Security can be seen as an optimisation objective in NoC resource management, and as such poses trade-offs against other objectives such as real-time schedulability. In this paper, we show how to increase NoC resilience against a concrete type of security attack, named side-channel attack, which exploit the correlation between specific non-functional properties (such as packet latencies and routes, in the case of NoCs) to infer the functional behaviour of secure applications. For instance, the transmission of a packet over a given link of the NoC may hint on a cache miss, which can be used by an attacker to guess specific parts of a secret cryptographic key, effectively weakening it. We therefore propose packet route randomisation as a mechanism to increase NoC resilience against side-channel attacks, focusing specifically on the potential impact of such an approach upon hard real-time systems, where schedulability is a vital design requirement. Using an evolutionary optimisation approach, we show how to effectively apply route randomisation in such a way that it can increase NoC security while controlling its impact on hard real-time performance guarantees. Extensive experimental evidence based on analytical and simulation models supports our findings.
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