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Date: Fri, 24 Jan 2014 17:47:21 +0100
From: Thomas Voegtlin <thomasv1@gmx.de>
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Subject: Re: [Bitcoin-development] BIP0039: Final call
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Le 24/01/2014 10:05, Peter Todd a écrit :
> On Tue, Jan 21, 2014 at 01:00:43AM +0100, Thomas Voegtlin wrote:
>> Hi slush,
>>
>> Thank you for your new proposal; it seems to be a compromise.
>>
>> @Christophe Biocca:
>> If the wordlist becomes part of the standard, then we will run into
>> problems of collisions once users ask for wordlists in every language.
>>
>> IMO the right approach is to implement checksums that do not depend
>> on the wordlist (eg the 'brute force' method, Hash(mnemonic||1) mod
>> 2^k == 0 )
>> this would also allow us to implement sipa's variable stretching proposal.
>>
>> I understand this is not possible because of the computational
>> requirements of devices such as trezor.
> Is it? Surely the trezor can bruteforce, say, 8 bits == 0. How many
> SHA256/sec can the trezor hardware do? Generating your seed is a
> one-time thing after all - that taking 10-30s doesn't seem like a big
> deal to me.
>
> Even a 1/256th "checksum" will really cut down on the number of mistakes
> made and money lost.

slush, correct me if I'm wrong, but I don't think that's the only reason:
They want to generate a seed by combining entropy from the trezor device 
and from the user's computer;
In addition, they want the computer to be able to check that the seed 
actually was derived from the entropy it provided, using only a master 
public key (the computer does not have access to the seed)

This is why they designed bip39 that way.

I think the new bip39 proposal could be used in Electrum as an option 
for trezor, but I am reluctant to make it default, because it imposes 
its own dictionary.