Context-aware cryptographic policy for event-driven architectures: encryption based on event importance

Abstract

The article discusses an approach to building a context-oriented cryptographic policy for event-driven systems in which data exchange is implemented through asynchronous events, streams, and logs (log-based integration). Such systems generate huge volumes of heterogeneous events with varying criticality and confidentiality requirements. In such architectures, events are often delivered according to the at-least-once semantics, duplicated when repeated, stored for a long time in brokers/repositories, transferred between domains, and reproduced to restore the state. This increases the risks of compromising confidentiality and integrity, and also creates practical prerequisites for nonce/IV usage errors in authenticated encryption modes with attached data. The main idea of the work is to formalize the «importance of an event» as a policy attribute that guides the choice of a cryptographic profile (encryption algorithm, nonce strategy, associated data policy, key rotation, anti-replay mechanisms) taking into account limited resources (execution time, memory, energy consumption, overhead bytes, and network constraints). Existing approaches to event classification and selective encryption mechanisms are analyzed. A model of events and context, an importance function, a cost model, and a risk model are proposed, as well as an optimization problem of “minimizing costs under risk constraints” for automated selection of a protection profile. The scientific novelty lies in combining the principles of Authenticated Encryption with Associated Data and Attribute-Based Access Control approach to policies and hierarchical key management in a unified policy framework that takes into account the duplicates/retries/long-term storage of events characteristic of event-driven systems and introduces semantic integrity through authentication of the delivery context as part of associated data. The practical significance lies in the proposed policy templates for different levels of importance (L0–L3), as well as the methodology for domain isolation of keys and short cryptographic epochs, which reduce the consequences of compromise. An algorithm for dynamic determination of cryptographic parameters based on event priority has been developed. It is shown that adaptive encryption «by event importance» reduces cryptographic overhead in high-frequency streams without degrading the security of critical events, providing a manageable trade-off between risk and resources.