La gestion des DRM en perspective

2- cryptology with asymmetrical key

The principle of cryptography by private/public key lies in the existence of a couple of keys for each interlocutor. These two keys, one private and the other public one, are generated at the same time and are closely dependant. The private key is personal and does not have to be revealed with which that is. Conversely, the public key can be accessible to no matter whom, for example directly on the network. The principle of use is as follows : an encrypted message with a public key is décryptable only by the corresponding private key. Conversely, an encrypted message with a private key can be deciphered only by its public key.^7(*)

This system is often used in relation to mechanisms of authentification and electronic signature. It is besides this one which was « adoptee » by the 13 the Mars law 2000 which transposed the directive on the electronic signature from December 13, 1999.^8(*) Nevertheless, this type of coding is generally rather slow. Also, « one frequently uses the system of «the numerical envelope»: the message is transmitted quantified with a random symmetrical key «M», and the key «M» is transmitted quantified with the public key of the recipient ». ^9(*)

* ⁷ The asymmetrical algorithm most known is the RSA.

* ⁸ In this respect, article 1316 of the Civil code gives a definition of the writing  : «  The literal proof, or written proof, results from a continuation from letters, natures, figures or of all other signs or symbols equipped with an understandable significance, whatever their support and their methods of transmission  ». Article 1316-4 continues, in particular, on the electronic signature  : «  the signature necessary to the perfection of a legal document identifies that which affixes it. It expresses the assent of the parts to the obligations which rise from this act. When it is affixed by a public officer, it confers the authenticity on the act. When it is electronic, it consists of the use of a reliable process of identification guaranteeing its bond with the act to which it sticks. The reliability of this process is supposed, until contrary proof, when the electronic signature are created, the assured identity of the signatory and the guaranteed integrity of the act, under conditions fixed by decree as a Council of State  ».

* ⁹ Philippe Chantepie, Technical Measurements of Protection of works & DRMS, 1ère Left: an Inventory of fixtures, January 8, 2003, p. 51.