Evaluation of Public Key Certificate Enrolment in Resource Constraint Embedded Field Devices

A Public Key Infrastructure (PKI) is a strong security fundament to secure device-to-device communication. However, the management and the processing of public key certificates in small embedded devices is a major challenge. There are different protocols available for automated certificate enrolment with a PKI. Among them, Enrolment over Secure Transport (EST) is one of the widely used and more secure enrolment protocols. Constraint devices use Constraint Application Protocol (CoAP) for message transport. This paper focuses on the evaluation of such a certificate provisioning protocol called EST over secure CoAP(EST-Coaps), which is primarily designed for constrained IoT devices. The deployment model incorporates the field devices, a deployment agent and a credential authority. Field devices need to interact with the Credential Authority (CA), in order to obtain Site Credentials. More precisely, this paper analyses the performance of EST_Coaps in terms of scalability and security.