What is a Qualified Electronic Signature?

A Qualified Electronic Signature is an Advanced Electronic Signature based on a qualified certificate. It is created by a Qualified Electronic Signature Creation Device (QSCD).

The Qualified Electronic Signature (QES) includes all the secure features that an Advanced Electronic Signature (AdES) provides by:

- Having the ability to uniquely identify and link its signatory to the electronic signature.
- Allowing the signatory to have sole control of the keys used to create the electronic signature.
- Identifying if the data has been tampered with after its accompanying message has been signed.
- Invalidating the signature if signed data has been altered in any manner.

Simply put, the difference between the AdES and the QES is the addition of a qualified certificate. This certificate is issued by a qualified trust service provider, and it attests to the authenticity of the electronic signature to serve as proof of the identity of the signatory.

However, there is more to creating the QES than just the addition of the qualified certificate to an AdES. The signature itself must be created using a Qualified Signature Creation Device (QSCD). This device is responsible for qualifying a digital signature with specific software and hardware that ensures that:

- Only the signatory has control of their private key
- The signature creation data that is generated is managed by a qualified trust provider
- The signature creation data is unique, confidential and protected from forgery.

Under eIDAS regulations, a QES has the same legal effect as a handwritten signature. It is recognized in all member states of the EU.

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