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From: Sergio Demian Lerner <sergio.d.lerner@gmail.com>
Date: Fri, 26 Feb 2016 20:06:40 -0300
Message-ID: <CAKzdR-rp0Bqkj3PLWHx4etHejy2C997M3fGJy702jPdVThxPZg@mail.gmail.com>
To: Gregory Maxwell <greg@xiph.org>
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Cc: Bitcoin Dev <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] The first successful Zero-Knowledge Contingent
	Payment
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Congratulations!

It a property of the SKCP system that the person who performed the trusted
setup cannot extract any information from a proof?

In other words, is it proven hard to obtain information from a proof by the
buyer?

On Fri, Feb 26, 2016 at 6:42 PM, Gregory Maxwell via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> I am happy to announce the first successful Zero-Knowledge Contingent
> Payment (ZKCP) on the Bitcoin network.
>
> ZKCP is a transaction protocol that allows a buyer to purchase
> information from a seller using Bitcoin in a manner which is private,
> scalable, secure, and which doesn=E2=80=99t require trusting anyone: the
> expected information is transferred if and only if the payment is
> made. The buyer and seller do not need to trust each other or depend
> on arbitration by a third party.
>
> Imagine a movie-style =E2=80=9Cbriefcase swap=E2=80=9D (one party with a =
briefcase
> full of cash, another containing secret documents), but without the
> potential scenario of one of the cases being filled with shredded
> newspaper and the resulting exciting chase scene.
>
> An example application would be the owners of a particular make of
> e-book reader cooperating to purchase the DRM master keys from a
> failing manufacturer, so that they could load their own documents on
> their readers after the vendor=E2=80=99s servers go offline. This type of=
 sale
> is inherently irreversible, potentially crosses multiple
> jurisdictions, and involves parties whose financial stability is
> uncertain=E2=80=93meaning that both parties either take a great deal of r=
isk
> or have to make difficult arrangement. Using a ZKCP avoids the
> significant transactional costs involved in a sale which can otherwise
> easily go wrong.
>
> In today=E2=80=99s transaction I purchased a solution to a 16x16 Sudoku p=
uzzle
> for 0.10 BTC from Sean Bowe, a member of the Zcash team, as part of a
> demonstration performed live at Financial Cryptography 2016 in
> Barbados. I played my part in the transaction remotely from
> California.
>
> The transfer involved two transactions:
>
> 8e5df5f792ac4e98cca87f10aba7947337684a5a0a7333ab897fb9c9d616ba9e
> 200554139d1e3fe6e499f6ffb0b6e01e706eb8c897293a7f6a26d25e39623fae
>
> Almost all of the engineering work behind this ZKCP implementation was
> done by Sean Bowe, with support from Pieter Wuille, myself, and Madars
> Virza.
>
>
> Read more, including technical details at
>
> https://bitcoincore.org/en/2016/02/26/zero-knowledge-contingent-payments-=
announcement/
>
> [I hope to have a ZKCP sudoku buying faucet up shortly. :) ]
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev@lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>

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<div dir=3D"ltr"><div><div><div>Congratulations!<br></div></div><br>It a pr=
operty of the SKCP system that the person who performed the trusted setup c=
annot extract any information from a proof?<br><br></div>In other words, is=
 it proven hard to obtain information from a proof by the buyer? <br></div>=
<div class=3D"gmail_extra"><br><div class=3D"gmail_quote">On Fri, Feb 26, 2=
016 at 6:42 PM, Gregory Maxwell via bitcoin-dev <span dir=3D"ltr">&lt;<a hr=
ef=3D"mailto:bitcoin-dev@lists.linuxfoundation.org" target=3D"_blank">bitco=
in-dev@lists.linuxfoundation.org</a>&gt;</span> wrote:<br><blockquote class=
=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padd=
ing-left:1ex">I am happy to announce the first successful Zero-Knowledge Co=
ntingent<br>
Payment (ZKCP) on the Bitcoin network.<br>
<br>
ZKCP is a transaction protocol that allows a buyer to purchase<br>
information from a seller using Bitcoin in a manner which is private,<br>
scalable, secure, and which doesn=E2=80=99t require trusting anyone: the<br=
>
expected information is transferred if and only if the payment is<br>
made. The buyer and seller do not need to trust each other or depend<br>
on arbitration by a third party.<br>
<br>
Imagine a movie-style =E2=80=9Cbriefcase swap=E2=80=9D (one party with a br=
iefcase<br>
full of cash, another containing secret documents), but without the<br>
potential scenario of one of the cases being filled with shredded<br>
newspaper and the resulting exciting chase scene.<br>
<br>
An example application would be the owners of a particular make of<br>
e-book reader cooperating to purchase the DRM master keys from a<br>
failing manufacturer, so that they could load their own documents on<br>
their readers after the vendor=E2=80=99s servers go offline. This type of s=
ale<br>
is inherently irreversible, potentially crosses multiple<br>
jurisdictions, and involves parties whose financial stability is<br>
uncertain=E2=80=93meaning that both parties either take a great deal of ris=
k<br>
or have to make difficult arrangement. Using a ZKCP avoids the<br>
significant transactional costs involved in a sale which can otherwise<br>
easily go wrong.<br>
<br>
In today=E2=80=99s transaction I purchased a solution to a 16x16 Sudoku puz=
zle<br>
for 0.10 BTC from Sean Bowe, a member of the Zcash team, as part of a<br>
demonstration performed live at Financial Cryptography 2016 in<br>
Barbados. I played my part in the transaction remotely from<br>
California.<br>
<br>
The transfer involved two transactions:<br>
<br>
8e5df5f792ac4e98cca87f10aba7947337684a5a0a7333ab897fb9c9d616ba9e<br>
200554139d1e3fe6e499f6ffb0b6e01e706eb8c897293a7f6a26d25e39623fae<br>
<br>
Almost all of the engineering work behind this ZKCP implementation was<br>
done by Sean Bowe, with support from Pieter Wuille, myself, and Madars<br>
Virza.<br>
<br>
<br>
Read more, including technical details at<br>
<a href=3D"https://bitcoincore.org/en/2016/02/26/zero-knowledge-contingent-=
payments-announcement/" rel=3D"noreferrer" target=3D"_blank">https://bitcoi=
ncore.org/en/2016/02/26/zero-knowledge-contingent-payments-announcement/</a=
><br>
<br>
[I hope to have a ZKCP sudoku buying faucet up shortly. :) ]<br>
_______________________________________________<br>
bitcoin-dev mailing list<br>
<a href=3D"mailto:bitcoin-dev@lists.linuxfoundation.org">bitcoin-dev@lists.=
linuxfoundation.org</a><br>
<a href=3D"https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev" =
rel=3D"noreferrer" target=3D"_blank">https://lists.linuxfoundation.org/mail=
man/listinfo/bitcoin-dev</a><br>
</blockquote></div><br></div>

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