An electronic signature is a 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, where the signatory is a natural person.

Like its handwritten counterpart in the offline world, an electronic signature can be used, for instance, to electronically indicate that the signatory has written the document, agreed with the content of the document, or that the signatory was present as a witness.

In case you want to seal a document as a legal person (e.g. as a business or organisation), you might be instead interested in an electronic seal.

An electronic seal is data in electronic form, which is attached to or logically associated with other data in electronic form to ensure the latter’s origin and integrity, where the creator of a seal is a legal person (unlike the electronic signature that is issued by a natural person).

In this purpose, electronic seals might serve as evidence that an electronic document was issued by a legal person, ensuring certainty of the document’s origin and integrity. Nevertheless, across the European Union, when a transaction requires a qualified electronic seal from a legal person, a qualified electronic signature from the authorised representative of the legal person is equally acceptable.

An ‘electronic signature’ is a legal concept that is defined in eIDAS by the following:

“‘electronic signature’ means 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;” (eIDAS Article 3.10)

A digital signature, on the other hand, refers to a mathematical and cryptographic concept that is widely used to provide concrete and practical instances of electronic signature. The definition given by ETSI TR 119 100 is that of data appended to, or a cryptographic transformation of a data unit that allows a recipient of the data unit to prove the source and integrity of the data unit and protect against forgery e.g. by the recipient.

These two concepts should be distinguished, as all electronic signatures are not necessarily digital signatures.

The eIDAS Regulation defines three levels of electronic signature: 'simple' electronic signature, advanced electronic signature and qualified electronic signature. The requirements of each level are built on the requirements of the level below it, such that a qualified electronic signature meets the most requirements and a 'simple' electronic signature the least.