FAQ
What is a qualified electronic signature (QES)?
A qualified electronic signature (QES) is the most secure type of electronic signature under EU law. It is:
- Based on a qualified certificate issued by a Qualified Trust Service Provider (QTSP),
- Created with a qualified signature creation device,
- Legally recognised as the same as a handwritten signature in all EU Member States.
This means a QES gives the highest level of assurance about who signed and that the document has not been changed since signing.
What is a qualified electronic seal (QESeal)?
A qualified electronic seal is like a company’s digital stamp. Instead of a person, it is applied by an organisation (such as a business, government body, or hospital).
It proves two things:
- Origin: the data really comes from that organisation,
- Integrity: the data has not been changed.
When qualified, the seal has an EU-wide legal presumption of correctness, meaning it is automatically trusted in courts and by regulators.
What is the difference between a signature and a seal?
- A signature is made by a natural person and shows that a specific individual approved or signed a document.
- A seal is applied by a legal person (an organisation) and proves that the data really came from that organisation and is unchanged.
Think of a signature as personal approval, and a seal as an official stamp from an organisation.
What is a trust service and what is a Qualified Trust Service Provider (QTSP)?
A trust service is a regulated electronic service that helps create trust in the digital world. Examples are electronic signatures, electronic seals, time stamps, website certificates, and preservation of signatures and seals.
A Qualified Trust Service Provider (QTSP) is a company that has been audited and officially listed on the EU Trusted List. Only QTSPs can deliver “qualified” trust services, which enjoy legal recognition across the EU.
Why can a signature that was valid at signing fail years later?
Electronic signatures rely on certificates and algorithms. These have a limited life.
- Certificates can expire or be revoked,
- Security standards and algorithms become outdated,
- Validation servers may no longer exist.
So a signature that was valid in 2024 may appear “unverifiable” in 2034 unless it is preserved with additional evidence.
How do you keep a signature or seal verifiable long-term?
This is done through a process called Qualified Preservation:
- Ingest & validate: the signature or seal is checked, and a signed validation report is created.
- Build evidence: additional proof (Evidence Record Syntax + qualified time stamps) is added without touching the original file.
- Renew evidence: over time, new time stamps are added to keep the proof strong even as technology changes.
This ensures that signatures and seals remain legally verifiable for decades.
Where can I verify if a provider or service is truly “qualified”?
Use the official EU Trusted List Browser (sometimes called the eIDAS Dashboard): https://eidas.ec.europa.eu/efda/trust-services/browse/eidas/tls
- Select your country,
- Check the list of Qualified Trust Service Providers (QTSPs),
- See which qualified services they are authorised to provide.
If a provider is not on the list, it is not qualified.
What is an advanced electronic signature (AdES)?
An advanced electronic signature (AdES) is more secure than a simple e-signature. It must meet four conditions under eIDAS:
- It is uniquely linked to the signer,
- It can identify the signer,
- It is created using data under the signer’s sole control,
- It is linked to the signed data so any later changes can be detected.
An AdES is not always legally equivalent to a handwritten signature, but it offers a higher assurance level than a basic e-signature.
What is an advanced electronic seal (AdESeal)?
An advanced electronic seal is the organisational equivalent of an AdES. It must:
- Be uniquely linked to the sealing organisation,
- Identify that organisation,
- Be created under its sole control,
- Show if the data has been altered after sealing.
It’s like a digital company stamp with added security and tamper-evidence.
Why can a valid signature stop validating over time?
Signatures depend on certificates and cryptographic standards. Certificates eventually expire or are revoked (for example if the person signing reported their eID lost), and algorithms become outdated. Validation services like OCSP (Online Certificate Status Protocol) responders may also go offline. Without added preservation evidence, a document that was once valid may later appear unverifiable.
Is PAdES LTV enough, or do I still need preservation?
PAdES LTV (Long-Term Validation in PDF) embeds extra data in the document so the signature can be checked later. However, it does not refresh or renew evidence as technology changes.
- PAdES LTV = document-level proof, useful in the short to medium term.
- Qualified Preservation = service-level renewal and independent evidence, ensuring validity for decades.
For critical records, both are recommended.
How does preservation help when security standards get outdated?
Cryptographic algorithms age, and what is secure today may not be secure in 10 years. Preservation adds new qualified timestamps and evidence records at intervals, refreshing trust so the evidence remains valid even if older algorithms become unsafe.
Who supervises qualified trust services in Belgium?
The FPS Economy (Federal Public Service) is the supervisory authority for trust services. They maintain the Belgian Trusted List and oversee the certification of QeA providers.
Where can I read the exact legal text?
You can find the full rules in the eIDAS Regulation:
- Article 34 – Qualified Preservation of Signatures,
- Article 40 – Validation and Preservation of Seals,
The text is available on EUR-Lex.