  Authentication is one of the essential security services in Wireless Sensor
Networks (WSNs) for ensuring secure data sessions. Sensor node authentication
ensures the confidentiality and validity of data collected by the sensor node,
whereas user authentication guarantees that only legitimate users can access
the sensor data. In a mobile WSN, sensor and user nodes move across the network
and exchange data with multiple nodes, thus experiencing the authentication
process multiple times. The integration of WSNs with Internet of Things (IoT)
brings forth a new kind of WSN architecture along with stricter security
requirements; for instance, a sensor node or a user node may need to establish
multiple concurrent secure data sessions. With concurrent data sessions, the
frequency of the re-authentication process increases in proportion to the
number of concurrent connections, which makes the security issue even more
challenging. The currently available authentication protocols were designed for
the autonomous WSN and do not account for the above requirements. In this
paper, we present a novel, lightweight and efficient key exchange and
authentication protocol suite called the Secure Mobile Sensor Network (SMSN)
Authentication Protocol. In the SMSN a mobile node goes through an initial
authentication procedure and receives a re-authentication ticket from the base
station. Later a mobile node can use this re-authentication ticket when
establishing multiple data exchange sessions and/or when moving across the
network. This scheme reduces the communication and computational complexity of
the authentication process. We proved the strength of our protocol with
rigorous security analysis and simulated the SMSN and previously proposed
schemes in an automated protocol verifier tool. Finally, we compared the
computational complexity and communication cost against well-known
authentication protocols.
