A Model Based Approach to Timestamp Evidence Interpretation

A Model Based Approach to Timestamp Evidence Interpretation

Svein Yngvar Willassen (Norwegian University of Science and Technology, Norway)
DOI: 10.4018/978-1-60960-515-5.ch007
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Timestamps play an important role in digital investigations, since they are necessary for the correlation of evidence from different sources. Use of timestamps as evidence can be questionable due to the reference to a clock with unknown adjustment. This work addresses this problem by taking a hypothesis based approach to timestamp investigation. Historical clock settings can be formulated as a clock hypothesis. This hypothesis can be tested for consistency with timestamp evidence by constructing a model of actions affecting timestamps in the investigated system. Acceptance of a clock hypothesis with timestamp evidence can justify the hypothesis, and thereby establish when events occurred in civil time. The results can be used to correlate timestamp evidence from different sources, including identifying correct originators during network trace.
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2. Actions Affect Timestamps

We can build a model of the investigated system, by representing the operations in the system that can possibly change the timestamps as actions. A model of a system with timestamps can then be described as a table listing the timestamps and the actions that affect them. We call this an affects table.

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