  Utilizing the advantage of quantum entanglement swapping, a multi-party
quantum key agreement protocol with authentication is proposed. In this
protocol, a semi-trusted third party is introduced, who prepares Bell states,
and sends one particle to multiple participants respectively. After that the
participants can share a Greenberger-Horne-Zeilinger state by entanglement
swapping. Finally, these participants measure the particles in their hands and
obtain an agreement key. Here, classical hash function and Hadamard operation
are utilized to authenticate the identity of participants. The correlations of
GHZ states ensure the security of the proposed protocol. To illustrated it
detailly, the security of this protocol against common attacks is analyzed,
which shows that the proposed protocol is secure in theory.
