  Quantum communication networks are connected by various devices to achieve
communication or distributed computing for users in remote locations. In order
to solve the problem of generating temporary session key for secure
communication in optical-ring quantum networks, a quantum key agreement
protocol is proposed. In the key agreement protocols, an attacker can
impersonate a legal user to participate in the negotiation process and
eavesdrop the agreement key easily. This is often overlooked in most quantum
key agreement protocols, which makes them insecure in practical implementation.
Considering this problem, the function of authenticating the user's identity is
added in the proposed protocol. Combining classical hash function with identity
information, we design the authentication operation conforming to the
characteristics of quantum search algorithm. In the security analysis of the
proposed protocol, quantum state discrimination is utilized to show that the
protocol is secure against common attacks and impersonation attack. In
addition, only single photons need to be prepared and measured, which makes our
protocol feasible with existing technology.
