Anonymous Communication in Quantum Networks

Abstract

In this dissertation, we explore the protocols enabling anonymous communication in quantum networks i.e. transmission of qubits from sender to receiver by creating or distributing Entangled states between them without disclosing their identities as sender or receiver to the other parties in the network. Existing methods uses classical, as well as quantum subprotocols to achieve anonymity.The Quantum sub-protocols include protocols for anonymous entanglement distribution using GHZ states, verification (not device-independent) of GHZ state that requires secure private classical channels, techniques for ϵ-anonymity(i.e. the other parties can at most guess a little ϵ amount better than a random guess about who the sender is, due to little impurity in the GHZ state used as a resource).The existing classical sub-protocols also uses secure private classical channels for communication, which is costly to make completely secure. Our contributions include quantum versions of Classical sub-protocols for tasks such as parity(for calculating Boolean-XOR of the input bits of all the parties in the network), logical-OR(for calculating Boolean-OR), Notification done anonymously (i.e. not revealing the input of each party to other parties) without requiring secure private classical channels and device-independent verification (also without requiring secure private classical channels) of GHZ state (of odd number of parties) used as a resource in the sub-protocols. Formal proofs and security analyses demonstrate that our protocols meet the desired anonymity and correctness guarantees. This work lays the groundwork for future anonymous quantum communication systems.