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SUMMARY:Efficient Cryptography for the Next Generation Secure Cloud - Alpt
 ekin Küpçü\, Koç University
DTSTART:20120417T150000Z
DTEND:20120417T160000Z
UID:TALK37622@talks.cam.ac.uk
CONTACT:Microsoft Research Cambridge Talks Admins
DESCRIPTION:Peer-to-peer (P2P) systems\, and client-server type storage an
 d computation outsourcing constitute some of the major applications that t
 he next generation cloud schemes will address.  Since these applications a
 re just emerging\, it is the perfect time to design them with security and
  privacy in mind. Furthermore\, considering the high-churn characteristics
  of such systems\, the cryptographic protocols employed must be efficient 
 and scalable.\n\nIn this talk\, I will focus on an efficient and scalable 
 fair exchange protocol that can be used for exchanging files between parti
 cipants of a P2P file sharing system. It has been shown that fair exchange
  cannot be done without a trusted third party (called the Arbiter). Yet\, 
 even with a trusted Arbiter\, it is still non-trivial to come up with an e
 fficient solution\, especially one that can be used in a P2P file sharing 
 system with a high volume of data exchanged. Our protocol is optimistic\, 
 removing the need for the Arbiter's involvement unless a dispute occurs. W
 hile the previous solutions employ costly cryptographic primitives for eve
 ry file or block exchanged\, our protocol employs them only once per peer\
 , therefore achieving O(n) efficiency improvement when n blocks are exchan
 ged between two peers.\nIn practice\, this corresponds to one-two orders o
 f magnitude improvement in terms of both computation and communication (42
  minutes vs. 40 seconds\, 225 MB vs. 1.8 MB). Thus\, for the first time\, 
 a provably secure (and privacy respecting when payments are made using\ne-
 cash) fair exchange protocol is being used in real bartering applications 
 (e.g.\, BitTorrent) without sacrificing performance.\n\nFinally\, if time 
 permits\, I will briefly mention some of our other results on cloud securi
 ty including ways to securely outsource computation and storage to untrust
 ed entities\, official arbitration in the cloud\, impossibility results on
  distributing the Arbiter\, keeping the user passwords safe\, and the Brow
 nie Cashlib cryptographic library including ZKPDL zero-knowledge proof des
 cription language we have developed. I will also be available to talk on t
 hese other projects after the presentation.
LOCATION:Primrose Room\, Microsoft Research Ltd\, 7 J J Thomson Avenue (Of
 f Madingley Road)\, Cambridge
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