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Date: Thu, 27 Mar 2014 17:14:05 +0100
Message-ID: <CAPg+sBjwf1TcK1CGKVKFzYbV-78j8t-pav7=PEgG7Yqi6-yE7A@mail.gmail.com>
From: Pieter Wuille <pieter.wuille@gmail.com>
To: Allen Piscitello <allen.piscitello@gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
Cc: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] New BIP32 structure
Precedence: list

Just chiming in...

I'm not opposed to a more generic default key tree, but we need to
standardize this soon I believe. There are already existing code bases
that implement BIP32 wallets (and more are popping up...); just using
a separate one will result in lots of incompibilities.

That said, I'm not convinced about the extra layers. The "cointype" in
my opinion isn't necessary inside the derivation. There is already
support (4 bytes!) for magic bytes in the serialized form. Inside
applications/p2p it should always be known to which chain it applies,
and outside of that you shouldn't transfer raw keys. Maybe seeds need
some marker, but that's a separate case anyway. Mainnet and testnet
have specified magics here already - alts can define what they want
imho.

A 'reserved' field for future extensions may be useful, but as already
suggested by Mike, I don't believe we can encode how key chains are to
be used inside the derivation structure anyway. The most basic case
(not losing money in a wallet without special structure) can perhaps
be supported with just "the blockchain is your wallet", but I don't
believe this principle can scale to more advanced uses anyway, and you
need metadata in the wallet to deal with it.

In my view, your wallet just has a bunch of chains, and each chain
gets used for a particular purpose, fixing how the derivation beneath
it works. Either that is as a wallet, as part of a pair of multisig
keys, as a recurring payment receiver, ... or more complex things.
Some of these will require extra layers beneath, but that is
application specific. You would import a chain into your (advanced)
wallet with a particular extpub/extpriv code, and some metadata on how
to use it. Serialization formats for such designated extra uses sounds
better to me than trying to fit it into the derivation structure.

-- 
Pieter


On Thu, Mar 27, 2014 at 4:57 PM, Allen Piscitello
<allen.piscitello@gmail.com> wrote:
> Don't most of these coins have a magic number already assigned that is
> unique? (0xD9B4BEF9 for Bitcoin, 0x0709110B for Testnet, FBC0XB6DB for
> Litecoin, etc...).  This seems like a good candidate for identifying coins,
> and also supports Testnet cases well.  Maybe there are some alts without
> such a magic number that might prevent that?
>
> -Allen
>
>
> On Thu, Mar 27, 2014 at 10:43 AM, Jeff Garzik <jgarzik@bitpay.com> wrote:
>>
>> On Thu, Mar 27, 2014 at 3:09 AM, Tamas Blummer <tamas@bitsofproof.com>
>> wrote:
>> > A notable suggestion was to instead of building a directory of magic
>> > numbers
>> > (like 0 for Bitcoin, 1 for Litecoin etc) use a hash of the word
>> > "Bitcoin",
>> > "Litecoin", "Dogecoin", so collosion is unlikely and
>> > cetral directory is not needed.
>>
>> +1 good idea
>>
>> --
>> Jeff Garzik
>> Bitcoin core developer and open source evangelist
>> BitPay, Inc.      https://bitpay.com/
>>
>>
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