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Date: Mon, 28 Sep 2015 19:14:15 +0200
Message-ID: <CA+w+GKRcUYsKzG8n5ut-ObD1MM9bs0OD-jdHe1+cLkcO6B7wKg@mail.gmail.com>
From: Mike Hearn <hearn@vinumeris.com>
To: jl2012@xbt.hk
Content-Type: multipart/alternative; boundary=001a113fb1e4b84bd20520d1d37e
Cc: Bitcoin Dev <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Let's deploy BIP65 CHECKLOCKTIMEVERIFY!
Precedence: list

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>
> Let me try to answer this question. Softfork is beneficial to non-mining
> full nodes as they will follow the majority chain.


That is not a benefit. That is a description of what the software will do,
but not why you would want it.

In case this seems like a pedantic point, consider the consequences of
following a chain you aren't checking properly. You get SPV level security
and might calculate a corrupted ledger.

In the case of P2SH, I could make a transaction that spends someone elses
money to myself. In the case of CLTV, I could ignore the locktime
requirement.

Now yes, eventually, the miner majority will correct and uncorrupt your
ledger for you. But by then it might be too late, you may have already
acted upon the incorrect data by e.g. selling me lots of stuff that I paid
for with somebody else's coins. If you don't care about that risk, hey,
switch to an SPV wallet and save yourself a lot of disk space.


> In a hardfork, however, there is no mechanism to stop the old fork and we
> may have 2 chains co-exist for a long time.
>

There isn't any difference in how long the divergent state exists for. That
depends only on how fast people upgrade, which is unaffected by the rollout
strategy used.

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<div dir=3D"ltr"><div class=3D"gmail_extra"><div class=3D"gmail_quote"><blo=
ckquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left=
-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;paddi=
ng-left:1ex">Let me try to answer this question. Softfork is beneficial to =
non-mining full nodes as they will follow the majority chain. </blockquote>=
<div><br></div><div>That is not a benefit. That is a description of what th=
e software will do, but not why you would want it.</div><div><br></div><div=
>In case this seems like a pedantic point, consider the consequences of fol=
lowing a chain you aren&#39;t checking properly. You get SPV level security=
 and might calculate a corrupted ledger.=C2=A0</div><div><br></div><div>In =
the case of P2SH, I could make a transaction that spends someone elses mone=
y to myself. In the case of CLTV, I could ignore the locktime requirement.<=
/div><div><br></div><div>Now yes, eventually, the miner majority will corre=
ct and uncorrupt your ledger for you. But by then it might be too late, you=
 may have already acted upon the incorrect data by e.g. selling me lots of =
stuff that I paid for with somebody else&#39;s coins. If you don&#39;t care=
 about that risk, hey, switch to an SPV wallet and save yourself a lot of d=
isk space.</div><div>=C2=A0</div><blockquote class=3D"gmail_quote" style=3D=
"margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,2=
04,204);border-left-style:solid;padding-left:1ex">In a hardfork, however, t=
here is no mechanism to stop the old fork and we may have 2 chains co-exist=
 for a long time.<br></blockquote><div><br></div><div>There isn&#39;t any d=
ifference in how long the divergent state exists for. That depends only on =
how fast people upgrade, which is unaffected by the rollout strategy used.<=
/div></div></div></div>

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