  As the number of digital documents requiring investigation increases, it has
become more important to identify relevant documents to a given case. There
have been continual demands for finding relevant files in order to overcome
this kind of issues. Regarding finding similar files, there can be a situation
where there is no available metadata such as timestamp, file size, title,
subject, template, author, etc. In this situation, investigators will focus on
searching document files having specific keywords related to a given case.
Although the traditional keyword search with elaborate regular expressions is
useful for digital forensics, there is a possibility that closely related
documents are missing because they have totally different body contents. In
this paper, we introduce a recent actual case on handling large amounts of
document files. This case suggests that similar layout search will be useful
for more efficient digital investigations if it can be utilized appropriately
for supplementing results of the traditional keyword search. Until now,
research involving electronic-document similarity has mainly focused on byte
streams, format structures and body contents. However, there has been little
research on the similarity of visual layouts from the viewpoint of digital
forensics. In order to narrow this gap, this study demonstrates a novel
framework for retrieving electronic document files having similar layouts, and
implements a tool for finding similar Microsoft OOXML files using
user-controlled layout queries based on the framework.
