"A form of smart contract is created" - where is this in the code?

[Impa10r]

I am a Bitcoin-related dev and I think I understand the tech pretty well. I am confused by the description of JAM in the readme. How exactly does it work? Are PSBTs sent around to all joiners for signing via IRC messages? Who is doing the coordination and posting the final transaction? Why to use the words "smart contract"?

Also, where is the "JoinMarket trading pit"? Is it centralized and prone to takedown? Does it use joinmarket.org domain name? I cannot open it, says "Sorry, you have been blocked" from any IP. What does this mean?

[PulpCattel]

See https://github.com/JoinMarket-Org/JoinMarket-Docs for the technical documentation. JoinMarket uses a maker-taker model, the taker is the one and only coordinator.

I don't know why smart contract was used, but if you read the README in this repo you see:

JoinMarket is software to create a special kind of bitcoin transaction called a CoinJoin transaction. Its aim is to improve the confidentiality and privacy of bitcoin transactions.

A CoinJoin transaction requires other people to take part. 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's an economic problem. JoinMarket works by creating a new kind of market that would allocate these resources in the best way.

One group of participants (called market makers) will always be available to take part in CoinJoins at any time. Other participants (called market takers) can create a CoinJoin at any time. The takers pay a fee which incentivizes the makers. 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.

We don't have a website that I know of (but there are plenty of scam ones), and certainly the trading pit is not there. Read the doc for the full details. At the moment, makers publish their offers, redundantly, on IRC servers and directory nodes (onion services run by community members mostly).

[kristapsk]

Basic protocol is here - https://github.com/JoinMarket-Org/JoinMarket-Docs/blob/master/Joinmarket-messaging-protocol.md

Also, where is the "JoinMarket trading pit"?

There is no such thing as single JoinMarket trading pit. You as a taker or obwatcher connect to various messaging channels, which you can configure, not only use defaults, and ask for offers and from that information you create your own local orderbook. It's somewhat similar how Bitcoin mempool works, where there is no single mempool, each node has it's own mempool that can and will differ from other nodes.

I would say most centralized single point of failure for JoinMarket currently is Tor network.

[Impa10r]

Yeah, thanks. I read all that and still don't have a clear picture on INTERNAL working. If there are bonds to post, it means the process is not trustless? How can these small bonds compensate all the joiners? There are also websites like https://jamapp.org/ and https://jamdocs.org/ - are they scams? ))

[kristapsk]

1. Bonds are not mandatory, bondless makers also have some small probability to participate in joins.

2. They don't compensate anything, they are technique against sibyl attacks. You lock in some bitcoins in timelocked address, that way it costs money to create lots of makers of different makers which would increase probability for spies to be all counterparties in your coinjoins, so you would not gain any privacy against them.

https://github.com/JoinMarket-Org/joinmarket-clientserver/blob/master/docs/fidelity-bonds.md

Jam sites are legit. It's separate project from JoinMarket itself, built on top of JoinMarket.