A system and method of authenticating a communication network comprising a first computing device, a second computing device and an intermediary computing device, wherein there is a first path between the first computing device and the intermediary computing device and a second path between the second computing device and the intermediary computing device. The method is executed at the intermediary computing device, and comprises receiving, from the first computing device, a first session key generated by the first computing device using a function, wherein an input to the function comprises an incremented variable; receiving, from the second computing device, data associated with a second session key generated by the second computing device using the function; determining that the first session key and the second session key are the same; and defining the communication network as authentic when the first session key and the second session key are the same.