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Date: Wed, 10 Apr 2013 13:52:17 +1000
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From: Robert Backhaus <robbak@robbak.com>
To: Bitcoin Development <bitcoin-development@lists.sourceforge.net>
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Subject: Re: [Bitcoin-development]
	=?windows-1252?q?To_prevent_arbitrary_data_?=
	=?windows-1252?q?storage_in_txouts_=97_The_Ultimate_Solution?=
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That sounds workable. I take it that the P2SH address is not stored? I like
it that this denies the possibility of storing data in the block chain, but
does not block interesting uses like creating date stamps - You can still
store the 'fake P2SH' value whose checksum is secured by the blockchain.


On 10 April 2013 12:53, Gregory Maxwell <gmaxwell@gmail.com> wrote:

> (1) Define a new address type, P2SH^2 like P2SH but is instead
> H(H(ScriptPubKey)) instead of H(ScriptPubKey). A P2SH^2 address it is
> a hash of a P2SH address.
>
> (2) Make a relay rule so that to relay a P2SH^2  you must include
> along the inner P2SH address.  All nodes can trivially verify it by
> hashing it.
>
> (2a) If we find that miners mine P2SH^2 addresses where the P2SH
> wasn't relayed (e.g. they want the fees) we introduce a block
> discouragement rule where a block is discouraged if you receive it
> without receiving the P2SH^2 pre-images for it.
>
> With this minor change there is _no_ non-prunable location for users
> to cram data into except values.  (and the inefficiency of cramming
> data into values is a strong deterrent in any case)
>
> The same thing could also be done for OP_RETURN PUSH value outputs
> used to link transactions to data. Make the data be a hash, outside of
> the txn include the preimage of the hash.
>
>
> ------------------------------------------------------------------------------
> Precog is a next-generation analytics platform capable of advanced
> analytics on semi-structured data. The platform includes APIs for building
> apps and a phenomenal toolset for data science. Developers can use
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<div dir=3D"ltr"><span style=3D"font-family:arial,sans-serif;font-size:13px=
">That sounds workable. I take it that the P2SH address is not stored? I li=
ke it that this denies the possibility of storing data in the block chain, =
but does not block interesting uses like creating date stamps - You can sti=
ll store the &#39;fake P2SH&#39; value whose checksum is secured by the blo=
ckchain.</span><br>
</div><div class=3D"gmail_extra"><br><br><div class=3D"gmail_quote">On 10 A=
pril 2013 12:53, Gregory Maxwell <span dir=3D"ltr">&lt;<a href=3D"mailto:gm=
axwell@gmail.com" target=3D"_blank">gmaxwell@gmail.com</a>&gt;</span> wrote=
:<br><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-le=
ft:1px #ccc solid;padding-left:1ex">
(1) Define a new address type, P2SH^2 like P2SH but is instead<br>
H(H(ScriptPubKey)) instead of H(ScriptPubKey). A P2SH^2 address it is<br>
a hash of a P2SH address.<br>
<br>
(2) Make a relay rule so that to relay a P2SH^2 =A0you must include<br>
along the inner P2SH address. =A0All nodes can trivially verify it by<br>
hashing it.<br>
<br>
(2a) If we find that miners mine P2SH^2 addresses where the P2SH<br>
wasn&#39;t relayed (e.g. they want the fees) we introduce a block<br>
discouragement rule where a block is discouraged if you receive it<br>
without receiving the P2SH^2 pre-images for it.<br>
<br>
With this minor change there is _no_ non-prunable location for users<br>
to cram data into except values. =A0(and the inefficiency of cramming<br>
data into values is a strong deterrent in any case)<br>
<br>
The same thing could also be done for OP_RETURN PUSH value outputs<br>
used to link transactions to data. Make the data be a hash, outside of<br>
the txn include the preimage of the hash.<br>
<br>
---------------------------------------------------------------------------=
---<br>
Precog is a next-generation analytics platform capable of advanced<br>
analytics on semi-structured data. The platform includes APIs for building<=
br>
apps and a phenomenal toolset for data science. Developers can use<br>
our toolset for easy data analysis &amp; visualization. Get a free account!=
<br>
<a href=3D"http://www2.precog.com/precogplatform/slashdotnewsletter" target=
=3D"_blank">http://www2.precog.com/precogplatform/slashdotnewsletter</a><br=
>
_______________________________________________<br>
Bitcoin-development mailing list<br>
<a href=3D"mailto:Bitcoin-development@lists.sourceforge.net">Bitcoin-develo=
pment@lists.sourceforge.net</a><br>
<a href=3D"https://lists.sourceforge.net/lists/listinfo/bitcoin-development=
" target=3D"_blank">https://lists.sourceforge.net/lists/listinfo/bitcoin-de=
velopment</a><br>
</blockquote></div><br></div>

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