Quote from: Mike Hearn on March 12, 2014, 04:29:36 PM

I was under the impression that n-of-m ecdsa was outlined some time ago by this paper:

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.67.9913&rep=rep1&type=pdf

Perhaps I have missed something? Your technique does however appear a lot simpler for the 2-of-2 case specifically, which is often useful for various contract protocols.

Wow, thanks for the paper. I will definitely check it out.

My goal is to implement this idea:

1. People crowdfund a bunch of money for some company.
2. Unlike usual schemes, company cannot use all that money how they want, but only in some pre-determined portions. E.g. when they start crowdfunding, they need a guarantee of $1M, but they will spend first $100K on a prototype, then $300K for initial batch, then if everything is well, for the rest. Crowdfunding contract will take care of putting all money in such buckets so they are not spendable right away.
3. If founders begin spending money not in a way investors like, investors can unlock the funds and get them back to everyone with a majority vote.

TLDR: "If you start fucking with us, we will automatically get most of the cash back".

Alternatively, every chunk of money could be allowed or denied via a majority vote, but that may be too cumbersome. It's probably more efficient to simply allow spending some smaller portions and rescue the rest in case of a problem.

Alternatively (2), crowdfunding process itself can be broken down in independent stages, but that is also cumbersome for the same reason. It's simpler just to crowdfund the total $1M only once, begin the work and then take it back if needed.