JoinMarket

JoinMarket is the software behind collaborative Bitcoin transactions on your MyNode. It creates CoinJoins — transactions that combine several participants' coins so an observer cannot match inputs to outputs — with the goal of improving the privacy and fungibility of bitcoin.

The hard part of a CoinJoin is not cryptography but coordination: the right coins have to be in the right place, in the right amount, at the right time. JoinMarket treats that as an economic problem and builds a market around it. Makers keep funds available and earn fees, takers pay those fees to have a join executed on demand, and competition pushes the fees down over time.

Critically, private keys never leave your machine. The protocol is structured so participants cannot steal from one another, which leaves essentially no counterparty risk. Fidelity bonds defend the market against sybil attacks, where an adversary floods it with fake makers in order to deanonymize joins.

The wallet is capable in its own right: native segwit addresses, five separate mixdepths for coin isolation, UTXO freezing for coin control, address labeling, fine-grained fee control, and protection against forced address reuse. PayJoin is supported for paying merchants privately, and a tumbler can run an automated sequence of joins unattended.

The Jam app in this marketplace is a graphical front end for the same software if the command line is not for you.