Ranendu Adhikary

Conference key agreement allows multiple parties to establish a shared secret key. Device-independent protocols are especially attractive because their security can be certified from observed correlations, without trusting the internal behavior of the devices. We propose a tripartite device-independent conference key agreement protocol using only two measurement bases on a shared GHZ state. Under suitable structural conditions, the maximal violation of a chosen Bell inequality self-tests the target GHZ strategy with Pauli measurements, ensuring ideal security. We also prove robust self-testing, showing that near-maximal violation guarantees nontrivial fidelity with the ideal strategy under realistic noise.