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On Dec 20, 2014 8:49 AM, "Peter Todd" <<a href="mailto:pete@petertodd.org">pete@petertodd.org</a>> wrote:<br>
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> However the converse is not possible: anti-replay cannot be used to implement proof-of-publication. Knowing that no conflicting message exists says nothing about who be in posession of that message, or indeed, any message at all. Thus anti-replay is not sufficient to implement other uses of proof-of-publication such as decentralized exchange³.</p>
<p dir="ltr">How does proof of publication prove who is in possession of that message? Or of any message at all? The data written in an anti-replay system and the data written in a proof of publication system differs in that you can't repeat data in an anti-replay system according to some understanding of the rules of the meaning of the data (if I am following your description correctly). </p>
<p dir="ltr"> Obviously you can publish the same data as many times as you like in a proof-of-publication system; the interpretation of what that data means would be the responsibility of the observers, not the "publishing vehicle". Repeated entries thus can be written, and the user of PoP can validate and prove they did so.</p>
<p dir="ltr">If the data itself defines possession, the "ownership of the message" (it isn't even clear to me what you mean by that phrase) isn't defined by either proof, but by the message itself. And the message itself isn't constrained by either to prohibit proving ownership (what ever you mean by that).</p>
<p dir="ltr">Of course, I do assume I can test a message (or a set of messages sharing some feature like a particular input on a transaction) as being publishable in an anti-replay system without actually publishing it. That does allow one to prove non-publishing. You can determine if a message exists that would preclude the publishing of a message; the very purpose of an anti-replay proof. </p>
<p dir="ltr">And I would assert that such a search (i.e. the idea that such a search has meaning in a anti-replay system) is already incorporating the assumption that such a search is possible and must be possible for an anti-replay system.</p>