BIP- & SLIP-0039 -- better multi-language support

   Entropy <=> Mnemonic Sentence => PBKDF2 => BIP-0032 Seed
   Mnemonic Sentence <=> Entropy => PBKDF2 => BIP-0032 Seed
> Date: Wed, 7 Nov 2018 00:16:41 +0800
> From: Weiji Guo weiji.g@gmail•com
> Subject: [bitcoin-dev] BIP- & SLIP-0039 -- better multi-language
> support
>
> Hello everyone,
>
> I just realized that BIP-0039 is language dependent. I was assuming the
> other way till I looked closer. The way the seed is derived from a BIP-0039
> entropy, as is shown below, depends on which language to generate the
> mnemonic sentence:
>
> Entropy <=> Mnemonic Sentence => PBKDF2 => BIP-0032 Seed
>
> Therefore when a user choose a non-English mnemonic code he or she is stuck
> with that language. Meanwhile only a few native languages are supported.
>
> SLIP-0039 does not solve this issue in a user friendly way by providing
> only an English wordlist. That's understandable as it aims to provide SSS
> capability. However those users who do not speak English or recognize
> English words will suffer.
>
> What I am trying to bring to attention of the community is that, no matter
> if we make a new version of BIP-0039, or a new BIP (with SSS support), or
> to enhance SLIP-0039, we really need to address this language issue.
>
> Here are what I propose:
>
> 1.  The mnemonic code should be only a representation of underlying entropy
>     or (pre) master secret, seed, whatever. In this way, the same seed/secret
>     could be displayed in English or in Chinese or other languages. Then there
>     could be 3rd party conversion tools to support translations in case any
>     wallet software or device does not support all specified languages. Now it
>     looks like:
>
>     Mnemonic Sentence <=> Entropy => PBKDF2 => BIP-0032 Seed
>
>
> 2. Given that only 8 languages are supported in BIP-0039, we should allow
> the seed/secret to be represented in decimal numbers, each ranging from 0
> to 2047. So those who cannot find a native language support yet having
> difficulty coping words in other languages could choose to just use numbers.
>
> So far I don't have a preference how this should be implemented. I'd like
> to hear from community first.
>  as it seems bad design to have to fix and maintain a wordlist for every
> The conversion of the mnemonic sentence to a binary seed is completely
>
> Although using a mnemonic not generated by the algorithm described in
1. Run ChecksumCheck
2. If False, hard fail, do not allow seed generation.
> Do you specifically want to support changing the language of seed
> words, while keeping the bip32 root seed they generate unchanged?
> What is the usecase for this?
>
> You mention that BIP39 already supports a few different languages.
> While this is true, many (I would guess most!) wallets only
> support the English wordlist.
> There are doubts even from the authors of the BIP whether it was
> a good idea in the first place to support multiple languages [0].
> I don't find this surprising as it seems bad design to have to fix and
> maintain a wordlist for every language as the checksum depends on it.
> The supported wordlists are effectively a part of the specification,
> and every new list would just make that specification larger.
>
> If changing the language of seeds is not a requirement, then look
> into Electrum seeds. They are language/wordlist agnostic.
>
> Mnemonic Sentence => PBKDF2 => BIP-0032 Seed
>
> The bip32 seed is derived by hashing the normalized mnemonic, and the
> checksum is derived the same way but by using a different cheaper
> hash (single round of HMAC-SHA512; generation grinds until it matches
> a pattern) [1]. For example, "9dk" is a valid segwit electrum seed.
>
>
> [0]:
> https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2018-January/015507.html
> [1]: http://docs.electrum.org/en/latest/seedphrase.html
>
>
> > Date: Wed, 7 Nov 2018 00:16:41 +0800
> > From: Weiji Guo weiji.g@gmail•com
> > Subject: [bitcoin-dev] BIP- & SLIP-0039 -- better multi-language
> > support
> >
> > Hello everyone,
> >
> > I just realized that BIP-0039 is language dependent. I was assuming the
> > other way till I looked closer. The way the seed is derived from a
> BIP-0039
> > entropy, as is shown below, depends on which language to generate the
> > mnemonic sentence:
> >
> > Entropy <=> Mnemonic Sentence => PBKDF2 => BIP-0032 Seed
> >
> > Therefore when a user choose a non-English mnemonic code he or she is
> stuck
> > with that language. Meanwhile only a few native languages are supported.
> >
> > SLIP-0039 does not solve this issue in a user friendly way by providing
> > only an English wordlist. That's understandable as it aims to provide SSS
> > capability. However those users who do not speak English or recognize
> > English words will suffer.
> >
> > What I am trying to bring to attention of the community is that, no
> matter
> > if we make a new version of BIP-0039, or a new BIP (with SSS support), or
> > to enhance SLIP-0039, we really need to address this language issue.
> >
> > Here are what I propose:
> >
> > 1.  The mnemonic code should be only a representation of underlying
> entropy
> >     or (pre) master secret, seed, whatever. In this way, the same
> seed/secret
> >     could be displayed in English or in Chinese or other languages. Then
> there
> >     could be 3rd party conversion tools to support translations in case
> any
> >     wallet software or device does not support all specified languages.
> Now it
> >     looks like:
> >
> >     Mnemonic Sentence <=> Entropy => PBKDF2 => BIP-0032 Seed
> >
> >
> > 2. Given that only 8 languages are supported in BIP-0039, we should allow
> > the seed/secret to be represented in decimal numbers, each ranging from 0
> > to 2047. So those who cannot find a native language support yet having
> > difficulty coping words in other languages could choose to just use
> numbers.
> >
> > So far I don't have a preference how this should be implemented. I'd like
> > to hear from community first.
>
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev@lists•linuxfoundation•org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>
> If more apps would implement to the word of the BIP39 spec, multiple
> languages make sense, but since reality is no one follows the spec (/the
> spec is way too open to interpretation) then expecting every app to load
> every language is unreasonable.
>
> Electrum actually handles BIP39 recovery the way the BIP specifies. I can
> restore random strings if I want, and it warns me, and I can ignore it if I
> wish.
> On Fri, Nov 09, 2018 at 02:17:30PM +0900, Jonathan Underwood via
> bitcoin-dev wrote:
> > If more apps would implement to the word of the BIP39 spec, multiple
> > languages make sense, but since reality is no one follows the spec (/the
> > spec is way too open to interpretation) then expecting every app to load
> > every language is unreasonable.
> >
> > Electrum actually handles BIP39 recovery the way the BIP specifies. I can
> > restore random strings if I want, and it warns me, and I can ignore it
> if I
> > wish.
>
> Electrum mnemonics are not based on BIP39, which is why it can do
> this.
>
> -Neill.
>
>
> Nope.
>
> This is how Electrum treats BIP39 restoring as well, try it out.
>
> -Jon
>
> 2018年11月16日(金) 23:04、Neill Miller さん（neillm@thecodefactory•org）のメッセージ:
>
> > On Fri, Nov 09, 2018 at 02:17:30PM +0900, Jonathan Underwood via
> > bitcoin-dev wrote:
> > > If more apps would implement to the word of the BIP39 spec, multiple
> > > languages make sense, but since reality is no one follows the spec (/the
> > > spec is way too open to interpretation) then expecting every app to load
> > > every language is unreasonable.
> > >
> > > Electrum actually handles BIP39 recovery the way the BIP specifies. I can
> > > restore random strings if I want, and it warns me, and I can ignore it
> > if I
> > > wish.
> >
> > Electrum mnemonics are not based on BIP39, which is why it can do
> > this.
> >
> > -Neill.
> >
> >
   - *English BIP39 seed:*
   ce7618075099c89e986f18dc495daa3be190450ed07bef77d4334a54dbc1cd7e205797ffed2615ac0999a5d691f65bf316e2cdbfd2c9d7d90b03e77ff1e6a6f5
   - *Spanish BIP39 seed*:
   9f164de0fb09af51b5831886e424d6d2479d49b5e5a1b28f5c09467ea36089b144cd94bb9b636b3c27ccff96a8958e5b7ce43cf1dea81423fc66fa7fef0aea2c
      - The multiple BIP39 seeds per language lend some similarities to
BIP44 multi-account, so perhaps this can be an advantage, depends on how it
is applied in UI/UX's (compared to having one BIP39 seed regardless of
language, for a given initial entropy).
      - There is perhaps an opportunity to add greater detail to the BIP39
spec in terms of standards/best-practices for computing checksum values, as
some software may be hashing bits, versus hashing bytes, or hashing the
entropy as a hex string, etc.. for a given entropy, which will result in
different checksum values for the same "valid" mnemonic, that might not be
"valid" in another wallet which may format the data differently before
hashing to compute the checksum.
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   Entropy <=> Mnemonic Sentence => PBKDF2 => BIP-0032 Seed
   Mnemonic Sentence <=> Entropy => PBKDF2 => BIP-0032 Seed
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> Hi Weiji, and Everyone,
>
> I think this is an important topic so sharing my two cents in case in
> helps: It makes sense for users to know that they can't merely just
> translate a word from one language into another and expect the same
> underlying entropy to be mapped, as the wordlists are not the same (i.e.
> words differ at the same index values across languages).
>
> However, while the words for each language cannot translate directly to
> their equivalent in another language, in terms of entropy (bits), the
> underlying entropy is, in fact, the same, when comparing mnemonics
> generated across languages (see English/Spanish comparison below) when
> sourced from the same initial entropy.
>
> Importantly, the entropy is a pre-image of the resulting mnemonic and
> doesn't change as the language changes, where the only changes are to the
> resulting words which depend on the language chosen, for a given entropy
> string. Ideally, the wallet/software should deal with these nuances, I
> don't think the protocol needs any revision (except for how the BIP39 seed
> is derived, perhaps), even if someone made up their own wordlist, as long
> as the wallet/software has a copy of it to map those words to the
> underlying index values, it's *those underlying index values and the
> entropy they map too is what really matters**. *
>
> I fully support the idea for users to back up this pre-image (initial
> entropy) as it can also be used to check the validity of the mnemonic and
> check that it mapped correctly, see Ian Coleman's BIP39 tool which shows
> index values, a feature that I proposed last year and was since
> implemented. Below is an example of how two mnemonics generated with the
> same entropy will produce different BIP39 seeds.
>
> * Example initial entropy of 128 bits +4 bit checksum derived from hash of
> byte array: *
>
> 10001101000 01010100100 11011010000 11100001101 01010001101 00010010001
> 01100000010 10101110100 00100100011 11110000111 01100011010 1100010 (+1110
> checksum)
>
> *In English*: minimum fee sure ticket faculty banana gate purse caught
> valley globe shift
>
> The same initial entropy above (all 132 bits) produces this mnemonic:
>
> *In Spanish*: mercado faja soledad tarea evadir aries gafas peine búho
> tumor gerente reja
>
> And the underlying index values below are the same for both the English
> and Spanish mnemonics above:
>
> Word Indexes: 1128, 676, 1744, 1805, 653, 145, 770, 1396, 291, 1927, 794,
> 1582
>
> *ISSUE AT HAND*:  While the initial entropy is the same, and word indexes
> the same for a given entropy, (i.e. same pre-image), the resulting BIP39
> seed is not the same when comparing the above English mnemonic with its
> Spanish counterpart:
>
>    - *English BIP39 seed:*
>    ce7618075099c89e986f18dc495daa3be190450ed07bef77d4334a54dbc1cd7e205797ffed2615ac0999a5d691f65bf316e2cdbfd2c9d7d90b03e77ff1e6a6f5
>    - *Spanish BIP39 seed*:
>    9f164de0fb09af51b5831886e424d6d2479d49b5e5a1b28f5c09467ea36089b144cd94bb9b636b3c27ccff96a8958e5b7ce43cf1dea81423fc66fa7fef0aea2c
>
>
> *Option 1:* Without changing anything in terms of the entropy
> generation/mapping process in the BIP39 spec, the wallet/client-side
> software would ideally recognize the language and show the corresponding
> index value per wordlist, and reverse-calculate the entropy and then re-map
> it to the language selected.
>
> *Option 2*: Perhaps a revision is needed to how the BIP39 seed is
> generated in the first place, such as by hashing the entropy instead of the
> words. Any thoughts on how viable that could be where the initial entropy
> is fed into the PBKDF2 function and not the words?
>
> *Closing thoughts and tiny checksum nitpick: *
>
>       - The multiple BIP39 seeds per language lend some similarities to
> BIP44 multi-account, so perhaps this can be an advantage, depends on how it
> is applied in UI/UX's (compared to having one BIP39 seed regardless of
> language, for a given initial entropy).
>       - There is perhaps an opportunity to add greater detail to the BIP39
> spec in terms of standards/best-practices for computing checksum values, as
> some software may be hashing bits, versus hashing bytes, or hashing the
> entropy as a hex string, etc.. for a given entropy, which will result in
> different checksum values for the same "valid" mnemonic, that might not be
> "valid" in another wallet which may format the data differently before
> hashing to compute the checksum.
>
>