From: Matt Whitlock <bip@mattwhitlock.name>
To: Dev Random <c1.devrandom@niftybox.net>
Date: Sat, 29 Mar 2014 13:38:10 -0400
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Cc: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] Presenting a BIP for Shamir's Secret
	Sharing of Bitcoin private keys
Precedence: list

On Saturday, 29 March 2014, at 10:25 am, Dev Random wrote:
> On Sat, 2014-03-29 at 11:44 -0400, Matt Whitlock wrote:
> > On Saturday, 29 March 2014, at 11:08 am, Watson Ladd wrote:
> > > https://freedom-to-tinker.com/blog/stevenag/new-research-better-wallet-security-for-bitcoin/
> > 
> > Thanks. This is great, although it makes some critical references to an
> > ACM paper for which no URL is provided, and thus I cannot implement it.
> > 
> > A distributed ECDSA notwithstanding, we still need a way to decompose a
> > BIP32 master seed into shares. I am envisioning a scenario in which I
> 
> It would seem that threshold ECDSA with keys derived from separate seeds
> has better security properties than one seed that is then split up.  The
> main thing is that there is no single point of attack in the generation
> or signing.

No contest here. But can threshold ECDSA work with BIP32? In other words, can a threshold ECDSA public key be generated from separate, precomputed private keys, or can it only be generated interactively? Maybe the BIP32 master seeds have to be generated interactively, and then all sets of corresponding derived keys are valid signing groups?

Threshold ECDSA certainly sounds nice, but is anyone working on a BIP for it? I would take it on myself, but I don't understand it well enough yet, and publicly available information on it seems lacking. I proposed this Shamir Secret Sharing BIP as an easily understood, easily implemented measure that we can use today, with no changes to existing Bitcoin software. It's low-hanging fruit.