What is electronic signature? Complete Guide 2026

An electronic signature is a set of data in electronic form, which are joined or logically associated with other data in electronic form at which signer uses to sign. This definition, from eIDAS regulation (regulation (EU) n°910/2014), covers wide spectrum ng technical mechanisms, from simplest (check box, type name) to most sophisticated (qualified cryptographic certificate).

In French law, article 1367 ng Civil Code states that "signature necessary for perfection ng legal act identifies who aposes it" at that, when electronic, it "consists in use ng reliable identification process guaranteeing its link sa document it attaches to". Process reliability is presumed for signatures qualified under eIDAS.

Practically, an electronic signature fulfills three functions: it identifies the signatory, it expresses his consent to the content of the document, and it guarantees the integrity of the document (any modification after signing is detectable).

The mechanism is based on two pillars: l'authentication of the signer and l'integrity of the document.

To authenticate signer, one uses one or more identification factors: trusted email address (single-use link), OTP code received via SMS, personal cryptographic certificate, etc. To guarantee integrity, one calculates fingerprint (hash) ng document at moment ng signature. If document is modified afterward, fingerprint no longer matches — signature is then invalidated.

In solutions like Certyneo, the process relies on PDF processing libraries that integrate these cryptographic metadata directly into the file. A timestamped audit trail (action log) completes the system by recording each step: sending, opening, OTP validated, signature, etc.

On the technical side, several security mechanisms strengthen the inviolability of the process: qualified timestamping (RFC 3161) applies certified time proof to each signature; TLS 1.3 encryption protects data in transit; geolocation and the signatory's IP address are recorded for traceability; finally, in certain flows (AES/QES), behavioral biometric data (typing speed, pressure) supplement the identity fingerprint.

The concept of non-repudiation is central: thanks to the timestamped and cryptographically signed audit trail, it is technically impossible for a signatory to deny having signed a document without falsifying the chain of evidence. In terms of archiving, French regulations (decree 2016-1673) require 10-year retention for most commercial acts — Certyneo ensures this archiving with probative value in sovereign hosting (EU).

In France, electronic signature ay recognized since law n°2000-230 ng March 13, 2000, which modified Civil Code to consecrate electronic writing at electronic signature as equivalent sa their paper counterparts. Article 1366 specifies that electronic writing "has same probative force as writing on paper support".

At European level, eIDAS regulation (EU) n°910/2014 creates unified legal framework for electronic signatures. Its article 25 establishes non-discrimination principle: "it cannot be refused to electronic signature its legal effects at admissibility as evidence in court solely because this signature presents itself in electronic form". Qualified signatures (QES) also benefit from legal presumption equivalent sa handwritten signature in 27 Member States.

For common documents (commercial contracts, work contracts, quotes, NDA, mandates), an advanced signature (AES) offers excellent balance between ease of use at legal security. Qualified signature (QES) is reserved for very high value acts o situations where sectoral regulation explicitly requires it.