The increasing number of Internet of Things (IoT) deployments require lightweight, secure communication and effective scalable management of low-cost IoT devices. This study extends and adapts the Isawa-Morii OTP protocol to provide authentication and key exchange simultaneously. A use case scenario for the extended protocol is presented in order to exemplify symmetric encryption based communication and management of IoT devices. The security of the modified protocol has been formally proven with the AVISPA model checker. Consequently, centrally managed IoT deployments could be handled solely by combinatorial logic and hash functions for authentication, key exchange, and data transfer.