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eIDAS Compliance Guide

Understanding SES, AES and QES under the eIDAS Regulation

This guide provides an overview of the electronic signature levels defined by Regulation (EU) No 910/2014 – eIDAS and explains the key differences between them, with emphasis on the benefits of the Qualified Electronic Signature (QES) from the perspective of legal certainty, document integrity, and traceability.

1. The eIDAS Legal Framework

The eIDAS Regulation establishes the legal framework for electronic identification and trust services in the European Union. It defines three levels of electronic signatures:

  • SES
    Simple Electronic Signature (SES)
  • AES
    Advanced Electronic Signature (AES)
  • QES
    Qualified Electronic Signature (QES)

According to Article 25(1) of eIDAS, an electronic signature shall not be denied legal effect solely on the grounds that it is in electronic form.

According to Article 25(2), a qualified electronic signature shall have the equivalent legal effect of a handwritten signature in all EU member states.

2. Electronic Signature Levels

SES

SES — Simple Electronic Signature

Definition: any data in electronic form attached to or logically associated with other electronic data and used by the signatory to sign.

Typical use:

  • Internal approvals
  • Simple confirmations
  • Low-risk processes

Limitations:

  • Low level of identity assurance
  • Limited document integrity protection
  • Evidential value depends on context and audit trail
AES

AES — Advanced Electronic Signature

According to Article 26 of eIDAS, an advanced signature must:

  • Be uniquely linked to the signatory
  • Be capable of identifying the signatory
  • Be created using signature creation data under the sole control of the signatory
  • Be linked to the signed data in such a way that any subsequent change is detectable

Typical use:

  • Standard commercial contracts
  • Documents requiring integrity and traceability
  • Medium-risk processes
QES

QES — Qualified Electronic Signature

A qualified signature is an advanced signature based on:

  • A qualified certificate for electronic signatures
  • Issued by a Qualified Trust Service Provider (QTSP)
  • Typically using a Qualified Signature Creation Device (QSCD)

Legal basis: Art. 3(12), Art. 25(2), Annexes I and II of the eIDAS Regulation.

3. QES Advantages — Legal Certainty & Evidential Value

Legal equivalence with handwritten signatures

Under Article 25(2) of eIDAS, QES produces the same legal effects as a handwritten signature in all EU member states. This provides a superior level of legal certainty, especially in high-risk or strict compliance scenarios.

Document integrity (tamper-evident)

Qualified signatures use cryptographic mechanisms that bind the signature to the document content. Any subsequent modification invalidates the signature, becomes detectable upon verification, and protects the document's integrity.

Certainty of signing moment (Timestamp)

In practice, qualified signatures are often associated with a qualified timestamp (per Art. 41 eIDAS). This proves the exact moment of signing, is issued by a qualified provider, is resistant to challenge, and contributes to traceability and evidential value.

Robust signatory identification

The qualified certificate is issued following a rigorous identity verification process, in accordance with eIDAS requirements and relevant ETSI standards. This provides high assurance that the signature belongs to the correct person.

Complete audit trail

A qualified signing process typically includes: complete signing step journal, authentication methods used, signing moment, document integrity, and certificate information. The audit trail contributes to traceability, verifiability, and evidential value.

4. Quick Comparison

Characteristic
SES
AES
QES
Trust levelLowMediumHigh
Document integrityLimitedDetectableCryptographically guaranteed
Signatory identificationLimitedClearRigorously verified
Legal equivalence with handwritten signatureNoNoYes (Art. 25(2) eIDAS)
Qualified timestampOptionalOptionalFrequently used
Evidential valueContextualGoodVery high

5. When is QES Recommended?

QES is especially recommended for:

  • Documents with significant legal impact
  • Processes requiring high compliance
  • Situations where robust proof of signatory identity is needed
  • Documents that must be protected against modification
  • Scenarios where the signing moment must be proven with certainty

6. Conclusion

The eIDAS Regulation provides a clear framework for the use of electronic signatures in the European Union. Among the three levels, the Qualified Electronic Signature (QES) offers the highest degree of legal certainty, document integrity, and traceability, making it suitable for scenarios requiring a superior level of trust and compliance.

Need Assistance?

If you need support in choosing the appropriate signature level or understanding eIDAS compliance requirements, contact our support team.