Optimisation of the public key encryption infrastructure for the Internet of Things

The Internet of things (IoT) faces unique security challenges due to its resource constrained devices. Limited processing, storage, memory and power of IoT objects do not support the deployment of advanced security protocols, which are often resource intensive, e.g., the use of Public Key Infrastructure (PKI) to ensures secure end-to-end communications between devices and services over the Internet. There are several approaches in the literature to improve the efficiency of communication protocols employed in PKI environments. Some researchers advocate decreasing the size of the x.509 certificates or fine tuning the DTLS handshake. Others investigated using neighbouring or virtual resources to perform the complex cryptographic algorithms on behalf of IoT constrained devices or using two factor authentication via an authorisation server to delegate authentication and authorisation. This paper surveys attempts in the literature to reduce the overhead incurred by IoT devices running complex PKI security protocols. It is evident from the literature that there is no universal solution for IoT constrained devices, instead, a selection of algorithms and frameworks is needed depending on the levels of interoperability, network scalable needs and ultimately how constrained the IoT devices are.