Biblio

This work proposes a scheme to detect, isolate and mitigate malicious disruption of electro-mechanical processes in legacy PLCs where each PLC works as a finite state machine (FSM) and goes through predefined states depending on the control flow of the programs and input-output mechanism. The scheme generates a group-signature for a particular state combining the signature shares from each of these PLCs using \$(k,\textbackslashtextbackslash l)\$-threshold signature scheme.If some of them are affected by the malicious code, signature can be verified by k out of l uncorrupted PLCs and can be used to detect the corrupted PLCs and the compromised state. We use OpenPLC software to simulate Legacy PLC system on Raspberry Pi and show İ/O\$ pin configuration attack on digital and pulse width modulation (PWM) pins. We describe the protocol using a small prototype of five instances of legacy PLCs simultaneously running on OpenPLC software. We show that when our proposed protocol is deployed, the aforementioned attacks get successfully detected and the controller takes corrective measures. This work has been developed as a part of the problem statement given in the Cyber Security Awareness Week-2017 competition.

Remote Attestation ( RA) is a security service that enables a trusted verifier ( Vrf) to measure current memory state of an untrusted remote prover ( Prv). If correctly implemented, RA allows Vrf to remotely detect if Prv's memory reflects a compromised state. However, RA by itself offers no means of remedying the situation once P rv is determined to be compromised. In this work we show how a secure RA architecture can be extended to enable important and useful security services for low-end embedded devices. In particular, we extend the formally verified RA architecture, VRASED, to implement provably secure software update, erasure, and system-wide resets. When (serially) composed, these features guarantee to Vrf that a remote Prv has been updated to a functional and malware-free state, and was properly initialized after such process. These services are provably secure against an adversary (represented by malware) that compromises Prv and exerts full control of its software state. Our results demonstrate that such services incur minimal additional overhead (0.4% extra hardware footprint, and 100-s milliseconds to generate combined proofs of update, erasure, and reset), making them practical even for the lowest-end embedded devices, e.g., those based on MSP430 or AVR ATMega micro-controller units (MCUs). All changes introduced by our new services to VRASED trusted components are also formally verified.