The Joinmarket Community Wants to Improve Bitcoin’s Fungibility

February 23, 2017 - Bitcoin
The Joinmarket Community Wants to Improve Bitcoin’s Fungibility


Many people within the cryptocurrency environment are on a quest for fungible digital currency transactions. Some have opted to use altcoins while others patiently wait for Bitcoin implementations like Schnorr signatures and Tumblebit. For the time being, there is a platform that Bitcoiners can experiment with that uses coinjoin transactions called Joinmarket.


Coinjoin Transactions Using Joinmarket

Joinmarket was announced by Bitcoin developer Chris Belcher on in January 2015. The platform operates on either Linux or Windows and aims to improve the privacy of bitcoin transactions. Joinmarket utilizes what’s called coinjoin transactions, which means the protocol mixes multiple people’s transactions together to create obfuscation against transaction analysis.

The Joinmarket Community Wants to Improve Bitcoin's Fungibility
The concept of coinjoin transactions was first proposed by Bitcoin developer Gregory Maxwell.

“A coinjoin transaction requires other people to take part,” explains Belcher’s announcement. “The right resources (coins) have to be in the right place, at the right time, in the right quantity. This isn’t a software or tech problem, it is an economic problem. I propose a new kind of market is created that would allocate these resources in the best way.”

The protocol’s Github sources state that there are two groups within Joinmarket called market makers and market takers. By initiating a coinjoin transaction, takers pay a fee to the makers incentivizing both groups to perform the process.  “A form of smart contract is created, meaning the private keys will never be broadcasted outside of your computer, resulting in virtually zero risk of loss (aside from malware or bugs). As a result of free-market forces, the fees will eventually be next to nothing,” details Joinmarket.

The Joinmarket Community Wants to Improve Bitcoin's Fungibility
An example of a tested Joinmarket coinjoin transaction. Image courtesy of the Open Bitcoin Privacy Project.

Joinmarket’s Vulnerability This Past September

In September 2016, a vulnerability concern with Joinmarket was posted on Github. The announcement called “Joinmarket release 0.2.0 ameliorates this snooping attack” detailed that the platform’s privacy aspect was degraded.

“Joinmarket is a young project, there are some possible vulnerabilities which could be exploited to spy on every user,” explains Github issue #156. “It means that an attacker for free can learn what UTXOs belong to which maker, and can eliminate them when analyzing coinjoins on the blockchain. It’s not trivial to actually obtain all the UTXOs from a maker, but even learning a proportion of them is enough to spy on a large amount of coinjoins.”

This news caused concern towards using the project across many social cryptocurrency forums. However, crypto-privacy advocates still applauded the project and believed the platform was still in its infancy. Monero’s Riccardo Spagni had good things to say about Joinmarket when the vulnerability reached the public’s ears.

I’ll still continue to promote Joinmarket as the best coinjoin implementation, and the best combination of trustlessness + privacy + ease-of-use + liquidity for bitcoiners who don’t want to use altcoins or OTC trades or mining.

Joinmarket is still a popular coinjoin application within the community. The platform’s developers had also addressed the snooping attack in a matter of days with Joinmarket’s release version 0.2 and asked the entire community to update.

JoinMarket 0.2 released!  ameliorates the snooping attack! Protocol-breaking change so everyone must update

Photo published for JoinMarket-Org/joinmarket


joinmarket – CoinJoin implementation with incentive structure to convince people to take part

The community of Joinmarket users has a very active subreddit, and IRC channel for issues with the platform and general development discussion. The protocol’s code is updated regularly and has a vast array of guides for users to implement Joinmarket to the Bitcoin client or Electrum wallet support. At press time, Joinmarket has 80 orders by 62 counterparties on the platform’s order book.

“[The] aim is to improve the confidentiality and privacy of bitcoin transactions, as well as improve the capacity of the blockchain, therefore reduce costs,” explains the platform developers. “The concept has enormous potential, but had not seen much usage despite the multiple projects that implement it.”

Images courtesy of Shutterstock, Wiki commons, and the Open Bitcoin Privacy Project.