MIME-Version: 1.0
Date: Wed, 28 Oct 2015 10:06:22 -0400
Message-ID: <CABsx9T0Evf3B_NtmdKxc_M1xRQh-jSC4JzTHCx8Ez9RzCypvMg@mail.gmail.com>
From: Gavin Andresen <gavinandresen@gmail.com>
To: Bitcoin Dev <bitcoin-dev@lists.linuxfoundation.org>
Content-Type: multipart/alternative; boundary=001a113eaaa4ffd24505232ab290
Subject: [bitcoin-dev] Compatibility requirements for hard or soft forks
Precedence: list

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I'm hoping this fits under the moderation rule of "short-term changes to
the Bitcoin protcol" (I'm not exactly clear on what is meant by
"short-term"; it would be lovely if the moderators would start a thread on
bitcoin-discuss to clarify that):


Should it be a requirement that ANY one-megabyte transaction that is valid
under the existing rules also be valid under new rules?

Pro:  There could be expensive-to-validate transactions created and given a
lockTime in the future stored somewhere safe. Their owners may have no
other way of spending the funds (they might have thrown away the private
keys), and changing validation rules to be more strict so that those
transactions are invalid would be an unacceptable confiscation of funds.

Con: It is extremely unlikely there are any such large, timelocked
transactions, because the Core code has had a clear policy for years that
100,000-byte transactions are &quot;standard&quot; and are relayed and
mined, and
larger transactions are not. The requirement should be relaxed so that only
valid 100,000-byte transaction under old consensus rules must be valid
under new consensus rules (larger transactions may or may not be valid).


I had to wrestle with that question when I implemented BIP101/Bitcoin XT
when deciding on a limit for signature hashing (and decided the right
answer was to support any "non-attack"1MB transaction; see
https://bitcoincore.org/~gavin/ValidationSanity.pdf for more details).

-- 
--
Gavin Andresen

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<div dir=3D"ltr">I&#39;m hoping this fits under the moderation rule of &quo=
t;short-term changes to the Bitcoin protcol&quot; (I&#39;m not exactly clea=
r on what is meant by &quot;short-term&quot;; it would be lovely if the mod=
erators would start a thread on bitcoin-discuss to clarify that):<div><br><=
br>Should it be a requirement that ANY one-megabyte transaction that is val=
id<br>under the existing rules also be valid under new rules?<br><br>Pro: =
=C2=A0There could be expensive-to-validate transactions created and given a=
<br>lockTime in the future stored somewhere safe. Their owners may have no<=
br>other way of spending the funds (they might have thrown away the private=
<br>keys), and changing validation rules to be more strict so that those<br=
>transactions are invalid would be an unacceptable confiscation of funds.<b=
r><br>Con: It is extremely unlikely there are any such large, timelocked<br=
>transactions, because the Core code has had a clear policy for years that<=
br>100,000-byte transactions are &amp;quot;standard&amp;quot; and are relay=
ed and mined, and<br>larger transactions are not. The requirement should be=
 relaxed so that only<br>valid 100,000-byte transaction under old consensus=
 rules must be valid<br>under new consensus rules (larger transactions may =
or may not be valid).<br><br><br>I had to wrestle with that question when I=
 implemented BIP101/Bitcoin XT<br>when deciding on a limit for signature ha=
shing (and decided the right<br>answer was to support any &quot;non-attack&=
quot;1MB transaction; see<br><a href=3D"https://bitcoincore.org/~gavin/Vali=
dationSanity.pdf">https://bitcoincore.org/~gavin/ValidationSanity.pdf</a> f=
or more details).<br><br>-- <br><div class=3D"gmail_signature">--<br>Gavin =
Andresen<br></div>
</div></div>

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