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+From: Matt Whitlock <bip@mattwhitlock.name>

+To: Gregory Maxwell <gmaxwell@gmail.com>

+Date: Fri, 04 Apr 2014 14:53:41 -0400

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+Cc: bitcoin-development <bitcoin-development@lists.sourceforge.net>

+Subject: Re: [Bitcoin-development] Presenting a BIP for Shamir's Secret

+ Sharing of Bitcoin private keys

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+

+On Friday, 4 April 2014, at 10:51 am, Gregory Maxwell wrote:

+> On Fri, Apr 4, 2014 at 10:16 AM, Matt Whitlock <bip@mattwhitlock.name> wrote:

+> > Honestly, that sounds a lot more complicated than what I have now. I made my current implementation because I just wanted something simple that would let me divide a private key into shares for purposes of dissemination to my next of kin et al.

+>

+> I suggest you go look at some of the other secret sharing

+> implementations that use GF(2^8), they end up just being a couple of

+> dozen lines of code. Pretty simple stuff, and they work efficiently

+> for all sizes of data, there are implementations in a multitude of

+> languages. There are a whole bunch of these.

+

+Okay, I will.

+

+> > Do you have a use case in mind that would benefit from byte-wise operations rather than big-integer operations? I mean, I guess if you were trying to implement this BIP on a PIC microcontroller, it might be nice to process the secret in smaller bites. (No pun intended.) But I get this feeling that you're only pushing me away from the present incarnation of my proposal because you think it's too similar (but not quite similar enough) to a threshold ECDSA key scheme.

+>

+> It lets you efficiently scale to any size data being encoded without

+> extra overhead or having additional primes. It can be compactly

+> implemented in Javascript (there are several implementations you can

+> find if you google), it shouldn't be burdensome to implement on a

+> device like a trezor (much less a real microcontroller).

+

+Those are fair points.

+

+> And yea, sure, it's distinct from the implementation you'd use for

+> threshold signing. A threshold singing one would lack the size agility

+> or the easy of implementation on limited devices. So I do think that

+> if there is to be two it would be good to gain the advantages that

+> can't be achieved in an threshold ECDSA compatible approach.

+

+I agree. I'll look into secret sharing in GF(2^8), but it may take me a few days.

+

+