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Inside Out

Paper on new evidence container format accepted for presentation at DFRWS2009

Michael Cohen, Simson Garfinkel and I have been collaborating recently on the development of a new digital evidence storage container format. Today we have had notification that a paper detailing the research behind this development has been accepted at the 2009 Digital Forensics Research Workshop, to be held in Montreal Canada. The title of the paper is “Extending the Advanced Forensic Format to accommodate Multiple Data Sources, Logical Evidence, Arbitrary Information and Forensic Workflow”.

A new evidence container is sorely needed by the computer forensics community, due to the large amount of manual work currently required in managing evidence and the closed nature of the current generation of forensic containers and tools. With this new forensic container, we provide an open and extensible container standard which promotes forensic tool interoperability and simplifies evidence sharing and management.

Technically, this new container achieves these things by enabling:

  • efficient random access storage of multiple streams of digital evidence within a single container;
  • storage of arbitrary information such as case relevant information or tool derived analysis results;
  • composition of evidence containers into a larger corpus of related evidence through an inter container referencing scheme;
  • decomposition of evidence containers into sets of smaller containers to support filesystem limitations;
  • definition of virtual evidence streams as maps of existing evidence streams.

The new format is slated to replace the current generation of Simson’s Advanced Forensic Format (AFF) and will be known as AFF4. Michael has been providing some documentation on the format over at the forensicswiki, and he has a beta quality implementation in the C language. Plans are in place for a JAVA based parallel implementation.

The abstract follows:

Forensic analysis requires the acquisition and management of many different types of evidence, including individual disk drives, RAID sets, network packets, memory images, and extracted files. Often the same evidence is reviewed by several different tools or examiners in different locations. We propose a backwards-compatible evolutionary redesign of the Advanced Forensic Format—an open, extensible file format for storing and sharing of evidence, arbitrary case related information and analysis results among different tools. The new specification was designed to be simple to implement, allowing the use of the well supported Zip File format specifications for bit level file access.

UPDATE: The paper is now published on the DFRWS 2009 website.