Digital signatures: types and verification

Electronic signatures are a key tool in today’s digital business world. They allow businesses and individuals to sign contracts and documents quickly, securely, and in a legally binding way—completely online. However, whether an electronic signature is actually legally valid is crucial. Not all types of signatures have the same legal status, and it’s important to know how to verify the authenticity and validity of an electronic signature.

In this guide, you will learn:

• The different types of electronic signatures and their legal significance.
• How to verify if an electronic signature is valid.
• Which tools can help you check signatures.

From simple to qualified: the different types of electronic signatures:

The legal framework for electronic signatures varies by country, but generally, there are three types of electronic signatures:

1. Simple electronic signature (SES)

A simple electronic signature consists of data in electronic form that is linked to other data and used as a signature. This type offers the least security and is hardly enforceable in a legal sense. Examples include:

• scanned handwritten signatures on PDF documents
• email signatures
• the default signature in almost all PDF/signature solutions.

2. Advanced electronic signature (AES)

An advanced electronic signature uses encryption to ensure that the signer's identity can be clearly verified and that the document's integrity is preserved. The AES theoretically offers more security than a simple signature. However, the legal situation is ambiguous, and a court typically decides on its evidentiary value. Read more in this blogpost "Are electronic signatures valid in Switzerland?"

3. Qualified Electronic Signature (QES)

The qualified electronic signature represents the highest security level. It requires a signature certificate issued by a certified trust service provider. In Switzerland and the EU, only the QES is legally equivalent to a handwritten signature

Why is verifying electronic signatures important?

A digital signature is not always immediately recognizable as legally valid. For example, a signature inserted into a document may visually appear to be valid, but only a technical verification can confirm whether the document is actually legally signed. When verifying, key things to look for are:

• Is the signature linked to the identity of the signer?
• Has the document remained unchanged since it was signed?
• In which legal jurisdiction (Switzerland or the EU) is the signature valid?
• How do I verify a qualified electronic signature (QES)?

How do I verify a qualified electronic signature (QES)?

To determine if a qualified electronic signature (QES) is valid, several steps need to be followed. The signature certificate is crucial, as it establishes the connection between the signer and the encrypted information. The certificate provides information such as:

• the identity of the signer
• the time of signing
• the signature level and legal jurisdiction
• any subsequent changes to the document.

Step-by-step guide to verifying a QES

1. Open the document and access signature information: Many PDF viewers offer the option to directly display signature details.
2. Check the signature certificate: Verify if the certificate was issued by a recognized trust service provider.
3. Use validation tools: Use official validation services to confirm the signature's validity. Different tools are available depending on the legal jurisdiction:

Validation tools: A look at the best services

In Switzerland
The Swiss Federal Administration offers an online validator service that can be used to check signatures. The service provides both brief reports and detailed information about the signature and its certificate.

Validation report for a valid QES. The warning message appears because the identity of the certificate holder is not explicitly stated, but a pseudonym has been used.

In the EU
The RTR Signature Verification Service is a well-known platform for verifying signatures within the EU. It provides comprehensive information on the legal validity of an electronic signature.

Other Tools
Since April 2024, the eIDAS Validator by Digital Europe, specifically designed for validation in the EU, has also been available as a demo version.

Frequently asked questions (FAQ)

1. What is the difference between an advanced and a qualified electronic signature?
The qualified electronic signature (QES) is legally equivalent to a handwritten signature due to additional security standards and a signature certificate from a recognized provider.

2. How long is a qualified electronic signature valid?
A QES can still be validated years after the certificate expires if it is LTV-enabled (Long Term Validation).

3. Is an electronic signature legally valid in every country?
The legal validity depends on the jurisdiction and the type of signature. In Switzerland and the EU, only the qualified electronic signature is equivalent to a handwritten signature.

Conclusion: legally compliant electronic signatures in the digital world

Electronic signatures are essential for the digitization of business processes. However, to ensure that a document is truly legally valid, a simple visual check is not enough. Proper verification includes checking the signature certificate, signature level, and legal jurisdiction. Only qualified electronic signatures provide the necessary legal certainty in Switzerland and the EU.

Trust certified providers and let us help you optimize the security of your digital business processes. Feel free to reach out—we're here to help you make your signatures legally compliant and future-proof. Or are you interested in creating a QES right now?