Defining Atomicity (and Integrity) for Snapshots of Storage in Forensic Computing

This paper revisits and refines the quality criteria for forensic memory acquisition, introducing new formal definitions of atomicity—instantaneous and quasi-instantaneous consistency—that better reflect real-world constraints during snapshotting. It also proposes a refined integrity concept and suggests practical evaluation methods to improve forensic analysis reliability. #Atomicity #QuasiInstantaneousConsistency #MemorySnapshot #ForensicIntegrity

Keypoints

Introduces two new atomicity definitions, instantaneous and quasi-instantaneous consistency, to better capture snapshot quality during live forensic memory acquisition.
Quasi-instantaneous consistency allows snapshots without system freezing, assuming values could have existed simultaneously in memory at some time point.
Refines the concept of integrity from a restrictive to a more permissive definition, allowing for selective memory changes during acquisition when original values are preserved.
Causal consistency, previously the main atomicity criterion, is shown to be too permissive and sometimes unattainable in practical scenarios.
Proposes vector clock mechanisms to track and measure snapshot consistency and causal relationships among memory regions for evaluation purposes.
Discusses practical techniques such as copy-on-write and hypervisor-assisted snapshots to achieve quasi-instantaneous consistency during live memory acquisition.
Highlights the legal importance of using forensic tools that guarantee high atomicity and integrity to maintain evidential value of memory snapshots in investigations.

Security Problem
The paper addresses the challenge of acquiring forensic memory snapshots that preserve evidential integrity and correctness in systems that cannot be frozen, such as live production servers or devices under high load. Traditional notions of atomicity and consistency in snapshots often fail in these environments, risking inconsistent or invalid forensic data that could undermine the reliability of digital investigations.

Methodology or Data
The authors revisit existing theoretical frameworks and propose formal definitions for instantaneous and quasi-instantaneous consistency based on causality and real-time information. They use models from distributed computing, such as space/time diagrams and vector clocks, to describe and analyze snapshot atomicity. The paper also outlines practical approaches like copy-on-write and hypervisor-assisted memory acquisition and describe plans to implement and evaluate these concepts using concurrency-aware test programs.

Key Findings
The research establishes that quasi-instantaneous consistency is a realistic and attainable compromise between the ideal of instantaneous snapshots and more permissive causal consistency, allowing snapshots to be meaningful without system freezing. It also shows the refined permissive integrity definition better aligns with operational realities by permitting transient memory changes if original values are retained at a reference time. Moreover, vector clocks provide a feasible method to detect atomicity violations and inconsistencies in live snapshots.

Operational Relevance
These new definitions and evaluation techniques enable forensic practitioners and SOC teams to better assess the quality and reliability of memory snapshots collected from live systems, guiding tool selection and acquisition strategies. Understanding atomicity and integrity levels helps anticipate inconsistencies that could affect analysis outcomes or evidentiary value, which is critical for court-admissible digital evidence. Furthermore, the proposed measurement frameworks allow ongoing assessment and benchmarking of forensic acquisition tools in realistic environments.

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