The electronic signature or digital signature is a device that guarantees the totality of an electronic file and certifies its author in comparison with the handwritten seal on a paper document. It coincides with a sequence of characters, but by the fact that it is not visual, it is different from the written signature.
Since the implementation of the law n° 2000-230 of March 13, 2000, the e-signature has a legal value. It shows that the electronic signature commits the agreement of the signatory identical to the handwritten signature. Subject to the use of a credible identification process that guarantees its relationship with the act to which it is attached, Article 1316-4 of the Civil Code states that the digital signature forms a certificate that is as valid as a handwritten signature. The attestation of reliability of the process can take various aspects according to the type of electronic signature (qualified signature, advanced signature, simple signature).
First, there is the implementation of a legal electronic signature architecture. For this, one chooses between a hash function and an asymmetric encryption. A public key and a private key will be generated once the encryption is chosen. The public key and the hash function will be transmitted through an unsecured channel to the recipient, but the private key must be secret. Then, there is the preparation of the signed message. So, we produce a condensate of the message by the chosen hash function, we encrypt the condensate thanks to the encryption function by using its private key, then, the result obtained is the signature of the message. Then we accommodate the signed message by putting the message in the clear and the signature in an arbitrary frame. Now all that remains is to send the signed message over an unsecured channel. During the reception of the message, the recipient has to check the authenticity of the message and sets up a protection against attacks.
Functions of the signature
The following properties must be presented in a mechanism of digital signature or e-signature: it must assure that the file has not been modified between the moment when the author signed it and the moment when the reader consults it (integrity use), it must present a file that allows to identify the organization or the person that applied his signature to the reader (identification use) The following formalities must be assembled for this: irrevocable, unalterable, not reusable, unforgeable and authentic. The importance of the soft digital signature values is based on asymmetric cryptography.