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Date: Thu, 27 Mar 2014 13:58:19 +0000
Subject: Re: [Bitcoin-development] New BIP32 structure
Precedence: list

Good to hear the bip32 wallet structure is _so_ close to being standardised.
For MultiBit HD, we have put in support for 12/18/24 words but have the UI =
'suggest' to use 12.
You can see this on the wallet creation wizard Gary recently blogged about:
https://multibit.org/blog/2014/03/26/multibit-hd-welcome-wizard.html

There's a little combo for the seed length, with 12 as the default.


@Thomas. You mention gaps. We are creating new addresses on the UI in a pan=
el marked 'Request' where the user also types in a QR code label and a note=
 to themselves. This gets stored away as a first class 'PaymentRequest'. Th=
e UI 'suggests' that each address is used once. There will be some gaps (wh=
ere the payment request is never paid) but we aren't bulk creating addresse=
s. I am hoping this shouldn't cause Electrum a problem.

We are also storing a timestamp (the number of days since the genesis block=
) to help wallet restore but that is SPV specific.


On Thu, Mar 27, 2014, at 01:49 PM, Thomas Voegtlin wrote:
>=20
>=20
> Le 27/03/2014 13:49, Mike Hearn a =E9crit :
IP32 allows for a range of entropy sizes and it so happens that
> > they picked 256 bits instead of 128 bits.
> >
> > I'd have thought that there is a right answer for this. 2^128 should not
> > be brute forceable, and longer sizes have a cost in terms of making the
> > seeds harder to write down on paper. So should this be a degree of free=
dom?
> >
>=20
>=20
> Here is what I understand:
>=20
> 2^128 iterations is not brute forcable today, and will not be for the=20
> foreseeable future.
>=20
> An EC pubkey of length n can be forced in approximately 2^(n/2)=20
> iterations (see http://ecc-challenge.info/) Thus, Bitcoin pubkeys, which=
=20
> are 256 bits, would require 2^128 iterations. This is why unused=20
> addresses (160 bits hash) are better protected than already used ones.
>=20
> However, people tend to believe that a public key of size n requires 2^n=
=20
> iterations. This belief might have been spread by this popular image:
> https://bitcointalk.org/index.php?topic=3D508880.msg5616146#msg5616146
>=20
>=20
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--=20
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