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From: Mike Hearn <mike@plan99.net>
To: Jeff Garzik <jgarzik@bitpay.com>
Cc: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] Presenting a BIP for Shamir's Secret Sharing of Bitcoin private keys
Date: Sat, 29 Mar 2014 14:36:07 +0100	[thread overview]
Message-ID: <CANEZrP0WAMGV_ki3+9eFPaLQQVS7BJQ1c1c7KDuQatTeun-VwA@mail.gmail.com> (raw)
In-Reply-To: <CAJHLa0N0YCHfBeDq+QLqK3ZVWD-rAx85MXvX4OBqSoQqgCXm2w@mail.gmail.com>

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Right - the explanation in the BIP about the board of  directors is IMO a
little misleading. The problem is with splitting a private key is that at
some point, *someone* has to get the full private key back and they can
then just remember the private key to undo the system. CHECKMULTISIG avoids
this.

I can imagine that there may be occasional uses for splitting a wallet seed
like this, like for higher security cold wallets, but I suspect an ongoing
shared account like a corporate account is still best off using
CHECKMULTISIG or the n-of-m ECDSA threshold scheme proposed by Ali et al.


On Sat, Mar 29, 2014 at 2:27 PM, Jeff Garzik <jgarzik@bitpay.com> wrote:

> The comparison with multisig fails to mention that multi-signature
> transactions explicitly define security at the transaction level.
> This permits fine-grained specificity of what a key holder may
> approve.
>
> Shamir is much more coarse-grained.  You reconstitute a private key,
> which may then be used to control anything that key controls.  Thus,
> in addition to Shamir itself, you need policies such as "no key
> reuse."
>
> My first impression of Shamir many moons ago was "cool!" but that's
> since been tempered by thinking through the use cases.  Shamir has a
> higher D.I.Y. factor, with a correspondingly larger surface of
> things-that-could-go-wrong, IMO.
>
> (None of this implies making an informational BIP lacks value; I'm all
> for an informational BIP)
>
>
>
>
> On Sat, Mar 29, 2014 at 7:54 AM, Chris Beams <chris@beams.io> wrote:
> > Enlightening; thanks, Matt. And apologies to the list for my earlier
> inadvertent double-post.
> >
> > On Mar 29, 2014, at 12:16 PM, Matt Whitlock <bip@mattwhitlock.name>
> wrote:
> >
> >> On Saturday, 29 March 2014, at 10:08 am, Chris Beams wrote:
> >>> Matt, could you expand on use cases for which you see Shamir's Secret
> Sharing Scheme as the best tool for the job? In particular, when do you see
> that it would be superior to simply going with multisig in the first place?
> Perhaps you see these as complimentary approaches, toward defense-in-depth?
> In any case, the Motivation and Rationale sections of the BIP in its
> current form are silent on these questions.
> >>
> >> I have added two new sections to address your questions.
> >>
> >> https://github.com/whitslack/btctool/blob/bip/bip-xxxx.mediawiki
> >
> >
> >
> ------------------------------------------------------------------------------
> >
> > _______________________________________________
> > Bitcoin-development mailing list
> > Bitcoin-development@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/bitcoin-development
> >
>
>
>
> --
> Jeff Garzik
> Bitcoin core developer and open source evangelist
> BitPay, Inc.      https://bitpay.com/
>
>
> ------------------------------------------------------------------------------
> _______________________________________________
> Bitcoin-development mailing list
> Bitcoin-development@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/bitcoin-development
>

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  reply	other threads:[~2014-03-29 13:36 UTC|newest]

Thread overview: 90+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-03-29  8:05 [Bitcoin-development] Presenting a BIP for Shamir's Secret Sharing of Bitcoin private keys Matt Whitlock
2014-03-29  8:34 ` Tamas Blummer
2014-03-29  8:44 ` Tamas Blummer
2014-03-29  8:51   ` Matt Whitlock
2014-03-29  8:54     ` Matt Whitlock
2014-03-29 16:54   ` Matt Whitlock
2014-03-29 17:37     ` Tamas Blummer
2014-03-29  9:08 ` Chris Beams
2014-03-29  9:31   ` Matt Whitlock
2014-03-29 11:16   ` Matt Whitlock
2014-03-29 11:54     ` Chris Beams
2014-03-29 13:27       ` Jeff Garzik
2014-03-29 13:36         ` Mike Hearn [this message]
2014-03-29 13:38           ` Tamas Blummer
2014-03-29 14:10           ` Matt Whitlock
2014-03-29 14:19             ` Jeff Garzik
2014-03-29 14:55               ` Matt Whitlock
2014-03-29 15:04                 ` Mike Hearn
2014-03-29 14:28             ` Watson Ladd
2014-03-29 14:36               ` Gregory Maxwell
2014-03-29 15:01                 ` Matt Whitlock
2014-03-29  9:21 ` Chris Beams
     [not found] <CACsn0ckScTWG4YxNCscxvtdsmcUkxtR2Gi-rdBs2HCkirPz5rA@mail.gmail.com>
2014-03-29 15:44 ` Matt Whitlock
2014-03-29 16:59   ` Alan Reiner
2014-03-29 17:19     ` Matt Whitlock
2014-03-29 17:52       ` Alan Reiner
2014-03-29 18:00         ` Matt Whitlock
2014-03-29 18:08           ` Alan Reiner
2014-03-29 18:10             ` Matt Whitlock
     [not found]               ` <CAAt2M18j7bGDsKouVw+e4j+FMiJ4vK6-sx+nrkwHyiKLqiH7Jg@mail.gmail.com>
2014-03-29 19:34                 ` Natanael
2014-04-04  2:38               ` Jeff Garzik
2014-03-29 18:16         ` Tamas Blummer
2014-03-29 18:41           ` Alan Reiner
2014-03-29 17:28     ` Roy Badami
2014-03-29 17:42       ` Matt Whitlock
2014-03-29 17:51         ` Roy Badami
2014-03-29 17:28   ` devrandom
     [not found]   ` <1396113933.8809.91.camel@mimiz>
2014-03-29 17:38     ` Matt Whitlock
2014-03-29 17:46       ` Gregory Maxwell
2014-03-29 19:49         ` Tamas Blummer
2014-03-29 17:48       ` devrandom
2014-03-29 17:51         ` Matt Whitlock
2014-03-29 17:56           ` devrandom
2014-04-03 12:41 Nikita Schmidt
2014-04-03 21:42 ` Matt Whitlock
2014-04-04 13:51   ` Nikita Schmidt
2014-04-04 14:14     ` Gregory Maxwell
2014-04-04 16:05       ` Matt Whitlock
2014-04-04 16:25         ` Gregory Maxwell
2014-04-04 16:36           ` Matt Whitlock
2014-04-04 17:08             ` Gregory Maxwell
2014-04-04 17:16               ` Matt Whitlock
2014-04-04 17:51                 ` Gregory Maxwell
2014-04-04 18:53                   ` Matt Whitlock
2014-04-04 16:03     ` Matt Whitlock
2014-04-08  0:33       ` Nikita Schmidt
2014-04-08  0:38         ` Gregory Maxwell
2014-04-08  1:46           ` Matt Whitlock
2014-04-08  2:07             ` Gregory Maxwell
2014-04-08 11:52               ` Matt Whitlock
2014-04-10 22:31                 ` Nikita Schmidt
2014-04-22  8:06                   ` Jan Møller
2014-04-22  8:11                     ` Matt Whitlock
2014-04-22  8:27                       ` Jan Møller
2014-04-22  8:29                         ` Matt Whitlock
2014-04-22  8:39                           ` Jan Møller
2014-04-22  8:43                             ` Matt Whitlock
2014-04-22  8:51                               ` Jan Møller
2014-04-22  9:13                             ` Matt Whitlock
2014-04-22 11:50                               ` Justin A
2014-04-22  8:35                       ` Matt Whitlock
2014-04-22  8:39                         ` Tamas Blummer
2014-04-22  8:40                           ` Matt Whitlock
2014-04-22  8:43                             ` Tamas Blummer
2014-04-22  8:47                               ` Matt Whitlock
2014-04-22  8:50                                 ` Tamas Blummer
2014-04-22 15:32                           ` Mark Friedenbach
2014-04-22 15:49                             ` Tamas Blummer
2014-04-22 17:03                               ` Mark Friedenbach
2014-04-22 17:07                               ` Jan Møller
2014-04-22 18:29                                 ` Tamas Blummer
2014-04-22 18:46                                   ` Gregory Maxwell
2014-04-23  5:33                                     ` Tamas Blummer
2014-04-23  6:16                                       ` Gregory Maxwell
2014-05-05 19:36                                         ` Nikita Schmidt
2014-05-12 12:09                                           ` Jan Møller
2014-08-14 19:23                                             ` Nikita Schmidt
2014-04-22 13:37                       ` Nikita Schmidt
2014-04-22  8:15                     ` Gregory Maxwell
2014-04-22  8:49                       ` Jan Møller

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