|
The digitization of physical traces from crime scenes in forensic investigations in effect creates a digital chain-of-custody and entrains the challenge of creating a link between the two or more representations of the same
trace. In order to be forensically sound, especially the two security aspects of integrity and authenticity need
to be maintained at all times. Especially the adherence to the authenticity using technical means proves to
be a challenge at the boundary between the physical object and its digital representations. In this article we
propose a new method of linking physical objects with its digital counterparts using two-dimensional bar codes
and additional meta-data accompanying the acquired data for integration in the conventional documentation
of collection of items of evidence (bagging and tagging process). Using the exemplary chosen QR-code as
particular implementation of a bar code and a model of the forensic process, we also supply a means to integrate
our suggested approach into forensically sound proceedings as described by Holder et al.1 We use the example of
the digital dactyloscopy as a forensic discipline, where currently progress is being made by digitizing some of the
processing steps. We show an exemplary demonstrator of the suggested approach using a smartphone as a mobile
device for the verification of the physical trace to extend the chain-of-custody from the physical to the digital
domain. Our evaluation of the demonstrator is performed towards the readability and the verification of its
contents. We can read the bar code despite its limited size of 42 x 42 mm and rather large amount of embedded
data using various devices. Furthermore, the QR-code's error correction features help to recover contents of
damaged codes. Subsequently, our appended digital signature allows for detecting malicious manipulations of
the embedded data.
|
