Hybrid Logical Clocks for Database Forensics: Filling the Gap between Chain of Custody and Database Auditing

Database audit records are important for investigating suspicious actions against transactional databases. Their admissibility as digital evidence depends on satisfying Chain of Custody (CoC) properties during their generation, collection and preservation in order to prevent their modification, guarantee action accountability, and allow third-party verification. However, their production has relied on auditing capabilities provided by commercial database systems which may not be effective if malicious users (or insiders) misuse their privileges to disable audit controls, and compromise their admissibility. Hence, in this paper, we propose a forensically-aware distributed database architecture that implements CoC properties as functional requirements to produce admissible audit records. The novelty of our proposal is the use of hybrid logical clocks, which compared with a previous centralised vector-clock architecture, has evident advantages as it (i) allows for more accurate provenance and causality tracking of insider actions, (ii) is more scalable in terms of system size, and (iii) although latency is higher (as expected in distributed environments), 70 per cent of user transactions are executed within acceptable latency intervals.