[bitcoin-dev] WabiSabi: a building block for coordinated CoinJoins

[Yuval Kogman <nothingmuch@woobling.org>]

Hi,

As part of research into how CoinJoins in general and Wasabi in
particular can be improved, we'd like to share a new building block
we're calling WabiSabi, which utilizes keyed verification anonymous
credentials instead of blind signatures to verify the honest
participation of users in centrally coordinated CoinJoin protocols.

Blind signatures have been used to facilitate centrally coordinated
CoinJoins, but require standard denominations, each associated with a
key, because blind signatures can only convey a single bit of
information from the signer to the verifier (both roles are the
coordinator in this setting). Anonymous credentials carry attributes,
and in our case these are homomorphic value commitments as in
Confidential Transactions.

Note that this is an early draft with a deliberately narrow scope, and
only introduces this abstract building block. At this stage we'd like
to solicit feedback and criticism about our scheme and inputs with
regards to its potential applications before proceeding. We do not not
(yet) address the structure of the CoinJoin transactions, fee
structures, or other implementation details, but discussion of these
aspects is welcome.

The repository is https://github.com/zkSNACKs/WabiSabi, and the latest
version is available here:
https://github.com/zkSNACKs/WabiSabi/releases/latest/download/WabiSabi.pdf