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SUMMARY:Position-Based Quantum Cryptography: Impossibility and Constructio
 ns - Christian Schaffner (CWI)
DTSTART:20110224T141500Z
DTEND:20110224T151500Z
UID:TALK28468@talks.cam.ac.uk
CONTACT:Ashley Montanaro
DESCRIPTION:We study position-based cryptography in the quantum setting. T
 he aim is to use the geographical position of a party as its only credenti
 al. On the negative side\, we show that if adversaries are allowed to shar
 e an arbitrarily large entangled quantum state\, no secure\nposition-verif
 ication is possible at all. We show a distributed protocol for computing a
 ny unitary operation on a state shared between the different users\, using
  local operations and only one simultaneous round of classical communicati
 on. On the positive side\, we show that if adversaries do not share any en
 tangled quantum state but can compute arbitrary quantum operations\, secur
 e position-verification is\nachievable. In models where secure positioning
  is achievable\, we show that other position-based cryptographic schemes a
 re possible as well\,\nsuch as secure position-based authentication and po
 sition-based key agreement.\n\njoint work with Harry Buhrman\, Nishanth Ch
 andran\, Serge Fehr\, Ran Gelles\, Vipul Goyal and Rafail Ostrovsky.\n\nht
 tp://arxiv.org/abs/1009.2490
LOCATION:MR3\, Centre for Mathematical Sciences
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