The state of Bitcoin multisig

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 (<a href="https:&#x2F;&#x2F;copay.io" rel="nofollow">https:&#x2F;&#x2F;copay.io</a>) does but there is no standard way to do this.<p>There are other issues. For example, Coinbase doesn&#x27;t support it fully. See this thread for more info: <a href="https:&#x2F;&#x2F;twitter.com&#x2F;coinfabrik&#x2F;status&#x2F;661992065841123328" rel="nofollow">https:&#x2F;&#x2F;twitter.com&#x2F;coinfabrik&#x2F;status&#x2F;661992065841123328</a> but other wallet services like Coinkite does: <a href="http:&#x2F;&#x2F;blog.coinfabrik.com&#x2F;independently-generating-your-private-key-for-coinkite&#x2F;" rel="nofollow">http:&#x2F;&#x2F;blog.coinfabrik.com&#x2F;independently-generating-your-pri...</a>

Two cents from an apps developer: few months ago I&#x27;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 Bitcoin documentation is a mess, BitcoinJ documentation is also outdated, so finally I investigated BitcoinJ source code pretty deeply to go forward.