Received-SPF: pass (sog-mx-3.v43.ch3.sourceforge.com: domain of gmail.com
	designates 209.85.213.182 as permitted sender)
	client-ip=209.85.213.182; envelope-from=gmaxwell@gmail.com;
	helo=mail-ig0-f182.google.com; 
MIME-Version: 1.0
In-Reply-To: <55146E2C.9020105@thinlink.com>
References: <55121611.1030104@thinlink.com>
	<CAAS2fgRzskGcHjEhJLnyu-VMTR49i-Wo9TbOOqkHqEasxuO71A@mail.gmail.com>
	<551301F0.9020806@thinlink.com>
	<CAAS2fgQMW+Htqu0wonL7r-ZN_t0evRayDCGRMKYzRUaCm6wxjw@mail.gmail.com>
	<55146E2C.9020105@thinlink.com>
Date: Thu, 26 Mar 2015 20:42:55 +0000
Message-ID: <CAAS2fgSSOQi4uL95S=GUdXGKZK_y4aNTUoOqkkaLFvzAVPnRig@mail.gmail.com>
From: Gregory Maxwell <gmaxwell@gmail.com>
To: Tom Harding <tomh@thinlink.com>
Content-Type: text/plain; charset=UTF-8
Cc: Bitcoin Development <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] Address Expiration to Prevent Reuse
Precedence: list

On Thu, Mar 26, 2015 at 8:38 PM, Tom Harding <tomh@thinlink.com> wrote:
> I addressed that by limiting the duplicate check to an X-block segment.  X
> is hard-coded in this simple scheme (X=144  => "1-day addresses").  You
> could picture a selectable expiration duration too.

If its to be heuristic in any case why not make it a client feature
instead of a consensus rule?

If someone wants to bypass anything they always can, thats what I mean
by "hide their payment under a rock"

E.g. I can take your pubkey, add G to it (adding 1 to the private
key), strip off the time limits, and send the funds.

"What do you mean I didn't pay you? I wrote a check. locked it in a
safe, and burred it in your back garden."

The answer to this can only be that payment is only tendered when its
made _exactly_ to the payee's specifications.

If someone violates the specifications all they're doing is destroying
coins. Nothing can stop people from destroying coins...

Which is why a simpler, safer, client enforced behavior is probably
preferable. Someone who wants to go hack their client to make a
payment that isn't according to the payee will have to live with the
results, esp. as we can't prevent that in a strong sense.