Abstract
Authentication by key is successfully applied in many cases. However, this simple approach raises several problems during contextual authentication, when the final decision depends not only on the knowledge of the key but also on some other independent parameters such as time, distance, values fetched from nearby internet of things (IoT) devices, etc. Such contextual parameters are usually considered an independent phase of the whole authentication process. In this paper, we propose a new method of extended authentication because, instead of using just keys, we also applied some mathematical formulas describing the context to be evaluated as a single cryptographic process.