Hi all,
today Vilasini will talk about composable security in relativistic
quantum cryptography, at the usual time and place (see subject line).
This is joint work with Christopher and Lídia, and is part of her
master thesis. It's also a rehearsal talk for a conference in Oxford
next week, so all feedback is welcome!
Abstract:
Cryptographic resources should remain secure even when used as a
subroutine within arbitrary protocols: they should be composably
secure. It is this notion of security that allows us to construct
cryptographic resources and protocols from each other (e.g. a quantum
key distribution protocol uses an authenticated classical channel and
an insecure quantum channel to construct a shared, secret key resource
between two parties).
While composable security has been widely studied in non-relativistic
cryptography, a general framework for modelling composable security of
classical, quantum and relativistic protocols against classical,
quantum and non-signalling adversaries is lacking. Here we propose a
general framework to this effect and use it to prove novel possibility
and impossibility results in relativistic quantum cryptography.
In particular, we show that even in a relativistic setting, composable
bit commitment is impossible without additional assumptions, and that
both bit commitment and coin flipping can be constructed from the
primitive channel with delay. Our approach applies the formalism of
abstract cryptography to causal boxes.
Best,
-joe