Individual writing characteristics provide greater security in the digital signing process
A biometric signature combines the traditional handwritten signature with the benefits of digital signatures. Unlike a simple electronic signature, it captures not only the visible image of the signature but also individual characteristics of the signing process. These include writing speed, writing direction, writing pressure and pauses. These additional pieces of information make it easier to trace the signing process in the event of a dispute and enhance the evidential value of an electronic signature. Companies can therefore benefit from fully digital processes without having to give up the familiar experience of signing by hand.
This article explains the characteristics of a biometric signature, its legal classification and how it is implemented technically.
Table of contents
Key facts at a glance
- In addition to the visual appearance of the signature, a biometric signature captures individual writing characteristics such as speed, writing direction, pressure and pauses.
- A biometric signature can be used as an advanced electronic signature (AES) if the requirements of the eIDAS Regulation are met.
- Under the GDPR, biometric data may fall into the category of special categories of personal data and are therefore subject to enhanced data protection requirements.
- Biometric data are of a particularly sensitive nature and should be embedded in the document in encrypted form.
What is a biometric signature?
A biometric signature does not only capture the visible appearance of the signature but also records the course of the signing process. The biometric data captured can be used to verify authorship in the event of a dispute, thereby increasing the traceability of an electronic signature.
The signature is usually carried out on a smartphone, tablet or signature pad. The signature software records all transactional data during the signing process and stores it in encrypted form within the document.
A biometric signature can be used as an advanced electronic signature (AES) under the eIDAS Regulation if the relevant requirements are met. It is suitable for the vast majority of business documents and enables fully digital signing processes without, in most cases, requiring prior identification as is the case with a qualified electronic signature.
Please note: Whether an advanced electronic signature is sufficient or a qualified electronic signature (QES) is required always depends on the statutory formal requirements applicable to the respective document.
Which biometric characteristics are captured?
Biometric characteristics are individual physical or behavioural traits used to identify or verify a person. The best-known examples are fingerprints, the iris, facial features or voice. Well-known examples include fingerprints, the iris, facial geometry and the voice.
The process of handwriting also contains individual biometric characteristics. Although the appearance of a signature may vary, the motions during signing follow individual characteristic patterns. These are precisely the individual characteristics captured by a biometric signature.
Depending on the hardware and signature software used, the following data may be recorded:
- Writing speed
- Writing direction
- Pauses while writing
- Duration of the signature
- Position of individual movements
- Pressure applied to the input device
Unlike methods such as fingerprint or facial recognition, however, a biometric signature is not used to authenticate access to a system. Its purpose is to increase the evidential value of the signature and to establish a link between the signature and the signatory in the event of a dispute.
Benefits of biometric signatures for companies
Particularly in industries with a high volume of documents, biometric signatures help speed up processes while ensuring transparent and traceable documentation.
Key benefits include:
- High acceptance: Employees, customers and business partners sign by hand on any tablet, smartphone or signature pad.
- End-to-end digitalisation: Documents can be signed digitally, processed further and archived without media discontinuity.
- Greater evidential value: The additional biometric characteristics captured can be used to verify authorship in the event of a dispute.
- Faster processes: Contracts, delivery notes, handover records and HR documents can be signed immediately on site or while on the move.
- Lower costs: There are virtually no costs for paper, printing, postage and physical archiving.
- An authentic signing experience: The signature looks and feels like a traditional signature on paper. This builds trust among business partners who have little experience with digital processes.
Biometric signatures and the GDPR
Under the GDPR, biometric data fall under the special categories of personal data and are subject to enhanced data protection requirements. This is particularly the case when they are processed for the purpose of uniquely identifying a natural person. For companies, this entails enhanced requirements with regard to transparency, purpose limitation and data security.
Companies using biometric signatures should pay particular attention to the following:
- The processing requires an appropriate legal basis.
- The data may only be used for the intended purpose.
- Biometric information must be effectively protected against unauthorised access.
- Data subjects must be informed transparently about how their data is processed.
In addition to the legal requirements, technical implementation also plays a key role. What matters is not only the encryption of biometric data, but also its secure storage and controlled access when required.
Evidential value of the signature
The biometric signature’s evidential value results from a combination of visual signature image and additionally captured biometric characteristics.Specialised analysis software can be used to make the stored biometric data visible retrospectively and examine it in detail. The process is comparable to watching a video in slow motion, allowing individual sections of the signature to be examined closely.
Variations between individual signatures by the same person do not limit their evidential value. The authenticity of a signature can be assessed based on the biometric data as a whole, even if individual details of the electronic signature do not exactly match a previous signature. A handwriting expert can use this data to provide a well-founded assessment of the authorship of the signature.
How does a biometric signature work with inSign?
The technical implementation of a biometric signature varies depending on the signature solution used. The example of inSign shows how biometric characteristics are captured and protected.
As a provider of an electronic signature solution, inSign supports various digital signing methods, including handwriting (advanced electronic signature in accordance with the eIDAS Regulation). When creating a handwritten electronic signature, inSign captures not only the visible signature image but also biometric characteristics of the handwriting in compliance with data protection requirements, such as writing speed, writing direction, writing pressure and pauses. These values are embedded in the PDF document using asymmetric encryption. The private key required for decryption can be stored with an independent third party, such as a notary. This ensures that no unauthorised person can access the biometric data.
Try it now and sign by hand:
Conclusion: Legally compliant and traceable
A biometric signature combines the familiar experience of a handwritten signature with the requirements of a legally compliant digital signing process. Capturing individual writing characteristics creates a robust data record that can be analysed and attributed to a person in the event of a dispute. At the same time, biometric data is subject to strict data protection requirements under the GDPR. Encryption, purpose limitation and the involvement of independent third parties are therefore key elements of a legally compliant implementation.
FAQ: Frequently asked questions about biometric signatures
A simple electronic signature generally only stores the visual image of the signature. A biometric signature additionally captures dynamic writing characteristics such as speed, direction and pauses, significantly increasing its evidential value.
The processing of biometric data when signing is possible if the requirements of Article 9 of the GDPR are met. These include clear purpose limitation, end-to-end encryption and access restricted to an independent, trusted third party.
In addition to the signature image, dynamic characteristics of the writing process are captured, such as speed, direction, pressure and pauses in movement. These values are embedded in the respective document in encrypted form.
Yes. It can be used as an advanced electronic signature if it meets the requirements of the eIDAS Regulation and is therefore legally binding in most business contexts.
Variations are normal and do not affect its evidential value. The authenticity of the signature can still be established based on the biometric data as a whole.
About the author
Mirko Röder
As Product Owner at inSign, I have been responsible for our signature solution for many years. IT is my passion and has fascinated me ever since I was a child. I have known inSign since its inception and have since gained a great deal of experience in the field of digital signatures, which I am happy to share.
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