Fully device-independent conference key agreement

Abstract

We present the first security analysis of conference key agreement (CKA) in the most adversarial model of device independence (DI). Our protocol can be implemented {by any experimental setup} that is capable of performing Bell tests (specifically, we introduce the "Parity-CHSH" inequality), and security can in principle be obtained for any violation of the Parity-CHSH inequality. We use a direct connection between the $N$-partite Parity-CHSH inequality and the CHSH inequality. Namely, the Parity-CHSH inequality can be considered as a CHSH inequality or another CHSH inequality (equivalent up to relabelling) depending on the parity of the output of $N-2$ of the parties. We compare the asymptotic key rate for DICKA to the case where the parties use $N-1$ DIQKD protocols in order to generate a common key. We show that for some regime of noise the DICKA protocol leads to better rates.