Hello guys,

In the past few weeks, I spent a few hours researching a way to sign a message with a multi-sig wallet. After a lot of tests, I discovered the Bitcoin #322 Proposal.


    
As a Bitcoin association, whose goal is to educate people about Bitcoin in our city, we enable everyone to become a member of our association for a few thousands sats per year. To do so, we use Swiss Bitcoin Pay.
It's an app' which enables us (and shops to) to export easily our accounting if needed. We also onboard merchants with this app', 'cause it's UX friendly, very easy to use too; and the accounting part is very usefull in lots of countries.


The problem is that we use a multi-sig wallet, as some other associations and companies.
However, as I previously said, it's currently impossible to sign a message with a multi-sig wallet, 'cause BIP 322 hadn't been pushed for a few months / years.

It also means that we can't prove that we own an address by signing a message with our multi-sig wallet; which is an information asked in some regulated countries (in Switzerland for example). It's not a KYC thing, just a "proof of addresses ownership".


Not being able to sign a message with a multi-sig wallet is also a lack in our Bitcoin ecosystem, and I hope it gonna change in the next few weeks / months.

    

Atm, I only spent a couple of hours learning about how Bitcoin signatures work.
My only discovery is that the ECDSA function is neither linear, nor commutative. If it was, the solution would have been very easy to implement.
Got a couple ideas, but I need to go further in my researches and understanding of ECDSA.


To sum up: if this thread (and BIP) was forgottent, please make it live again. We need that in our ecosystem.