Subject: Re: [bitcoindev] BIP39 Extension for Manual Seed Phrase Creation

From: Kyle Honeycutt <[email-masked]>
Date: Fri, 23 May 2025 07:29:27 -0700

Respectfully, a "black box" is not trusted to generate mnemonic
passphrases, the standard is well-defined and generally followed across
wallets.

https://github.com/bitcoin/bips/blob/master/bip-0039.mediawiki#Generating_the_mnemonic

Users can create their own mnemonics in a trustless way following the BIP39
standard published in 2013.

Using any entropy source a user can perform a SHA256 hash on the entropy to
get a 256 bit string, then convert that to binary. Perform another SHA256
hash on the binary, take the first 8 bits and solve for checksum and then
solve the rest of mnemonic words.

On Fri, May 23, 2025, 6:15 AM Eric Kvam <[email-masked]> wrote:

> *Motivation*
> Make it easy for users to manually create their seed phrase so that they
> don't have to trust a "black box" and allow for encoding derivation path in
> seed phrase to simplify recovery
>
> *How*
> Use every eighth word from the wordlist to generate 16 word phrases with
> 128 bits of entropy (no checksum).  The most significant eight bits of each
> word are used as entropy.  The least significant three bits of each word
> specify the derivation path.
>
>    - *000* Derivation Path Not Specified
>    - *001* m/44'/0'/0'
>    - *010* m/49'/0'/0'
>    - *011* m/84'/0'/0'
>    - *100* m/48'/0'/0'/2'
>    - *101* m/86'/0'/0'
>
> Up to seven derivation paths can be specified if all words have the same
> least significant bits.  If the least significant bits of each word vary,
> there are 48 bits that can be used to encode meta-data.  As long as
> meta-data is limited to certain allowable values, this provides a mechanism
> for error detection, similar to a checksum.
>
> *Benefits of Suggested Implementation*
>
>    - The word length determines how the seed phrase should be
>    interpreted.  User only needs to know how many words they have and how many
>    words the wallet supports to check for compatibility with this extension
>    - Uses same wordlist to represent the same entropy as a 12 word phrase
>    (could be a revision to BIP39 instead of a new BIP)
>    - Manual procedure is very simple, each derivation path can use a
>    shortened 256 word list which enjoys improved alphabetical separation of
>    words
>    - May prevent naive word selections which aren't limited to every
>    eighth word (similar to what checksum does)
>    - Can be extended further.  For example, a 32 word phrase with the
>    same entropy as a 24 word phrase could also be added.  We can keep adding
>    formats with unique word length and keep adding uses for the meta data as
>    needed.
>
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