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From: Gregory Maxwell <gmaxwell@gmail.com>
To: Matt Whitlock <bip@mattwhitlock.name>
Cc: Bitcoin Development <bitcoin-development@lists.sourceforge.net>,
	Flavien Charlon <flavien.charlon@coinprism.com>
Subject: Re: [Bitcoin-development] [BIP draft] CHECKLOCKTIMEVERIFY - Prevent a txout from being spent until an expiration time
Date: Fri, 3 Oct 2014 09:17:48 -0700	[thread overview]
Message-ID: <CAAS2fgT5VSQywp_5_N2JboVT-LQDZ76UQXBvwZ4KfdQ06jAPig@mail.gmail.com> (raw)
In-Reply-To: <1987325.zKPNeYyO8K@crushinator>

On Fri, Oct 3, 2014 at 7:28 AM, Matt Whitlock <bip@mattwhitlock.name> wrote:
> Is there a reason why we can't have the new opcode simply replace the top stack item with the block height of the txout being redeemed?

This would not be soft-forking compatible.

It also would be unsafe in that it would result in transactions which
once mined could not be restored in a reorg through no fault of the
participants, which makes the coins less fungible and differently safe
to accept. It risks creating weird pressures around immediate block
admission since a one additional block delay could forever censor such
a transaction (E.g. increases the power of single miners to censor or
steal). Avoiding this is a conscious decision in Bitcoin and also part
of the justification for the 100 block maturity of newly generated
coins.

It also would require violating the script/transaction/block layering
more substantially, complicating implementations, and making the
validity of a script no longer a deterministic pure function of the
transaction.

Avoiding these issues is a conscious design in OP_CHECKLOCKTIMEVERIFY.
I would strenuously oppose a proposal which failed in any of these
respects.

> Then arbitrary logic could be implemented, including "output cannot be spent until a certain time" and also "output can ONLY be spent until a certain time," as well as complex logic with alternative key groups with differing time constraints.

You can already achieve the not spendable after logic with a
cancellation spend that moves the coin in the usual way. (Which
doesn't even require the participant be online, with the help of some
network service to queue unlocked transactions).

> OP_CHECKLOCKTIMEVERIFY, as conceived, seems too limited, IMHO.

It is intentionally so, and yet it covers the intended use cases;
including ones with alternative key groups, they are just not
exclusive.



  parent reply	other threads:[~2014-10-03 16:17 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-10-01 13:08 [Bitcoin-development] [BIP draft] CHECKLOCKTIMEVERIFY - Prevent a txout from being spent until an expiration time Peter Todd
2014-10-01 15:01 ` Gavin Andresen
2014-10-02  1:06   ` Peter Todd
2014-10-01 15:29 ` Sergio Lerner
2014-10-01 17:06   ` Peter Todd
2014-10-01 18:23 ` Luke Dashjr
2014-10-01 20:58   ` Gavin Andresen
2014-10-01 21:04     ` Alan Reiner
2014-10-01 21:34       ` Gavin Andresen
2014-10-02  0:12         ` Peter Todd
2014-10-02  0:05   ` Peter Todd
2014-10-02  0:55     ` Luke Dashjr
2014-10-02  1:09       ` Peter Todd
2014-10-02 15:05         ` Flavien Charlon
2014-10-03 14:28           ` Matt Whitlock
2014-10-03 14:30             ` Matt Whitlock
2014-10-03 16:17             ` Gregory Maxwell [this message]
2014-10-03 17:50             ` Luke Dashjr
2014-10-03 20:58               ` Mike Hearn
2014-10-03 23:12                 ` Jeff Garzik
2014-10-04  0:38                   ` Peter Todd
2014-10-04 12:58                     ` Mike Hearn
2014-10-07 15:50                       ` Gavin Andresen
2014-10-07 16:08                         ` Mike Hearn
2014-10-08 10:26                           ` Wladimir
2014-10-09  3:13                             ` Alan Reiner
2014-10-09  6:14                               ` Adam Back
2014-10-09  6:28                                 ` Gregory Maxwell
2014-10-09  6:33                                   ` Peter Todd
2014-10-09  6:40                                     ` Gregory Maxwell
2014-10-08  4:07                         ` Tom Harding
2014-10-08 10:15                           ` Mike Hearn
2015-03-16 22:22 ` [Bitcoin-development] Relative CHECKLOCKTIMEVERIFY (was CLTV proposal) Matt Corallo
2015-03-19 17:39   ` Zooko Wilcox-OHearn
2015-04-21  7:59   ` Peter Todd
2015-04-26 11:35     ` Jorge Timón
2015-04-26 12:20       ` Jorge Timón
2015-04-27 19:35         ` Peter Todd
2015-04-28  7:44           ` Jorge Timón
2015-05-04  2:15     ` Matt Corallo
2015-05-04 11:24       ` Jorge Timón
2015-05-05  0:41         ` Btc Drak
2015-05-05 19:19           ` Jorge Timón
2015-05-05 20:38         ` Tier Nolan
2015-05-06  7:37           ` Jorge Timón
2015-05-06 22:09             ` Tier Nolan

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