Quantum Computation and Information Seminar 

18/04/2008, 15:00 — 16:00 — Room P4.35, Mathematics Building
Francisco Marcos de Assis, U Federal de Campina Grande

Security Analysis of a Quantum-Classical Authentication Protocol

We present a quantum-classical version of a well-known classical message authentication protocol, proposed originally by Brassard. The Brassard protocol utilizes two secret keys: one of these keys specifies a fixed universal-2 hash function and the other one specifies the seed of pseudo-random generator. The algorithm works as follows: for each message it calculates a tag using the hash function pointed by the first secret key and then transmits the tag XORed with the pseudo-random sequence from the pseudo-random generator initialized with the other key. The protocol offers computational security. Our quantum-classical version of this protocol replaces the XOR operation by an BB84-like encoding of the tag. We explore the potential advantages of our protocol over the purely classical one.