Received-SPF: pass (sog-mx-4.v43.ch3.sourceforge.com: domain of gmail.com
	designates 209.85.210.180 as permitted sender)
	client-ip=209.85.210.180; envelope-from=watsonbladd@gmail.com;
	helo=mail-ia0-f180.google.com; 
MIME-Version: 1.0
Sender: watsonbladd@gmail.com
In-Reply-To: <CAAS2fgQxQEAtspRQixU7KAqhcXYnev=20-hbDpMCO9nTEKT+RQ@mail.gmail.com>
References: <CAErK2CgWFarfs1WhGHs2L0b6ZuqCMhu72+dLNj0EZ1vN8=Au=g@mail.gmail.com>
	<CAAS2fgQxQEAtspRQixU7KAqhcXYnev=20-hbDpMCO9nTEKT+RQ@mail.gmail.com>
Date: Tue, 4 Dec 2012 21:36:29 -0600
Message-ID: <CACsn0cnwyWL2NL9eEboxqgTS-h5MS+LHajKOYpFiCXCBs6pLug@mail.gmail.com>
From: Watson Ladd <wbl@uchicago.edu>
To: Gregory Maxwell <gmaxwell@gmail.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable
Cc: "bitcoin-development@lists.sourceforge.net"
	<bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] String-based Hierarchical Deterministic
 Keys - Alternative to BIP 32
Precedence: list

On Tue, Dec 4, 2012 at 9:23 PM, Gregory Maxwell <gmaxwell@gmail.com> wrote:
> On Tue, Dec 4, 2012 at 10:06 PM, Mike Koss <mike@coinlab.com> wrote:
>> I've implemented an alternative to the BIP 32 proposal.  I wanted a syst=
em
>> based on a hierarchical string representation (rather than hierarchy of
>> integers as BIP 32 proposes).  For example I name keys like this:
>>
>> [hd1.75491111].store.1. 1D7GM5dkUtxvGeWgn7SYtanBuyj1MD1EZy
>> [hd1.75491111].store.2. 1QAqDbzpNKViGSjVe1XmnGbmZtvz5hM7t1
>> [hd1.75491111].store.3. 14XkSN92QLGeorYPpoVbG87DQhowEx3mFn
>> [hd1.75491111].store.4. 1JLcGdod6Wm33rMZuZZUmAEE6osLhM4QMn
>>
>> First draft of proposal:
>>
>> https://gist.github.com/4211704
>
> As Pieter pointed out recently=E2=80=94 it's not (realistically) possible=
 to
> blindly iterate through strings.  This means your proposal loses the
> backup recoverablity property which is part the point of a
> deterministic wallet:  If you have a backup prior to a new string name
> being established you must also have a reliable backup of the string
> as well.

I would like to note that BIP32 and this new proposal have a missing
feature: being able to spend
a coin sent to an address generated by this scheme implies being able
to spend any coin generated
by this scheme.

The easiest deterministic wallet construction is simply to use a
stream cipher to generate random
bytes used as the private keys in a wallet. Hierarchical constructions
do not seem to me to add more,
other then distinguishing transactions by sending to unique addresses,
which could be done by other means.

>
> Of course, if you're backing up the strings then you can also backup a
> map equating the hdwallet indexes to your strings, and in the event of
> a catastrophic loss where you are only left with the original ultimate
> root you lose no coins (only metadata) with the BIP32 scheme. If,
> instead, we have your scheme and the backup of strings is incomplete
> then some or all assigned coin may be lost forever.
>
> Your extended hierarchy of multiplers also makes me uncomfortable.
> BIP32 uses a HMAC in its construction to obtain strongly unstructured
> points.

I read BIP32. And while the multipliers at each level are
unstructured, the ones in the next level are products
of the ones before i.e. we have a multiplication tree with random
looking branches.
Note that the order of the basepoint is prime or a small cofactor
times a prime, so this isn't an issue (usually:
the cofactor could be annoying).

--
"Those who would give up Essential Liberty to purchase a little
Temporary Safety deserve neither  Liberty nor Safety."
-- Benjamin Franklin