Quantum authentication with key recycling
This work addresses secure quantum communication by improving key efficiency, but it is incremental as it builds on prior protocols with enhanced security proofs.
The paper tackles the problem of constructing a secure quantum channel with key recycling in quantum authentication protocols, showing that all secret key bits can be recycled if authentication succeeds and part if tampering is detected, with a proof that the recycled key bits are optimal for this protocol family.
We show that a family of quantum authentication protocols introduced in [Barnum et al., FOCS 2002] can be used to construct a secure quantum channel and additionally recycle all of the secret key if the message is successfully authenticated, and recycle part of the key if tampering is detected. We give a full security proof that constructs the secure channel given only insecure noisy channels and a shared secret key. We also prove that the number of recycled key bits is optimal for this family of protocols, i.e., there exists an adversarial strategy to obtain all non-recycled bits. Previous works recycled less key and only gave partial security proofs, since they did not consider all possible distinguishers (environments) that may be used to distinguish the real setting from the ideal secure quantum channel and secret key resource.