vulnerable to supply-chain attacks such as those possible in the current Wasabi Wallet implementation in C#.

Coinjoiner is a WabiSabi coordinator which will use leftover coins from coinjoins to fund the development of these improvements.  It's a cost-efficient way for privacy seekers to get their coins private while knowing they directly contribute to the improvement of the space.

We want to be completely open and transparent regarding our mission.  Coinjoiner charges no direct coordination fee. It only gets leftover dust. From Wasabi Wallet documentation[3]:

In rare cases the output decomposition contains change (maximum of 10 000 sats per coinjoin), this leftover goes to the coordinator. This is because creating such small amounts would harm privacy and ends up being more expensive than just forfeiting it.

Furthermore, we also think there's room for education on WabiSabi coinjoins, like how they work or why they are superior to other on-chain privacy solutions.  

Because we are a new coordinator, we don't have much liquidity, so you would do us great service if you could point your Wasabi Wallet client to our coordinator.  


We believe Bitcoin deserves more resilient and robust privacy solutions.  We are here to answer any questions.

[1] https://bitcointalk.org/index.php?topic=5405325.0
[2] https://github.com/GingerPrivacy/GingerWallet/discussions/116
[3] https://docs.wasabiwallet.io/using-wasabi/CoinJoin.html#more-details

[BattleDog]

Nice to see someone actually doing something about the one-coordinator to rule them all problem instead of just tweeting about it.

More WabiSabi coordinators is objectively good for users, as long as the trust assumptions are clear. Wasabi's UX is decent and the protocol is solid on paper, but having zkSNACKs as the de-facto single choke point has always felt like training wheels for chain-analysis companies. If your coordinator is genuinely censorship-free, doesn't log more than it strictly needs, and is transparent about how that leftover dust is handled, you'll already be an upgrade in a lot of people's threat models.

[Coinjoiner21]

More WabiSabi coordinators is objectively good for users, as long as the trust assumptions are clear.

Yes, we are working on clarifying all the trust assumptions.  In theory, WabiSabi is completely trustless*, but in practice, the coordinator software developed by Wasabi can attack the user in various ways. 

* completely trustless in the sense that de-anonymizing users through sybil attack (n-1 inputs belonging to the attacker) becomes very expensive over the course of time.

If your coordinator is genuinely censorship-free, doesn't log more than it strictly needs, and is transparent about how that leftover dust is handled, you'll already be an upgrade in a lot of people's threat models.

We hope so.  We don't censor anything.  We only keep the standard Logs.txt, but we're working on configuring the coordinator software to print as little as possible in the log file.  As for the funding, we will talk more about how the development process will begin once we have enough liquidity.