An Automatic Key Generator based on Physical Functions for Resource Constrained Nodes in Future Wireless Sensor Networks

Nodes in Wireless Sensor Networks (WSN) perform every day more critical operations. Originally, sensor nodes were connected in closed networks, where they only collected data and sent them to a central server to be processed. However, with the arrival of the fourth industrial revolution and the era of Cyber-Physical Systems, Wireless Sensors Networks are employed in a large catalogue of applications, many of them critical: traceability, ambient intelligence, biological signal control, etc. At the beginning, simple encryption techniques were enough, but as more sophisticated applications are proposed, protection schemes turn also more complex. In particular, schemes based on digital signatures, hash functions and Public Key Infrastructures are extensively implemented. Nevertheless, all these solutions present a very important problem: nodes must store a secret key. As future systems will be unmanaged and be deployed in remote places without surveillance, the use of ROM memories where keys are stored in a permanent way is a critical risk. Therefore, in this paper we propose a new scheme for signature delegation in WSN, based on magnetic Physical Unclonable Functions (PUF). PUF take advantage of any physical properties to build private keys which are inaccessible and impossible to replicable; what added to the intrinsic complexity magnetic phenomena will enable us to define an inviolable signature scheme. A simulation scenario is also defined to validate the usability and performance of the proposed framework.