[Bitcoin-development] Consensus-enforced transaction replacement via sequence numbers

Mark Friedenbach mark at friedenbach.org
Thu May 28 15:38:43 UTC 2015


Oh ok you mean a semantic difference for the purpose of explaining. It
doesn't actually change the code.

Regarding saving more bits, there really isn't much room if you consider
time-based relative locktimes and long-lived channels on the order of a
year or more.

On Thu, May 28, 2015 at 8:18 AM, Tier Nolan <tier.nolan at gmail.com> wrote:

> On Thu, May 28, 2015 at 3:59 PM, Mark Friedenbach <mark at friedenbach.org>
> wrote:
>
>> Why 3? Do we have a version 2?
>>
> I meant whatever the next version is, so you are right, it's version 2.
>
>> As for doing it in serialization, that would alter the txid making it a
>> hard fork change.
>>
> The change is backwards compatible (since there is no restrictions on
> sequence numbers).   This makes it a soft fork.
>
> That doesn't change the fact that you are changing what a field in the
> transaction represents.
>
> You could say that the sequence number is no longer encoded in the
> serialization, it is assumed to be 0xFFFFFFFF for all version 2+
> transactions and the relative locktime is a whole new field that is the
> same size (and position).
>
> I think keeping some of the bytes for other uses is a good idea.  The
> entire top 2 bytes could be ignored when working out relative locktime
> verify.  That leaves them fully free to be set to anything.
>
> It could be that if the MSB of the bottom 2 bytes is set, then that
> activates the rule and the top 2 bytes are ignored.
>
> Are there any use-cases which need a RLTV of more than 8191 blocks delay
> (that can't be covered by the absolute version)?
>
>
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