[bitcoin-dev] Card Shuffle To Bitcoin Seed

Alan Evans thealanevans at gmail.com
Wed Feb 6 13:51:59 UTC 2019


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On Wed, 6 Feb 2019 at 09:48, Alan Evans <thealanevans at gmail.com> wrote:

> It's not quite enough to just do SHA512, you missed out this condition
> (incredibly rare as it is):
>
> > In case IL is 0 or ≥n, the master key is invalid.
>
> Also I can't see how I would use this to seed a hardware wallet that
> requires a BIP39 seed as mentioned in your abstract.
>
> For both of those reasons, you may want to just invent/formalize a scheme
> that takes Cards -> Entropy.
> From that Entropy one can generate BIP39, and non-BIP39 fans can just
> continue, generate and store their root xprv.
>
> Prior art: Note that Ian Coleman's BIP39 site already supports Cards (and
> Dice), see the logic here:
> https://github.com/iancoleman/bip39/blob/master/src/js/entropy.js
>
> [image: image.png]
>
> Note it detected "full deck". It also calculates the Total Bits of Entropy
> and can handle card replacement and multiple decks.
>
> PS, you're a bit out on your entropy calculation, log2(52!) ~= 225.58
> bits, not 219.
>
>
> On Tue, 5 Feb 2019 at 02:08, Devrandom via bitcoin-dev <
> bitcoin-dev at lists.linuxfoundation.org> wrote:
>
>> I would suggest 50+ 6-sided dice rolls, giving about 128 bits of
>> entropy.  Compared to a shuffle, it's easier to be sure that you got the
>> right amount of entropy, even if the dice are somewhat biased.
>>
>>
>> On Mon, Feb 4, 2019 at 2:33 PM James MacWhyte via bitcoin-dev <
>> bitcoin-dev at lists.linuxfoundation.org> wrote:
>>
>>>
>>> James
>>>
>>>
>>> On Sun, Feb 3, 2019 at 10:27 AM Ryan Havar via bitcoin-dev <
>>> bitcoin-dev at lists.linuxfoundation.org> wrote:
>>>
>>>> Conveniently a shuffled deck of cards also can serve as a physical
>>>> backup which is easy to hide in plain sight with great plausible
>>>> deniability.
>>>>
>>>
>>> To make sure someone doesn't play with your cards and mix up the order,
>>> use a permanent marker to draw a diagonal line on the side of the deck from
>>> corner to corner. If the cards ever get mixed up, you can put them back in
>>> order by making sure the diagonal line matches up.
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>
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