[Bitcoin-development] Version bytes

[John Smith]

I agree. I think breaking compatiblity with older address (even testnet) is
not a

On Fri, Jul 8, 2011 at 6:36 AM, Stefan Thomas <moon at justmoon.de> wrote:

> Hey Pieter,
>
> > Otherwise, we could reset testnet (not actually reset, just
> > change its addresses a bit), and simply state odd=testnet, even=realnet.
>
> We could use the XOR hack for now and remove it the next time we reset
> testnet. But I do think the 111 is baggage we want to get rid of. Using
> the lsb as a simple flag is much cleaner.
>
> Cheers,
>
> Stefan
>
>
> On 7/7/2011 1:15 PM, Pieter Wuille wrote:
> > Hello everyone,
> >
> > after a discussion on IRC, we decided to try to standardize the version
> bytes
> > used by bitcoin for several applications.
> >
> > There are 3 components that seem meaningful:
> > * network? (realnet, testnet, alternate chains?)
> > * data class? (address, private key, master key, ...?)
> > * version? (real version, per data class defined)
> >
> > There is no technical reason why different network and different data
> classes
> > would need separate version bytes, but i think it is a good thing to keep
> > them from colliding. People will mix them up, and when things are well
> > defined, a nice warning message could help a lot ("Oops it seems you
> entered
> > a private key instead of an address!").
> >
> > So, first of all, there is already one actually used alternate chain,
> namely
> > namecoin, using version byte 52 for addresses. For this reason, i'd like
> to
> > reserve bit 16 in the version byte for "alternate chain". When bit 16 is
> set,
> > everything is up to the network itself, and no further semantics are
> defined.
> >
> > When bit 16 isn't set:
> >
> > Then remains the rest of the network. The problem is that testnet already
> uses
> > version 111, which is not a single bit. We can use a trick though, namely
> > choosing bit 1 for testnet, and if bit 1 is set, XOR the rest of the
> version
> > number with 111. Otherwise, we could reset testnet (not actually reset,
> just
> > change its addresses a bit), and simply state odd=testnet, even=realnet.
> >
> > That leaves use with 6 more bits to play with, namely 128,64,32 and
> 8,4,2.
> > As 128 is already used for private keys, let's use (128,64,32) for data
> classes,
> > and (8,4,2) for versions.
> >
> > So, in full:
> > * Bits 128/64/32 define data class
> > ** 0 = address
> > ** 32,64,96,160,192 = reserved for future use
> > ** 128 = private key
> > ** 224 = extended data class, another "data class" byte follows
> > * Bit 16 defines "private"
> > ** 0 = bitcoin
> > ** 16 = alternate chain
> > * Bits 8/4/2 define version number
> > ** 0 = only thing used for now
> > ** 2,4,6,8,10,12 = reserved for future use
> > ** 14 = extended version, another version byte follows
> > * Bit 1 defines testnet
> > ** 0 = realnet
> > ** 1 = testnet (possibly using XOR 111, if not reset)
> >
> > This whole discussion started when Stefan wanted to define a format for
> master keys from which
> > to derive deterministic wallet keys, i suggest using data class 192 for
> that, leaving the
> > lower numbers for more basic data, like public keys.
> >
> > Any comments?
> >
>
>
>
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