
The state of Bitcoin multisig - alcio
https://medium.com/@alcio/the-state-of-bitcoin-multisig-82b3bf09b1ca#.i5p6z085t
======
wslh
There is an important part of the multisig puzzle missing in the article: the
need for an out of band protocol to communicate copayers for joining a wallet
and spending bitcoins. This is something that Copay
([https://copay.io](https://copay.io)) does but there is no standard way to do
this.

There are other issues. For example, Coinbase doesn't support it fully. See
this thread for more info:
[https://twitter.com/coinfabrik/status/661992065841123328](https://twitter.com/coinfabrik/status/661992065841123328)
but other wallet services like Coinkite does:
[http://blog.coinfabrik.com/independently-generating-your-
pri...](http://blog.coinfabrik.com/independently-generating-your-private-key-
for-coinkite/)

~~~
kang
I haven't read how the wallets are implementing multisig but what is this out-
of-band protocol you are talking about?

If I want to spend coins from a multisig address, I create a transaction, sign
it with my key and send it to the other party who can sign it and relay it or
send it back to me and I can relay it. It's a very simple protocol.

~~~
wslh
The way you send it to another party is not standarized. Think in your
grandpa, he would want to just create a transaction while everything else
happens behind the scene. Sending an email is a manual process and you need to
recheck if the other party received it.

Beyond this, there is a bigger reason: if you want a risk service like Sig3 or
CryptoCorp you should adapt the system to every multisig wallet while if you
have an standarized way to communicate you wrote an standard system.

~~~
kang
You can send an email(messaging) behind the scene, need not be manual nor is a
task that require standardization.

Sig3 is more secure theoretically but its an overkill & non-requirement
nevertheless. Why not have Sig4? Sig100 would be theoretically even more
secure!

~~~
wslh
> You can send an email(messaging) behind the scene

So... how Coinbase handles it, what is the format? Coinkite? Copay? The nth
popular wallet? You can easily see that you need a standarization, it doesn't
matter if its by email, morse, or slack.

Now, Sig3 is the name of a service, with Sig3 you can use any n-m wallet.

------
kushti
Two cents from an apps developer: few months ago I've implemented multisig on
top of BitcoinJ(generic signing code providing a signature dependless on
current state of a partially signed transaction). The experience was truly
horrible. Bitcoin documentation is a mess, BitcoinJ documentation is also
outdated, so finally I investigated BitcoinJ source code pretty deeply to go
forward.

~~~
statoshi
BitcoinJ is no frills and unfortunately doesn't have much development manpower
despite its popularity. I'm actually in the midst of trying to debug an edge
case issue I'm hitting within BitcoinJ itself.

