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Date: Sun, 20 Dec 2015 06:34:29 -0500
Message-ID: <CADm_Wca0cWRvcVaJ+p47A49yffQ1vP=u4807j7axn=mdBdsUGQ@mail.gmail.com>
From: Jeff Garzik <jgarzik@gmail.com>
To: Peter Todd <pete@petertodd.org>
Content-Type: multipart/alternative; boundary=089e011763436bb233052752c15c
Cc: Bitcoin Dev <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Forget dormant UTXOs without confiscating bitcoin
Precedence: list

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On Sun, Dec 20, 2015 at 6:24 AM, Peter Todd via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> What I proprosed is that a consensus-critical maximum UTXO age be part
> of the protocol; UTXO's younger than that age are expected to be cached.
> For UTXO's older than that age, they can be dropped from the cache,
> however to spend them you are required to provide the proof, and that
> proof counts as blockchain space to account for the fact that they do
> need to be broadcast on the network.


Yes, this is almost what -has- to happen in the long term.

Ideally we should start having wallets generate those proofs now, and then
introduce the max-age as a second step as a planned hard fork a couple
years down the line.

However,
1) There is also the open question of "grandfathered" UTXOs - for those
wallets generated in 2009, buried in a landfill and then dug out 10 years
ago

2) This reverses the useful minimization attribute of HD wallets - "just
backup the seed"

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<div dir=3D"ltr">On Sun, Dec 20, 2015 at 6:24 AM, Peter Todd via bitcoin-de=
v <span dir=3D"ltr">&lt;<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation=
.org" target=3D"_blank">bitcoin-dev@lists.linuxfoundation.org</a>&gt;</span=
> wrote:<br><div class=3D"gmail_extra"><div class=3D"gmail_quote"><blockquo=
te class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc so=
lid;padding-left:1ex">What I proprosed is that a consensus-critical maximum=
 UTXO age be part<br>
of the protocol; UTXO&#39;s younger than that age are expected to be cached=
.<br>
For UTXO&#39;s older than that age, they can be dropped from the cache,<br>
however to spend them you are required to provide the proof, and that<br>
proof counts as blockchain space to account for the fact that they do<br>
need to be broadcast on the network.</blockquote><div></div></div><br></div=
><div class=3D"gmail_extra">Yes, this is almost what -has- to happen in the=
 long term.</div><div class=3D"gmail_extra"><br></div><div class=3D"gmail_e=
xtra">Ideally we should start having wallets generate those proofs now, and=
 then introduce the max-age as a second step as a planned hard fork a coupl=
e years down the line.</div><div class=3D"gmail_extra"><br></div><div class=
=3D"gmail_extra">However,</div><div class=3D"gmail_extra">1) There is also =
the open question of &quot;grandfathered&quot; UTXOs - for those wallets ge=
nerated in 2009, buried in a landfill and then dug out 10 years ago</div><d=
iv class=3D"gmail_extra"><br></div><div class=3D"gmail_extra">2) This rever=
ses the useful minimization attribute of HD wallets - &quot;just backup the=
 seed&quot;</div><div class=3D"gmail_extra"><br></div><div class=3D"gmail_e=
xtra"><br></div></div>

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