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Forensic verification tool: how do you verify the authenticity of a signature?

by | Digital Signature

Consider the life of forensics and the daily challenges they face. Their work is intertwined with mystery and the determined pursuit of answers. Equipped with gloves and precision tools, they carry out their tasks with care and attention to detail. They collect evidence, analyse patterns, and uncover details that others might overlook. Amid the chaos of the crime scene, they seek the truth with meticulous precision. This profession demands patience, extensive knowledge, and a trained mind to piece together a puzzle that often appears unsolvable.

There is something deeply human in the need to understand what happened, to restore order where everything seems to have collapsed.

Quiet, almost anonymous work, but with conclusions that can change the course of an investigation. Although in real life, their work is not as glamorous as in the movies, it is still a profession that arouses respect and admiration and, for many, a dream they once wanted to achieve.

And while scenarios may change, this analysis and search for truth is not unique to physical analysis. It is also found in other disciplines, such as in the digital identity verification industry, where modern technology allows similar principles to be applied to ensure the authenticity and integrity of a signature in a fully digital environment.

Forensic verification tool applied to biometric signature

A forensic verification tool in the field of signature is a system designed to analyse and validate the authenticity of electronic signatures, in particular those made in a biometric way. This type of signature, which captures data such as pressure, speed, rhythm and specific movements at the moment of signing, is used to ensure the integrity and identity of the signatory in agreements, contracts and other digital documents.

The main purpose of this tool is to provide an additional layer of security and reliability in cases where the authenticity of a signature may be questioned. Handwriting experts use it to perform a detailed analysis of the biometric characteristics of the signature, such as the variation in pressure or the order in which the strokes were drawn, to determine whether the biometric signature corresponds to the alleged signatory or whether it has been altered.

The system can compare different signatures and provide a percentage probability as to whether they both belong to the same person using advanced analysis algorithms. The tool facilitates the work of the expert in these cases and ensures that digitally signed documents maintain their legal validity.

Where does it fit into the digital signature process?

Within the journey of a digital signature process, the tool has a fundamental role in post-signing stages, specifically when there is a dispute about the authenticity of the signature on a document.

When a dispute or claim arises over a biometric signature, this system comes into play in the verification or dispute resolution phase. In this regard, a handwriting expert or forensic analysis expert carries out a comprehensive study, comparing the recorded signature with other samples. Through analysis charts, automatic and manual comparisons and reconstruction of the signature process, a detailed assessment of the origin and validity of the signature can be provided.

ISO 19794-7: the standard for biometric signature capture

ISO 19794-7 is an international standard that regulates the capture and format of biometric signatures, ensuring that signature-related data is collected consistently and with high accuracy. This standard is essential in the context of forensic signature verification, as it provides a framework to ensure that signatures are analysed according to clear and globally recognised specifications.

Some of the key features of this ISO include:

  • Standard format: defines how the biometric data of a signature should be captured and stored, enabling interoperability between different systems.
  • Detailed biometric data: sets out the parameters to be recorded, such as the speed of the signature, the pressure applied and the trajectory of the strokes.
  • International compatibility: the standard is used worldwide, facilitating the validation of biometric signatures in different countries and platforms.

ISO 19794-7 establishes a standard format for the capture and storage of biometric signatures, and although its application is necessary to ensure data interoperability, the use of the forensic verification tool is not. The expert witness may choose the most appropriate methods to analyse the signatures, even if the signatures are presented in a format compliant with this standard.

Mobbsign Signature Analyzer analysis tool

Mobbsign Signature Analyzer is Mobbeel’s signature forensic verification and analysis tool.

The tool allows the uploading of existing signatures in standard format (extracted by the trusted authority from a signed contract) and the addition of new signatures collected via a mobile device. Once several signatures have been uploaded, either by import or acquired on the spot, the system presents the available information on the signatures.

For each instant of time, it is possible to know basic features such as:

  • X coordinate
  • Y coordinate
  • Pressure

Or other more advanced elements derived from the basic ones, such as:

  • Velocity in X
  • Velocity in Y
  • Acceleration in X
  • Acceleration in Y
  • Angular accelerations
  • Pressure variation
  • Number of strokes
  • Order of strokes
  • Stroke durations

The system facilitates the comparison of different signatures numerically or through graphs. To compare signatures, simply load the signatures to be analysed and then superimpose their graphs on the work area. Each signature will be represented in a different colour, which helps the visualisation and comparison of the data.

The expert can select which parameters to show or hide at any given time and can choose to view the graphs for each signature separately or to display the same parameters from both signatures overlaid on the same graph for a quicker and more intuitive comparison.

The tool also provides the user with an automatic comparison option, in which the system will analyse the signatures and give a percentage probability that both signatures belong to the same user.

3D pressure analysis

An interesting feature of MobbSign Signature Analyzer is the ability to display 3D pressure graphs. This visual representation allows us to observe in three dimensions how the pressure varies during the signature stroke, providing additional information about the signer’s behaviour. As with the other graphs, the user can compare the pressure graphs of different signatures to detect possible differences.

Reproduction of the signature stroke

In addition to the graphs, the tool allows for a playback of the signature trace in the form of a video. This facilitates the observation of the complete signature process, showing how each stroke is made in real time. The system offers controls to pause, adjust the speed or loop the signature, which is useful for detailed analysis. You can also compare the stroke playback of multiple signatures by dragging them into the workspace to view them simultaneously.

Additional signature information

If you want to perform a more complete analysis, our system provides detailed information about the signature, such as:

  • Date and time of signature
  • Device used (make, model, operating system)
  • Location of the signatory (country, latitude, longitude)
  • Metadata related to the hashing algorithm and the version of the software used.

This additional information helps to contextualise the signature and provides more details in the forensic analysis process.

The implementation of this system and its advanced features enable handwriting experts to perform advanced and professional forensic signature analysis. Furthermore, integration with international standards, such as ISO 19794-7, ensures that signatures are analysed in accordance with internationally recognised standards, increasing confidence and security in the verification process.

Feel free to contact us if you need to implement a biometric signature, including a forensic verification tool, in case of disputes regarding signed documents.

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