What is an electronic signature and how does it work?

Definition

What an electronic signature is under the law

The EU eIDAS Regulation (EU 910/2014) defines an electronic signature as data in electronic form which is attached to or logically associated with other data in electronic form and which is used by the signatory to sign (Art. 3(10)).

In other words: it is whatever, in a digital document, shows that a person has signed it. In Spain, Law 6/2020 (Ley 6/2020), in force since 13/11/2020, regulates electronic trust services and complements the eIDAS Regulation. It repealed the previous electronic signature law, Law 59/2003 (Ley 59/2003).

What the law says

Types of electronic signature and their value

The eIDAS Regulation distinguishes three types of electronic signature, from fewer to more requirements. Only the highest level, based on a qualified certificate, has by law the same legal effect as a handwritten signature (Art. 25(2)).

For all the others, the Regulation says they cannot be denied legal effect or value as evidence in court solely because they are electronic (Art. 25(1)). What matters, then, is being able to prove the signature.

The proof

What makes an electronic signature stand as evidence

If someone challenges an electronically signed document, the signature has to be proved (Spanish Civil Procedure Act, Art. 326). That is what the evidence recorded at signing is for:

• The document’s digital fingerprint before and after signing: any later change is detected.
• Date and time of each step: sending, opening and signing.
• The IP address and device used to sign.
• How the signer was identified: their one-time code by email or SMS.

Every signed document carries a qualified timestamp, issued by a provider on the Spanish Ministry’s trusted list. More details in the legal validity of electronic signatures.