Re: [bitcoin-dev] BIP: Block signal enforcement via tx fees

[Rusty Russell <rusty@rustcorp.com.au>]

Russell O'Connor via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org>
writes:
> On Sat, May 13, 2017 at 1:26 AM, Luke Dashjr <luke@dashjr.org> wrote:
>
>> Versionbits change/lose their meaning after the deployment timeout. For
>> this
>> reason, the timeout must be specified so the check is skipped when that
>> occurs.
>>
>
> To add a timeout a user can optionally bundle a pair of similar
> transactions.  One with the transaction version bits set and a second with
> a locktime set.  The effect is the same.

I have a similar proposal to Russell; use tx nVersion.  However, my
subset is simpler, and uses fewer precious nVersion bits:

1. Top version 26 bits must be 1 (say)
2. Next bit indicates positive (must have bit set) or negative (must NOT
   have bit set).
3. Bottom 5 bits refer to which BIP8/9 bit we're talking about.

This only allows specifying a single bit, and only support BIP8/9-style
signalling.

I believe we can skip the timeout: miners don't signal 100% either way
anyway.  If a BIP is in LOCKIN, wallets shouldn't set positive on that
bit (this gives them two weeks).  Similarly, if a BIP is close to
FAILED, don't set positive on your tx.  Wallets shouldn't signal until
any bit until see some minimal chance it's accepted (eg. 1 in 20 blocks).

> I recall chatting about this idea recently and my conclusion was the same
> as Peter Todd's conclusion: this will just encourage miners to false signal
> readiness with undermines both BIP 9 and BIP 8.

This is gentler on miners than a UASF flag day, and does offer some
harder-to-game signalling from bitcoin users.

False signalling miners still have the 2 week LOCKIN period to upgrade,
otherwise they can already lose money.  You could argue they're *more*
likely to upgrade with a signal that significant parts of the economy
have done so.

Cheers,
Rusty.