Multipath Authentication without shared Secrets and with Applications in Quantum Networks

Authentication is possible in various ways, the most obvious of which is by re-calculating a given authentication tag upon a private secret shared only with the message’s origin. What, however, if no such shared secrets are available? Public-key cryptography has elegantly solved the problem by relying on computational intractability assumptions. In the light of increasing computational power, can we achieve the same thing in the secret-key paradigm? In a quantum network, we may have shared secrets between adjacent nodes, making an authentic communication between these simple, but what about end-to-end authentication? We present a simple method of authenticating a transmission that requires shared secrets only between neighboring nodes in a (quantum) network, but the sender and receiver (being farther apart) do not need to share any secret knowledge. Our approach is inspired by multipath transmission and thus naturally compatible with this paradigm. The security of the proposed method is analyzed based on decision-theoretic considerations, and therefore does not hinge on any computational intractability assumption.