Forwarded on behalf of Francois Helt who is temporarily experiencing troubles with the mailing list subscription system. -------- Original Message -------- Subject: Re: Erasure Coding and Homomorphism Date: Fri, 25 Oct 2013 10:43:57 +0200 From: Francois Helt <francois.helt@xxxxxxxxxxxxxxxxx> To: James Plank <plank@xxxxxxxxxx> CC: Loic Dachary <loic@xxxxxxxxxxx> Hello a quick reaction. The papers are interesting indeed. Let me do a rough summary of what I understand and the application requirements I foresee A Client C is entrusting precious and large data to a Server S (or a Service company provinding long-term preservation in our case) The Client is able to generate Keys in such a way that, it is possible to Challenge the Server to verify the presence of the whole data 1) without having to retain the original data on the Client side, 2) the Server being unable to forge a plausible answer 3) with limited network traffic and with efficient data browsing Therefore it is a secure Verifiable Possession of the data by the Server It seems that there is also the possibility that the data is encrypted. This is the first important point for our application: The Service provided for preserving data must be such that data is encrypted and (we) the Server is allways managing data blindly without the possibility to see it clearly - i.e. without the possibility to make illegal copies of the content. The second point is also easy to foresee: The Server must also be able to check the integrity of data it is preserving in order to fight data corruption. Erasure coding might be used in such a way that as soon as recovery of the data is becoming too difficult, there must be an action to regenerate the original data (always encrypted) and redo the erasure coding. If data can be kept encrypted and secured in the described way there is the possibility for the Client to recover its data even if the Service company is going under. The Keys by the Client may serve as indictors for the data that the client owns really. A third point is essential for our application: The erasure coding (and/or encryption if erasure coding is not enough to prevent piracy) must be managed in such a way that it is progressive, the order of chunks of data is preserved.. The data must be arranged keeping the original partition, at boudaries of indicidual images or small group of images. It may be necessary (for the sake of preservation management) that individual images or group of images have to be replaced. It is essential to avoid replacing a whole film if only a small portion is corrupted. Also it may happen that large file should be split in order to fit with backups system sizes. I hope that I am clear enough Francois 2013/10/18 James Plank <plank@xxxxxxxxxx <mailto:plank@xxxxxxxxxx>> Hi Francois and Loic -- sorry to be so long in responding. I'm swamped as always. Is the following paper something like what you're envisioning? http://web.njit.edu/~crix/publications/acm-tissec11a.pdf I think the combination is a powerful one which has seen some application (I know about this one because I was on Osama Khan's phd committee). Perhaps the Store, Forget and Check paper by Ethan Miller does the same thing -- it has been a few years since I have read it: http://www.ssrc.ucsc.edu/pub/schwarz06-icdcs.html Are these having the flavor of what you are proposing? Thanks and best wishes -- Jim ---------- On Oct 11, 2013, at 11:36 AM, Francois Helt wrote: > Hello > > to be a bit more precise and to show the interest of the combination of technologies, the idea is the following > > Combining "Erasure coding" and "Homomorphic encryption" in order to: > - Allow the preservation of cinematographic content with huge size requirements > - Offer a fully secure service as the service provider will never see the decrypted content > - use "homomorphic" coding allowing to work on, recover and manage encrypted content > > > > > 2013/10/11 Loic Dachary <loic@xxxxxxxxxxx <mailto:loic@xxxxxxxxxxx>> > > Hi James, > > Please meet François Helt who is best know for his work on image processing in the movie industry. It has been suggested that there may be interesting intersections between "Homomorphism" and Erasure Coding. Do you have an opinion on this topic ? It is entirely possible that my question does not make any sense :-) Hopefully François will be able to expand in a sensible way. > > Cheers > > P.S. I cc' the public mailing list ceph-devel in the hope that people are willing to participate in this thread. > > -- > Loïc Dachary, Artisan Logiciel Libre > All that is necessary for the triumph of evil is that good people do nothing. > > > > > -- > *François Helt* > Chief Scientific Officer | Highlands Technologies Solutions > > francois.helt@xxxxxxxxxxxxxxxxx <mailto:nicolas.chiovini@xxxxxxxxxxxxxxxxx> > www.h-t-solutions.com <http://www.h-t-solutions.com/> > > <image002.jpg> > > 1900 route des Crêtes - BP 298 > 06905 Sophia Antipolis Cedex, France > > -------------------- > P /!! 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