[Bitcoin-development] Export format for xpub

Levin Keller post at levinkeller.de
Tue Feb 3 09:33:16 UTC 2015


Why even bother with the specific HD scheme such as BIP32  or BIP44. What
are the interesting parameters?

Required:

   - gap limit

Optional:

   - which node of the derivation chain is actually exported (m0' for
   BIP32, m44'0'account' for BIP44)
   - which subnodes are used for external and internal purposes
   - creation date

To import the data in a read only application it is not important which
node one actually gets and in all implementations the subnode of the
exported node "0" is used for external addresses and "1" for internal
addresses.

There is no usecase to export any higher node than m0' in BIP32 or
m44'0'account' as one can only derive any child nodes of the higher nodes *with
the private master key*. As for lower nodes (like further down the path)
there is also no need to export because in all implementations today they
will only give around half of the used addresses.

So I think a more general but very useful export scheme would be:

bitcoin-pub-export:xpub[gibberish]?gaplimit=[number]&path=[path in
derivation tree]&subchains=[numbers]&creationdate=[unixtimestamp]

Why not have more descriptive parameters? Saving on data?

I am a big fan of unix timestamps. Would vote for Andreas' format on the
creation date.

Cheers

Levin

2015-02-03 1:22 GMT+01:00 Pavol Rusnak <stick at gk2.sk>:

> On 03/02/15 01:05, Andreas Schildbach wrote:
> > I don't think that parameterizing will work, we can't predict future
> > BIPs. It's the same as for BIP43, in the end we agreed on just putting
> > the BIP number.
>
> Hm, let me put the questions the other way around:
>
> What gap limit should a wallet use if it encounters h=bip32?
>
> What h value should I use for myTREZOR wallets? Which is essentially a
> BIP44 wallet that produces h=bip32 xpubs with gap limit 20 ...
>
> --
> Best Regards / S pozdravom,
>
> Pavol Rusnak <stick at gk2.sk>
>
>
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