From a cryptographic point of view, an electronic signature is understood as a set of partial cryptographic functions that ensure identification, authentication, integrity, and undeniability. Mathematically, the electronic signature is just one large number.
The following figure shows the process of creating a secured electronic signature. The numbers in the figure indicate the steps of the process of creating a guaranteed electronic signature.
Any digital data such as text (PDF, TXT, DOCX, RTF, XLSX, ...), image (BMP, JPG, GIF, PNG, ...), audio (WAV, MP3, FLAC, (AVI, MPG, ...), executable files (EXE, COM, ...), and more, can be signed electronically. Essentially, anything can be signed electronically.
The following figure shows the process of verifying the guaranteed electronic signature. The numbers in the figure indicate the steps of the verification process of the guaranteed electronic signature.
The secured electronic signature ensures integrity of the messages and documents transmitted, identification of the communicating parties, authentication of the communicating parties (i.e. verification of their identification), undeniability and unrefusability.
However, the guaranteed electronic signature does not guarantee the legal acceptability of the signed documents.
The eIDAS Regulation defines the guaranteed electronic signature in Article 3 (11), if it fulfills the conditions in Article 26, then: