Treffer: Co-design for Security and Reliability

Security is commonly defined as the preservation of three system properties: confidentiality, which is the ability to prevent an unauthorized party from reading data; integrity, which is the ability to prevent an unauthorized party from writing data; and availability, which is the ability of an authorized party to use the system free of interference from an unauthorized party. Simply put, security mechanisms and policies are designed to keep unauthorized parties out of the system. On the other hand, reliability is defined as a system’s ability to operate as intended under non-adversarial conditions. It is measured as the probability of producing correct outputs at any given time. In the design of the reliability technique, one assumes that things that cause reliability failures (e.g., cosmic rays) do not seek to bypass reliability-enhancing mechanisms and policies. On the other hand, security mechanisms are designed assuming the attackers will attempt to circumvent them by exploiting any design or implementation weaknesses. From the above definitions, it may appear that reliability mechanisms should be built after security mechanisms since non-adversarial conditions can be enabled only with strong security mechanisms. However, for security mechanisms to operate as intended, they need to do so under both adversarial and non-adversarial conditions; thus, security mechanisms themselves are required to be reliable. This creates a chicken-and-egg situation that can only be resolved by co-designing security and reliability techniques together. However, due to historical reasons and engineering rationales, reliability features and security solutions are designed in isolation, often competing for the same resources and leading to trade-offs that may compromise both system reliability and security. Moreover, security today is layered on top of reliability. A justification for this may be that a system has to become reliable for it to attract users and thus become attack-worthy: an unreliable system is as useless to ...