How to check the validity of an electronic signature?

To find out whether a document bearing an electronic signature is valid, you first need to know what criteria are used to determine the validity of an electronic signature, then check that the solution provider has obtained certification before verifying the presence of a signature yourself.

The criteria for creating a valid electronic signature

First and foremost, you need to understand **what makes an electronic signature legally valid**. To be legally valid in the same way as a handwritten signature, a digital signature must :

Enable authentication of the signatory and the document;
Produce data tracking changes made to the document ;
Encrypt the document to make it forgery-proof;
Provide a storage space that preserves the document's integrity over time.

Only in this way does the electronic signature acquire legal validity.

Certifications held by the publishers of the electronic signature solution

Private key, public key, encryption, hashing: the computerized procedures used to validate electronic signatures are complex. Without computer skills, you won't be able to verify them yourself.

That's why every electronic signature tool publisher is subject to strict controls. The ANSSI (Agence nationale de la sécurité des systèmes d'information) issues a certificate guaranteeing that the electronic signature proposed complies with the law. Check that the software used to sign the document has this certificate.

Find out if a document has a valid electronic signature

Aside from questions of validity, it's also important to know whether the document actually includes an electronic signature. Unlike handwritten signatures, electronic signatures are invisible!

A number of free tools are available for this purpose. In particular, Adobe Reader lets you access the certificates linked to the document in just a few clicks. It's a quick way to get information: Adobe also shows you the estimated validity of the electronic signature contained in the document. But don't let this mean you don't have to go and find the information yourself: asking around is the surest way of ensuring that an electronic signature is valid.

Special case: responding to public tenders

You'll need a qualified or advanced digital signature with a qualified certificate.

To sign an electronic document with a qualified digital signature, you'll need to meet the same security criteria as above, but you'll also need a digital signature certificate. The certificate guarantees the identity of the signatory with certainty, thus offering the highest possible level of security.

You'll need to buy it from a certification authority (qualified trust service provider). The price varies between 100 and 300 euros, depending on the certificate's validity (2 to 3 years). It will take between 2 days and 1 month to obtain your certificate.