Re: [bitcoindev] [bitcoin-dev] Proposal discussion: BIP39 native-language display wordlists

[Daniel Osemberg <daniosemberg@gmail.com>]

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Hey Conduition,

Thank you, this is a very useful way to frame the problem.

I agree that the ambiguity must be handled seriously, but I am not sure
that changing the word count, wordlist size, or encoding is the right
direction for this proposal.

The goal of this proposal is not to create a new seed phrase format. The
goal is to define fixed, independent display wordlists that map
deterministically to the canonical English BIP39 word indexes.

In this model, English BIP39 remains the canonical recovery form. The
localized phrase is a wallet-level display/input convention, not a new
entropy encoding scheme and not a replacement for BIP39.

The existing non-English BIP39 wordlists are still relevant for anyone who
created a wallet using those lists. I do not have exact data on how widely
they are used, but it is reasonable to assume they have been used by some
wallets and users. Therefore, any wallet that wants to support both legacy
non-English BIP39 mnemonics and this display-wordlist convention must be
able to distinguish between them explicitly.

That distinction is required regardless of this proposal. Today, a wallet
may already need to distinguish between English BIP39, legacy non-English
BIP39, Electrum seeds, SLIP39, BIP39 with or without passphrase, and other
wallet-specific recovery formats. A seed phrase without context can already
be ambiguous in practice.

For that reason, I think the safer requirement is not to change the
encoding, but to make the restoration mode explicit and prevent silent
interpretation.

A compatible wallet should:

   1. Treat English BIP39 as the canonical form.
   2. Treat TZUR-style localized wordlists as separate fixed display lists,
   not as existing BIP39 language lists.
   3. Never automatically reinterpret a legacy non-English BIP39 mnemonic
   as a mapped display mnemonic.
   4. Clearly label import and export modes.
   5. Always allow the user to view and export the canonical English BIP39
   phrase.
   6. Include stable wordlist identifiers, such as language code, version,
   and hash of the exact wordlist file.

I agree that using disjoint wordlists, or at least avoiding overlap with
existing BIP39 wordlists where possible, can reduce the chance of
confusion. That is a good design constraint for the display lists.

But changing the number of words or changing the encoding would move the
proposal away from being a BIP39-compatible display/input layer and toward
being a new recovery phrase format. That seems like a different proposal
with different compatibility tradeoffs.

So I think the right rule is:

Legacy BIP39 wordlists remain valid for wallets that created them.

The new display lists must be independent, fixed, clearly identified, and
mapped only to canonical English BIP39 indexes.

Wallets that support both must expose the distinction explicitly and must
never guess silently.

Thanks again. This feedback is very helpful, and I will make sure the draft
explains this distinction more clearly.

Best,
Daniel


On Wed, 17 Jun 2026 at 0:18 conduition <conduition@proton.me> wrote:

> Hey Daniel,
>
> For that reason, a wallet implementing this convention should not just see
> “French words” and guess. It should know, or ask, which wordlist mode is
> being used:
>
>
> This is the exact problem I was referring to. Imagine your french uncle
> dies and leaves you a 12 word french seed phrase. You install a BIP39
> wallet and import the seed phrase. The wallet asks you: Is this a BIP39
> seed phrase or a TZUR-translated seed phrase? You don't know what that
> means - all you have is a list of 12 french words. The only thing you can
> do as a user is try both. And if the wallet doesn't ask you at all (because
> maybe it only supports one format or the other), then the wallet happily
> imports the seed without asking and you have no idea the distinction even
> exists.
>
> A seed phrase is supposed to contain all the necessary information to
> recover a wallet, either explicitly in its encoded payload, or implicitly
> in its format. That way a user doesn't have to record or remember any other
> extraneous meta-information - Just the seed phrase.
>
> To make your translated wordlists work like this and fix the ambiguity, I
> would recommend you consider changing the encoding or the format to ensure
> a TZUR-translated display phrase cannot be interpreted as a BIP39
> non-english seed phrase. So for instance, using a different number of
> words. Or use wordlists disjoint from BIP39, so that the probability of a
> random TZUR phrase containing at least one non-BIP39 word is overwhelming.
>
> One clean way to do both would be to increase the size of the TZUR
> wordlists. For instance, instead of encoding 12 words with 11 bits per
> word, you might encode *11 words* with 12 bits per word - the exact same
> number of bits are encoded in both cases. To map the phrase back to BIP39
> is as simple as changing how those bits are interpreted. Since a
> 4096-length word list would be double the size of a BIP39 wordlist, it
> *must* include at least 2048 words not present in the BIP39 wordlists,
> and so a randomly-sampled word has at most a 1 in 2 chance of being in the
> BIP39 wordlist. Thus the chance of all 11 random words just happening to be
> BIP39 words would be at least 1 in 2048. You can (and probably should)
> reduce that probability by reducing the size of the intersection between
> the TZUR and BIP39 wordlists.
>
> You don't have to use those exact numbers either - as long as your
> encoding is able to package all the entropy bits from the equivalent a
> BIP39 seed phrase, it should work. (e.g. 13 words with 10 bits per word,
> encoding 130 bits).
>
> You could use wordlists which have size that isn't a power of two, and use
> some base-x math to reconstruct the entropy as a big unsigned integer.
>
> You could make your wordlists shorter instead of longer, though you'd need
> to be careful to minimize the overlap with BIP39 wordlists.
>
> You could use a different word list for specific word indexes, e.g. the
> first word *must* be a non-bip39 word, and so it encodes less information
> but guarantees the phrase can't be misinterpreted as BIP39.
>
> Anyways just some ideas. Hope it comes in handy.
>
> regards,
> conduition
> On Saturday, June 13th, 2026 at 9:46 AM, Daniel Osemberg <
> daniosemberg@gmail.com> wrote:
>
> Hi conduition,
>
> Thank you for the thoughtful feedback. I agree that ambiguity is the main
> issue any proposal like this has to handle carefully.
>
> To clarify the design: TZUR display wordlists are not meant to replace or
> reinterpret existing BIP39 wordlists. They are separate, index-parallel
> display wordlists whose purpose is to render and accept a user-facing
> mnemonic in another language while keeping the canonical English BIP39
> mnemonic as the seed of record.
>
> So the derivation path for a TZUR display mnemonic is always:
>
> localized TZUR display words → word indices → canonical English BIP39
> words → standard BIP39 checksum validation → standard PBKDF2 → standard
> BIP32/BIP84 derivation
>
> The localized words themselves are never passed directly into PBKDF2. Only
> the canonical English mnemonic is.
>
> Your French example is exactly the edge case that needs to be explicit. A
> legacy French BIP39 mnemonic and a TZUR French display mnemonic are not the
> same thing. They are two different encodings that may use the same human
> language, and they must not be silently treated as interchangeable.
>
> For that reason, a wallet implementing this convention should not just see
> “French words” and guess. It should know, or ask, which wordlist mode is
> being used:
>
>    1.
>
>    Legacy BIP39 French wordlist
>    2.
>
>    TZUR French display wordlist
>    3.
>
>    Canonical English BIP39
>
> The reference design also includes stable wordlist identifiers: language
> code, version, and SHA256 of the exact wordlist file. A wallet can persist
> that metadata alongside the wallet, and use it during restore to avoid
> ambiguity. But for maximum portability, the wallet should always show the
> canonical English mnemonic as the universal recovery form.
>
> So I think your concern is valid. The safe rule is: never auto-detect
> between legacy non-English BIP39 and TZUR display lists when both exist.
> Make the mode explicit, keep the English mnemonic available, and treat the
> display mnemonic as a UX layer rather than a new seed derivation scheme.
>
> Regards,
> Daniel
>
> On Saturday, June 13, 2026 at 7:36:05 PM UTC+3 conduition wrote:
>
>> Hey Daniel,
>>
>> So basically this would allow a user to translate an english language
>> BIP39 seed phrase to/from other languages, insured by the knowledge that it
>> be converted back if needed for compatibility with english-only BIP39
>> wallets.
>>
>> Neat idea. This is how BIP39 should've been done originally. Today, a
>> BIP39 seed derives a different master key depending on what language is
>> used to encode the source entropy, which was arguably a mistake because it
>> breaks compatibility between implementations written for different locales,
>> and incentivizes everyone to use seeds of the same language so that they're
>> maximally compatible (which is exactly what happened).
>>
>> I worry your proposal here might cause confusion if introduced today
>> though. Say you are given a french language 12-word seed phrase. Do you map
>> the word indices to english and then run PBKDF2 with your algorithm? Or do
>> you run PBKDF2 on the french version as specified in the original BIP39?
>>
>> There would need to be a clear way for humans and software to distinguish
>> between a "locale-mapped seed phrase" using your spec, and a legacy french
>> BIP39 seed phrase, so they know how to derive the correct master key.
>>
>> I guess one could argue that non-english BIP39 seeds are so uncommon that
>> you could safely assume the former, but still it leaves open an unfortunate
>> ambiguity which could lead to lost funds in some cases.
>>
>> What do you think of this?
>>
>> regards,
>> conduition
>> On Saturday, June 13th, 2026 at 12:04 PM, Daniel Osemberg <
>> danios...@gmail.com> wrote:
>>
>> Hi list,
>>
>> I would like to ask for early feedback on an idea before attempting any
>> formal BIP submission.
>>
>> The proposal is a display/input layer for BIP39 recovery phrases in
>> additional native languages.
>>
>> The important constraint is that this does not change the BIP39
>> cryptographic flow. The canonical mnemonic remains the existing BIP39
>> English wordlist, and PBKDF2 is still performed on the canonical English
>> form.
>>
>> The native-language lists are index-paired to the English BIP39 wordlist.
>> In other words, each native word maps to the same 0-2047 index as the
>> corresponding English BIP39 word. Wallets could display or accept the
>> native-language form for UX purposes, but internally normalize back to the
>> canonical English mnemonic before seed generation.
>>
>> Motivation:
>>
>> Many users around the world are asked to back up and restore Bitcoin
>> wallets using English recovery words, even when English is not their native
>> language. This creates UX risk, spelling mistakes, misunderstanding, and
>> lower confidence during backup and recovery.
>>
>> This proposal tries to improve multilingual recovery UX while keeping
>> compatibility with existing BIP39 behavior.
>>
>> This is not:
>>
>> A new seed scheme
>> A replacement for BIP39
>> A new cryptographic standard
>> A change to PBKDF2 input
>> A wallet-specific format
>>
>> It is intended as a display/input convention for wallets that want to
>> support native-language recovery UX while preserving canonical BIP39
>> compatibility.
>>
>> A draft implementation and wordlists are here:
>>
>> https://github.com/osem23/bip39-wordlists-tzur
>>
>> I would appreciate feedback on:
>>
>> Whether this idea is appropriate for the BIP process at all
>> Whether it should be considered informational rather than standards-track
>> Whether the index-paired approach creates hidden risks
>> Whether wallet developers see practical value in this
>> How native-speaker review and normalization rules should be handled
>> Whether there is prior work I should study before continuing
>>
>> Thank you,
>> Daniel
>>
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