Thanks for the proposal.

Three points it could see as possible improvements:

1.
From what I know, the exact birthday in seconds doesn’t matter that much therefore it may be possible to just use 13 or 16bits to create a representation in week from 2009-01-09 00:00 UTC. 13bits would give you 157 years.
Always round down to the beginning of the week when the key was created.
But not sure if it’s worth to save ~two bytes for that.
Also not sure if the key-birthday in seconds could have a security or privacy implication (week maybe better).

2.
Would it make sense to have special depth bytes that directly implies it’s a BIP44 master key (and therefore avoid the bip32 path serialisation)? I know some „centralised“ table need to be available for that which may be not a good idea. But maybe the BIP could reserve a couple of depth-bytes (maybe 0xF0 to 0xFF) for predefined paths.

3.
Would adding a version bit make sense to allow future extensions?


/jonas


> Am 06.09.2017 um 15:29 schrieb Pavol Rusnak via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org>:
> 
> The discussion about changing bip32 version bytes for SegWit got me
> thinking and I ended up with what I think is the best proposal:
> 
> https://github.com/satoshilabs/slips/blob/master/slip-0032.md
> 
> (It is hosted in SL repo for now, but if there is will, I would love to
> have this added to BIP repo as an extension to BIP32)
> 
> Feel free to comment.
> 
> --
> Best Regards / S pozdravom,
> 
> Pavol "stick" Rusnak
> CTO, SatoshiLabs
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