Exploring the space of digital evidence: Position paper

Digital evidence is much more than what is acquired during forensic investigations. In particular when building systems that are supposed to provide secure digital evidence it is necessary to clearly define requirements. Various work on forensic evidence provides different sets of such requirements. Also ISO standardization work is concerned with forensic evidence. However, currently there is no full overview of the different relevant areas for digital evidence that can be used for guidance in the requirement phase of system engineering. Furthermore, a rigorous specification of requirements for digital evidence is missing. Formal methods have been applied to security protocols and other types of requirements, but not to describe the various requirements of digital evidence. One approach towards defining the available space for digital evidence suggests three dimensions. First, and most obviously, is the time when data is collected, processed, retained and correlated for potential forensic use. This dimension includes data collected at run-time, data collected for particular transactions, in case of deviations, for incidents, “postmortem” forensic investigations, and the digitization of evidence for court procedures. The second dimension describes the goal for which digital evidence is produced. This can be either for showing compliance, i.e. for proving that somebody was not responsible for some incident or for showing malicious events that happened and to find who did what. Finally, the third dimension consists of the actual information to be documented. Examples are the documentation of the normal system behaviour, compliance information, accidents, safety issues, malicious behaviour, identity information and various relevant parameters. A formal framework for security requirements that was developed for security requirements engineering is one promising candidate to derive a precise characterization of requirements for digital evidence in the different areas of the available evidence space. This paper is a position paper to drive the discussion and development in forensic readiness and security of digital evidence.