BLUE DIGITAL SIGNATURE

The digital signature is a mechanism making it possible to guarantee the integrity of an electronic document and to authenticate its author, by analogy with the handwritten signature of a paper document.

A digital signature mechanism must have the following properties:

It must allow the reader of a document to identify the person or body that has affixed his signature (identification property).
It must guarantee that the document has not been altered between the time the author signed it and the time the reader consults it (integrity property).

For this, the following conditions must be met :

• authentic: the identity of the signatory must be able to be traced with certainty;
  
• forgery-proof: the signature cannot be forged. Someone cannot pass themselves off as another;
  
• non-reusable: the signature is not reusable. It is part of the signed document and cannot be moved to another document;
  
• unalterable: a signed document is unalterable. Once it is signed, it cannot be modified any more;
• irrevocable: the person who signed cannot deny it.

In practice, most of the existing digital signature procedures rely on asymmetric cryptography