Hi Brooks,

I've been already thinking about eat -> cat typing mistake. Actually there may be simplier solution than having wordlist with duplicated words. Because there's already a mapping of similar characters in the source code (currently only in unit test, but it can be moved), when user type a word which isn't in wordlist, application may try to use such mapping to find a combination which actually is in the mapping. This may be disambiguous in some cases, but giving a choice between few words may be better than hard fail. And it is actually quite easy to implement. Although I think application can do such smart suggestions and help user to recover badly written mnemonic, I don't think it is necessary to standardize such method directly into BIP. It may or may not be implemented by developers and it is just nice to have feature.

Example:

user type ear, but it isn't in wordlist.

Regards the mapping,

E is similar to A, C, F, O

A is similar to E, C, O

R is similar to B, P, H

So application can calculate combinations of possible characters:

a) when app consider than the the user mistyped only one character

AAR, CAR, FAR, OAR

EER, ECR, EOR

EAB, EAP, EAH

b) when app consider than user maybe mistyped more characters, it may do full combination matrix

AEB,  ACB, AOB,  ... OEH, OCH, OOH

and then ask user to select only these combinations which are actually presented in the wordlist. In this particular case it may be only CAR or FAR (both cannot be in the wordlist because of rules in similarity).

Marek

On Fri, Nov 1, 2013 at 9:14 PM, Brooks Boyd <boydb@midnightdesign.ws> wrote:

I was inspired to join the mailing list to comment on some of these discussions about BIP39, which I think will have great use in the Bitcoin community and outside it as a way to transcribe binary data.

The one thought I had as the discussions about similar characters are resulting in culling words from the list, is that it only helps to validate input, not help the user if it is incorrect.

For example, if both "cat" and "eat" were in the word list, and someone wrote down "eat", but later mis-translated it and put "cat" back into translator, the result would be a checksum error; "cat" is a different number, so the checksum would fail.

As it currently stands, "cat" would not be a valid word ("eat" is the real word, and no other number is "cat"), so the translator can throw a different error which is more helpful (i.e. "'cat' isn't a valid word choice), but still doesn't get the user to the proper translation.

What about if the wordlist included those "words that are so similar to each other that we only kept one of them" and had them all refer to the same number? I propose the wordlist have the possibility of multiple words on a single line, with the first word on the line being the "primary" or "real" word to be used, with the other similar words be included so that a translation program if it wanted to assist the user could fix their input for them (verbosely or not), along the lines of "'cat' isn't a valid word choice; assuming you meant 'eat', which is valid". You might still hit a checksum error if that similar word is still the wrong word, but as it stands now, I know you culled a bunch of words from the wordlist as "too similar", but if I want to try and help the user fix a bad input, I need to write a translation program with a full english dictionary alongside the BIP39 dictionary.

I'd be willing to create a pull request for such an update, but before I delve into that, does this sound like a good idea? I could see it devolving into a slippery slope if every number in the 2048 set had a dozen word variations (misspellings, similar words, slang terms for the real word, etc.) which could get confusing of how similar is similar enough to be added as an alternate, and the standard would need to be clear that when translating binary to words, you only use the "main" word for that row, not any of the variations.

MidnightLightning

 
> I've just pushed updated wordlist which is filtered to similar characters taken from this matrix.
> BIP39 now consider following character pairs as similar:
>         similar = (
>             ('a', 'c'), ('a', 'e'), ('a', 'o'),
>             ('b', 'd'), ('b', 'h'), ('b', 'p'), ('b', 'q'), ('b', 'r'),
>             ('c', 'e'), ('c', 'g'), ('c', 'n'), ('c', 'o'), ('c', 'q'), ('c', 'u'),
>             ('d', 'g'), ('d', 'h'), ('d', 'o'), ('d', 'p'), ('d', 'q'),
>             ('e', 'f'), ('e', 'o'),
>             ('f', 'i'), ('f', 'j'), ('f', 'l'), ('f', 'p'), ('f', 't'),
>             ('g', 'j'), ('g', 'o'), ('g', 'p'), ('g', 'q'), ('g', 'y'),
>             ('h', 'k'), ('h', 'l'), ('h', 'm'), ('h', 'n'), ('h', 'r'),
>             ('i', 'j'), ('i', 'l'), ('i', 't'), ('i', 'y'),
>             ('j', 'l'), ('j', 'p'), ('j', 'q'), ('j', 'y'),
>             ('k', 'x'),
>             ('l', 't'),
>             ('m', 'n'), ('m', 'w'),
>             ('n', 'u'), ('n', 'z'),
>             ('o', 'p'), ('o', 'q'), ('o', 'u'), ('o', 'v'),
>             ('p', 'q'), ('p', 'r'),
>             ('q', 'y'),
>             ('s', 'z'),
>             ('u', 'v'), ('u', 'w'), ('u', 'y'),
>             ('v', 'w'), ('v', 'y')
>         )
> Feel free to review and comment current wordlist, but I think we're slowly moving forward final list.
> slush

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