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From: Tom Harding <tomh@thinlink.com>
To: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] deterministic transaction expiration
Date: Fri, 08 Aug 2014 10:38:08 -0700	[thread overview]
Message-ID: <53E50B00.8030505@thinlink.com> (raw)
In-Reply-To: <CALxbBHXh-Fktsr96PMXdohJdgcUKoNreJ-ZuApKOX3-qSkdk2w@mail.gmail.com>

Having explored more drastic approaches, it looks like Kaz' basic idea 
stands well.  His #1...

> 1. start setting nLockTime to the current height by default in newly
> created transactions (or slightly below the current height, for
> reorg-friendliness)

is already implemented in bitcoin-qt #2340, and a "final call" on 
merging it was already sent to this list.  After some thought I agree 
with its policy of eventually setting nLockTime at current-height + 1 by 
default.  This is the "best reasonably expected height" of any tx 
created right now.  It discourages fee-sniping, and if a reorg happens 
anyway, it won't actually delay inclusion of tx beyond the reasonable 
expectation sans reorg.

However right now, #2340 takes a very cautious approach and sets to 
current-height - 10 by default, with randomness to mitigate worries 
about loss of privacy.

Kaz' #2, #3 and #4 are future actions.  #4 only goes most of the way ...

> 4. add a new IsStandard rule rejecting transactions with an nLockTime
> more than N blocks behind the current tip (for some fixed value N, to
> be determined)

... a janitor mechanism is desirable to purge mempool of txes more than 
N behind current-height.

Nodes dropping a tx N blocks after they became eligible to be mined (the 
meaning of nLockTime) makes sense.  It is not an overloading or new use 
for nLockTime, but a logical extension of it.  As Kaz pointed out, this 
solves a big problem with expiring by locally measured age: 
unintentional resurrection.




  parent reply	other threads:[~2014-08-08 18:07 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-08-01  0:58 [Bitcoin-development] deterministic transaction expiration Kaz Wesley
2014-08-01  1:06 ` Peter Todd
2014-08-01  1:37   ` Kaz Wesley
2014-08-01  1:38 ` Matt Whitlock
2014-08-01  2:28   ` Gregory Maxwell
2014-08-01  3:26     ` Matt Whitlock
2014-08-01  3:31       ` Gregory Maxwell
2014-08-05 18:01         ` Alex Mizrahi
2014-08-02  0:36 ` Tom Harding
2014-08-05 17:02   ` Flavien Charlon
2014-08-05 17:48 ` Jeff Garzik
2014-08-05 18:54   ` Mike Hearn
2014-08-05 19:08     ` Jeff Garzik
2014-08-05 19:10   ` Kaz Wesley
2014-08-05 19:36     ` Jeff Garzik
2014-08-06  4:01     ` Tom Harding
2014-08-06 12:55       ` Jeff Garzik
2014-08-06 13:54         ` Mike Hearn
2014-08-06 14:44           ` Tom Harding
2014-08-06 15:08             ` Jeff Garzik
2014-08-06 15:17               ` Christian Decker
2014-08-06 15:42                 ` Peter Todd
2014-08-06 16:15                   ` Jeff Garzik
2014-08-06 17:02                     ` Tom Harding
2014-08-06 17:21                       ` Mark Friedenbach
2014-08-06 17:34                         ` Peter Todd
2014-08-06 17:24                       ` Jeff Garzik
2014-08-06 16:31                   ` Mark Friedenbach
2014-08-06 17:20                     ` Peter Todd
2014-08-06 17:30                       ` Mark Friedenbach
2014-08-06 17:38                         ` Peter Todd
2014-08-08 17:38                 ` Tom Harding [this message]
2014-08-08 18:13                   ` Jeff Garzik
2014-08-08 18:42                     ` Kaz Wesley

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