Conference key-agreement and secret sharing through noisy GHZ states
by
Kai Chen
Dept. of Physics, University of Toronto
Coauthors: Hoi-Kwong Lo

Various protocols (BB84, Ekert91, B92) and security proofs for two-party common key-agreement have been proposed. We consider here two quantum communication protocols involving 3 parties in the noisy channel setting. The first cryptographic task is for Alice, Bob and Charlie to establish a secure conference key from noisy tripartite Greenberger-Horne-Zeilinger (GHZ) states in the presence of an eavesdropper. The second cryptographic task is for Alice to share a secret with Bob and Charlie by using noisy GHZ states. We use prepare-and-measure protocols where a preparer prepares an ensemble of GHZ states and distribute them to the three parties through some noisy channels. The three parties only need to perform quantum measurements and, subsequently, classical computations and classical communications. In other words, the three users do not need to perform quantum computation or long-term storage of quantum signals. Therefore, our protocol may be feasible with near-future technology.

Paper reference: arXiv:quant-ph/0404133

Date received: March 22, 2004