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From: "'Rama Gan' via Bitcoin Development Mailing List" <bitcoindev@googlegroups.com>
To: Andrew Poelstra <apoelstra@wpsoftware•net>
Cc: "bitcoindev@googlegroups.com" <bitcoindev@googlegroups.com>
Subject: Re: [bitcoindev] Penlock, a paper-computer for secret-splitting BIP39 seed phrases
Date: Fri, 24 May 2024 10:39:57 +0000	[thread overview]
Message-ID: <EfekwtxUZKN_4z53hjqo7lXhcMDaRHlIC-EOWNjcpL_cJgeYPa1-_1g0b6PxLZPEL0oj7YAXEWK7yg7WiEHH2FkIk7WHIFGwjMB1zoxYb6M=@proton.me> (raw)
In-Reply-To: <ZkZBSriGn96GDLg-@camus>

> Ah, I am incorrect. You can put the recovery windows on a slide wheel
> but it needs to use a different ordering than the one used for addition.
> So you would need a second wheel and possibly some relabelling of
> recovery windows.
> 
> I don't see why this is ... it seems that the recovery windows, being
> differences of characters, should follow exactly the same pattern as
> addition (possibly in the opposite direction). So worth investigating.

No, no, you were right, it can be done.

If you want to find the difference between A[2] and D[5], you can place the
pointer on A, find D on the outer ring and the corresponding inner-ring
character will be B[3]. Then, it is possible to write the numerical values under
the first 14 characters as you suggested before. (We only care about the
_shortest_ distance.)

I chose to use a window because it's less "verbose". I didn't want to clutter
the wheel with information that you'd use only once per recovery. (Using the
window is in fact more compact.)

About a header, the problem is that the fast 2-of-M algorithm won't preserve
constant values across shares as Codex32 does. In Penlock, the header
information is simply printed/written on the share instead of being encoded. The
best I can do is to tweak both algorithm so that you can derive the secret and
share's index correctly, by using "-[28]" as the secret's index. (But the secret
is not a point on the line, and the share at X=28 would have a different value,
so that might be more confusing than anything)

-- Rama Gan

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  reply	other threads:[~2024-05-24 10:59 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-05-12 18:04 'Rama Gan' via Bitcoin Development Mailing List
2024-05-13 13:40 ` Andrew Poelstra
2024-05-14 12:03   ` 'Rama Gan' via Bitcoin Development Mailing List
2024-05-14 13:42     ` Andrew Poelstra
2024-05-16  7:43       ` 'Rama Gan' via Bitcoin Development Mailing List
2024-05-16 13:27         ` Andrew Poelstra
2024-05-16 17:24           ` Andrew Poelstra
2024-05-24 10:39             ` 'Rama Gan' via Bitcoin Development Mailing List [this message]
2024-05-24 14:14               ` Andrew Poelstra
2024-05-24 15:02                 ` 'Rama Gan' via Bitcoin Development Mailing List
2024-05-14 12:43 ` 'Rama Gan' via Bitcoin Development Mailing List

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