February 22, Wednesday 14:15, Room 570, Education Building
Position-based cryptography uses the geographic position of a party
as its sole credential. Normally digital keys or biometric features are
used. A central building block in position-based cryptography is that
of position-verification. The goal is to prove to a set of verifier
that one is at a certain geographical location. Protocols typically
assume that messages can not travel faster than the speed of light. By
responding to a verifier in a timely manner one can guarantee that one
is within a certain distance of that verifier. Quite recently it was
shown that position-verification protocols only based on this
relativistic principle can be broken by two attackers who simulate
being at a the claimed position while physically residing elsewhere in
space.
Because of the no-cloning property of quantum information (qubits) it
was believed that with the use of quantum messages one could devise
protocols that were resistant to such collaborative attacks. Several schemes were proposed
that later turned out to be insecure. Finally it was shown that also in the quantum case no
unconditionally secure scheme is possible.
We will review the field of position-based quantum cryptography and
highlight some of the research currently going on in order to
develop, using reasonable assumptions on the capabilities of the
attackers, protocols that are secure in practice.