ML4Q researchers from Düsseldorf (Bruss group) have published a paper in PRX Quantum on Quantum Conference Key Agreement.
Congratulations to all the authors on their impressive results!
Federico Grasselli, Gláucia Murta, Jarn de Jong, Frederik Hahn, Dagmar Bruß, Hermann Kampermann, and Anna Pappa
Secure Anonymous Conferencing in Quantum Networks
PRX Quantum 3, 040306 – Published 13 October 2022
Quantum conference key agreement (CKA) enables quantum network users to generate a secret encryption key, which is shared between a sender and multiple receivers, for group-wide secure communication. However, standard CKA requires the sender and the receivers to publicly disclose their identities, which may be undesirable depending on the nature of the communication. Anonymous CKA aims at protecting the identities of the communicating users such that they remain unknown to everyone except for the sender, who initiates the communication.
In our work, we introduce a security framework for anonymous CKA with different degrees of anonymity, inspired by the well-established security framework of quantum key distribution. Moreover, we design protocols for anonymous CKA that are based on the distribution of multipartite entangled states, known as Greenberger-Horne-Zeilinger (GHZ) states, between all network users. The intrinsic nonclassical correlations provided by GHZ states ensure that our protocols are efficient and noise tolerant.
In addition, we prove the security of our protocols under general attacks by an eavesdropper with unbounded quantum power and analyze their performance in noisy and lossy quantum networks. The simulations show that our GHZ-based protocols can outperform anonymous CKA protocols that only use bipartite entanglement and that the advantage increases for protocols with stronger anonymity requirements.
In summary, our work significantly advances the field of quantum cryptography by formalizing the task of anonymous CKA, equipping it with a security framework and providing protocols that go beyond quantum key distribution through the use of multipartite entanglement.