Researchers experimentally demonstrated five information-theoretically secure anonymity protocols on an eight user city-wide quantum network using polarisation entangled photon pairs.
Anonymity in networked communication is vital for many privacy-preserving tasks. Secure key distribution alone is insufficient for high-security communications.
At the heart of these protocols is anonymous broadcasting, which is a cryptographic primitive that allows one user to reveal one bit of information while keeping their identity anonymous. For a network of n users, the protocols retain anonymity for the sender, given that no more than n − 2 users are colluding.
This is an implementation of genuine multi-user cryptographic protocols beyond standard QKD.
These anonymous protocols enhance the functionality of any fully-connected Quantum Key Distribution network without trusted nodes.
The paper has been published in npj Quantum Information.