Criminalistics and Forensics Institute: We Have Been Analysing Digital Signatures Since 2012

What is DVP?

"DVP" is an abbreviation for the term "digital handwritten signature." It refers to a signature that is not typically made on paper but rather on or through a digitization device (digitizer), such as a tablet, signature pad, mobile device, using a stylus, touchscreen pen, and similar. This device, in collaboration with specialized software, encodes the movement during signature creation into numerical data; we also use the term "biometric data." If the goal is to sign an electronic document, this data is integrated into the document designated for signing, and encryption ensures the signing of the specific document by the given DVP. This results in an original document with a so-called biometric container. The numerical data constituting DVP can be captured and stored for other purposes, such as creating a client reference database or for graphological examination purposes as DVP tests.

Since we are talking about a handwritten signature, similarly to the case of a traditional paper signature, it is a specific manifestation of the signer's behavior, which, however, does not exist physically on a substrate, such as paper, but digitally in the form of numerical data.

The basic numerical data that constitute DVP are information about the shape of the signature, the so-called static signature characteristics, as well as about the pressure exerted by the signer during signature creation, and the time course of signature creation. From this data, a large amount of additional signature-related information can be calculated, which is important for graphological examination. DVP is the subject of graphological examination precisely because it still represents the manifestation of individual signing behavior, similar to a traditional paper signature, even though we obtain information about it in a different way. Similarly, scientific basis and methods of graphological examination are applied when examining DVP.

In connection with DVP, terms such as "dynamic signature", "digital signature", or "biometric signature" can also be found, with the last term "biometric signature" probably resonating the most with the public. In foreign publications, we use the English term "digitally captured signature" and the abbreviation "DCS". However, in professional literature, other terms can also be encountered, such as "digital signature" or "electronic signature", which, similar to their Slovak equivalents, represent more general terms referring also to objects that are not manually made.

Since when has the CEI of the Police been dealing with the topic and examination of DVP?

At the Department of Graphology and Linguistic Expertise of the Criminalistic and Expertise Institute of the Police (CEI), we began to address this topic at the end of 2012. Even then, DVPs were used for electronic document signing, especially in banks, and biometry and biometric signatures became a major topic at technological conferences. Thanks to acquired contacts, as well as international and domestic projects, since then, we have been doing everything in our power at CEI to ensure optimal graphological examination of DVP. This process does not end here, as the technological development of this examination object continues.

Does this topic also feature abroad? Do you address it in collaboration with other countries?

CEI is part of the European network of forensic institutes ENFSI. We belong to the working group dedicated to the forensic examination of handwriting (ENFHEX), which closely collaborates with experts from overseas, such as from the USA, Australia, Canada, New Zealand, and other countries. The topic of examining DVP has so far been the subject of two international projects in which our department participates. Even outside of these projects, our institute operates in a highly interactive and intensive collaboration with colleagues and laboratories from around the world.

What position does CEI hold in Slovakia and abroad regarding knowledge, experience, and readiness for examining cases involving DVP?

Unique in Slovakia, significant abroad. In the history of addressing this topic, we have not only focused narrowly on the possibilities and conditions for optimal examination of DVP but also tried to grasp the topic globally. We started with defining DVP, the understanding of which affects the security aspects of its use as well as the specificity of its graphological examination. We addressed DVP from the perspective of biometrics, legislation, security of use by user companies, or usage contexts, and most importantly, we have developed procedures for optimal examination of DVP.

When did you have the first case of DVP discrepancy and how did it turn out?

We addressed the first case at the beginning of 2017, and we managed to prove that they were not genuine signatures of the declared writer.

How many cases of DVP falsification do you handle annually?

Without specifying numbers, it is necessary to distinguish between the number of cases involving DVP that we consult annually and the number of cases that actually come to us for examination. We consult several cases annually, but only a small number comes to us for examination due to various reasons that we cannot influence. However, it is increasingly common for cases to involve dozens of individuals, whose signature authenticity needs to be verified.

You can read the second part of the interview in a future blog. You will learn about the difference between DVP and a traditional signature, as well as how digital signatures are professionally examined.