Ok, I see your point here, and I was referring to rebuilding from entropy -- which as you noted is not a real world usage. It is a useful implementation test though and at the very least the existing test vectors would need to be regenerated with each word list change.
I recently added BIP39 to libbitcoin and our implementation would fail with an arbitrarily new word list because we validate the user provided word list before converting it to a seed (i.e. we check that the encoded entropy/checksum line up and warn the user if that's not the case to distinguish a rubbish word list from a BIP39 mnemonic -- as referenced in the BIP). You're correct that we could use rubbish words, but at the moment it's not allowed there. By removing that validating 'restriction', I agree with you that word lists have no need to be fixed. But realistically, we still don't allow completely arbitrary words to be used because I don't see the word lists changing too often, nor implementations storing word lists of all words and languages. Thanks for clarifying, -Neill. On Thu, Mar 12, 2015 at 04:21:59AM +0000, Thy Shizzle wrote: > "I agree that it's true that a static wordlist is > required once people have started using BIP39 for anything real and > changing the word lists will invalidate any existing mnemonics" > ^ This is incorrect I think Neill, the reason is that the only thing that > happens when you change the wordlist is that entropy points to different > words. But remember, entropy is disposed. Yes in my code I allow for the > keeping of entropy etc, it also lets me "hot swap" between different language > wordlists etc but in real world implementation the entropy is forgotten and > not stored. So changing the wordlist merely allows new mnemonic phrases to be > generated but it has a nil impact on previously generated mnemonics UNLESS > you are trying to rebuild from entropy but you wouldn't do that. You would be > rebuilding from the Mnemonic in real world scenario. You really can have a > word list of total rubbish in BIP39 as long as it is 2048 words long that is > all! If you input the mnemonic made out of rubbish words so for e.g "uyuy > jkjasd sdsd sdsdd yuuyu sdsds iooioi sdasds uyuyuy sdsdsd tyyty rwetrtr" and > no matter what BIP39 implementation you put it in, it will always generate > the same seed bytes thus allowing for complete and universal seed derivation > without any reliance on word list. The word list is merely to generate a > mnemonic, after that it has no role in seed generation so you can change it > at anytime and it will never effect future mnemonics. > > On Thu, Mar 12, 2015 at 02:16:38AM +0000, Thy Shizzle wrote: > > That's disappointing the Electrum 2.0 doesn't use BIP39. > > Agreed, but I don't know the full background on this. > > > Changing the wordlist in the future has ZERO effect on derived seed, > > whatever mnemonic you provide will always generate the same seed, BIP39 is > > not mapping the words back to numbers etc to derive seed. > > That's true for generating new mnemonics (i.e. same entropy can > generate any combinations of words), but not for converting a mnemonic > to a seed (i.e. a specific wordlist/passphrase should always generate > the same seed). I agree that it's true that a static wordlist is > required once people have started using BIP39 for anything real and > changing the word lists will invalidate any existing mnemonics (unless > your 'new' wordlist simply substitutes one word for another and the > index mapping is made public ... which means it's not really an > arbitrary word list). > > > Version is something that can be dealt with after the fact, hopefully > > standardised (curious why didn't you work with the BIP39 to insert version > > instead of do something different to BIP39?) > > So most of what you are suggesting as problems are not. > > I don't see how this can work given the BIP39 spec as it is today > (there's simply no room for a version in the bits). I do think > versioning would be nice, but as of now, I'm in the camp that thinks > complete wallet interoperability is a bit of a myth -- so long as you > can fundamentally move into/out of wallets at will. > > -Neill. > > > As for the common words between languages, I have discussed this with the > > provider of the Chinese wordlists as they shared some words between > > simplified and traditional, but I found it easy to look for a word in the > > mnemonic that is unique to that language/wordlist and so straight away you > > can determine the language, remembering you get minimum 12 goes at doing > > that :) > > Also then I asked myself, do we really care about detecting the language? > > Probably not because we don't need to use the wordlist ever again after > > creation, we literally accept the mnemonic, normalise it then hash it into > > a seed. From what I'm reading, Electrum 2.0 really should have BIP39, it > > would take almost no effort to put it in and I think you should do that :) > > I don't have any interest in BIP39 other than it being a standard. I think > > TREZOR may have an interest in it? > > Thomas V: > > "Thanks Mike, and sorry to answer a bit late; it has been a busy couple > > of weeks. > > > > You are correct, a BIP39 seed phrase will not work in Electrum, and vice > > versa. It is indeed unfortunate. However, I believe BIP39 should not be > > followed, because it reproduces two mistakes I did when I designed the > > older Electrum seed system. Let me explain. > > > > The first problem I have with BIP39 is that the seed phrase does not > > include a version number. > > > > Wallet development is still in an exploratory phase, and we should > > expect even more innovation in this domain. In this context, it is > > unwise to make decisions that prevent future innovation. > > > > However, when we give a seed phrase to users, we have a moral obligation > > to keep supporting this seed phrase in future versions. We cannot simply > > announce to Electrum users that their old seed phrase is not supported > > anymore, because we created a new version of the software that uses a > > different derivation. This could lead to financial losses for users who > > are unaware of these technicalities. Well, at least, that is how I feel > > about it. > > > > BIP39 and Electrum v2 have a very different ways of handling future > > innovation. Electrum v2 seed phrases include an explicit version number, > > that indicates how the wallet addresses should be derived. In contrast, > > BIP39 seed phrases do not include a version number at all. BIP39 is > > meant to be combined with BIP43, which stipulates that the wallet > > structure should depend on the BIP32 derivation path used for the wallet > > (although BIP43 is not followed by all BIP39 compatible wallets). Thus, > > innovation in BIP43 is allowed only within the framework of BIP32. In > > addition, having to explore the branches of the BIP32 tree in order to > > determine the type of wallet attached to a seed might be somewhat > > inefficient. > > > > The second problem I see with BIP39 is that it requires a fixed > > wordlist. Of course, this forbids innovation in the wordlist itself, but > > that's not the main problem. When you write a new standard, it is > > important to keep this standard minimal, given the goal you want to > > achieve. I believe BIP39 could (and should) have been written without > > including the wordlist in the standard. > > > > There are two ways to derive a master key from a mnemonic phrase: > > 1. A bidirectional mapping between words and numbers, as in old > > Electrum versions. Pros: bidirectional means that you can do Shamir > > secret sharing of your seed. Cons: It requires a fixed wordlist. > > 2. Use a hash of the seed phrase (pbkdf). Pros: a fixed wordlist is not > > required. Cons: the mapping isn't bidirectional. > > > > Electrum v1 uses (1). Electrum v2 uses (2). > > > > Early versions of BIP39 used (1), and later they switched to (2). > > However, BIP39 uses (2) only in order to derive the wallet keys, not for > > its checksum. The BIP39 checksum uses (1), and it does requires a fixed > > wordlist. This is just plainly inconsistent. As a result, you have > > neither wordlist flexibility, nor Shamir secret sharing. > > > > Having a fixed wordlist is very unfortunate. First, it means that BIP39 > > will probably never leave the 'draft' stage, until all languages of the > > world have been added. Second, once you add a wordlist for a new > > language, you cannot change it anymore, because it will break existing > > seed phrases; therefore you have to be extremely careful in the way you > > design these wordlists. Third, languages often have words in common. > > When you add a new language to the list, you should not use words > > already used by existing wordlists, in order to ensure that the language > > can be detected. It leads to a first come first served situation, that > > might not be sustainable in the future. > > > > In order to support the old Electrum v1 seeds, all future versions of > > Electrum will have to include the old wordlist. In addition, when > > generating new seed phrases, Electrum now has to avoid collisions with > > old seed phrases, because the old ones did not have a version number. > > This is painful enough, I will not repeat the same errors twice. > > > > Electrum v2 derives both its private keys and its checksum/version > > number using a hash of the seed phrase. This means that wordlists can be > > added and modified in the future, without breaking existing seed > > phrases. It also means that it will be very easy for other wallets to > > support Electrum seedphrases: it requires about 20 lines of code, and no > > wordlist is required." > > > > > > Thomas > > > > > > Le 02/03/2015 16:37, Mike Hearn a écrit : > > > Congrats Thomas! Glad to see Electrum 2 finally launch. > > > > > > > > >> * New seed derivation method (not compatible with BIP39). > > > > > > > > > Does this mean a "12 words" wallet created by Electrum won't work if > > > imported into some other wallet that supports BIP39? Vice versa? This > > > seems > > > unfortunate. I guess if seeds are being represented with 12 words > > > consistently, people will expect them to work everywhere. > > > > > > > ------------------------------------------------------------------------------ > > Dive into the World of Parallel Programming The Go Parallel Website, > > sponsored > > by Intel and developed in partnership with Slashdot Media, is your hub for > > all > > things parallel software development, from weekly thought leadership blogs > > to > > news, videos, case studies, tutorials and more. Take a look and join the > > conversation now. http://goparallel.sourceforge.net/ > > _______________________________________________ > > Bitcoin-development mailing list > > Bitcoinemail@example.com > > Bitcoin-development -- > > | | > > | | | | | | > > | Bitcoin-development --To see the collection of prior postings to the > > list, visit the Bitcoin-development Archives. | > > | | > > | View on lists.sourceforge.net | Preview by Yahoo | > > | | > > | | > > > > > > > > > > > > > ------------------------------------------------------------------------------ > > Dive into the World of Parallel Programming The Go Parallel Website, > > sponsored > > by Intel and developed in partnership with Slashdot Media, is your hub for > > all > > things parallel software development, from weekly thought leadership blogs > > to > > news, videos, case studies, tutorials and more. 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