From: "Peter D. Gray" <peter@coinkite•com>
To: Tobias Kaupat <Tobias@kaupat-hh•de>
Cc: bitcoin-dev@lists•linuxfoundation.org
Subject: Re: [bitcoin-dev] Encryption of an existing BIP39 mnemonic without changing the seed
Date: Thu, 6 May 2021 08:56:37 -0400 [thread overview]
Message-ID: <20210506125637.GF1239@coinkite.com> (raw)
In-Reply-To: <CAPyCnfvqVT00C2TZ86GXf856jNJqPXY0duRa1CfdCqC0ecC6xA@mail.gmail.com>
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Hi Tobias.
The most recent release of Coldcard now offers "Seed XOR" to solve
similar problems. It allows any numbers of standard BIP-39
compatible seed phrases to be bitwise XOR'ed together to make a new seed.
Coldcard can split an existing seed into 2, 3 or 4 new phrases, or
you can take your existing seed phrase, and XOR-in a new seed phrase
to arrive at a new random seed phrase (and wallet).
More details about this feature at: <https://seedxor.com>
Best part is XOR is simple enough that the split or combine operation can
be worked out by hand on paper. (We even made a worksheet for this.)
The checksums on each of the XOR parts protects the final result, and
each "part" is a fully functional decoy wallet.
Hope that helps!
On Wed, May 05, 2021 at 07:32:05PM +0200, Tobias Kaupat wrote:
> Hi all,
> I want to start a discussion about a use case I have and a possible
> solution. I have not found any satisfying solution to this use case yet.
>
> *Use case:*
> An existing mnemonic (e.g. for a hardware wallet) should be saved on a
> paper backup in a password encrypted form. The encrypted form should be a
> mnemonic itself to keep all backup properties like error correction.
>
> *Suggested solution:*
> 1) Take the existing mnemonic and extract the related entropy
> 2) Create a SHA526 hash (key) from a user defined password
> 3) Use the key as input for an AES CTR (empty IV) to encrypt the entropy
> 4) Derive a new mnemonic from the encrypted entropy to be stored on a paper
> backup
...
> *Existing solutions*
> One solution I found is "Seedshift" which can be found here:
> https://github.com/mifunetoshiro/Seedshift
>
> But I consider it less secure and I would like to suggest a solution based
> on provably secure algorithms rather than a "rot23 derivation". Also using
> a date as password seems not very clever to me.
>
> Kind regards
> Tobias
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next prev parent reply other threads:[~2021-05-06 13:01 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-05 17:32 Tobias Kaupat
2021-05-06 12:56 ` Peter D. Gray [this message]
2021-05-06 13:19 ` Erik Aronesty
2021-05-06 14:10 ` Tobias Kaupat
2021-05-08 22:49 ` yanmaani
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