From the Cesar’s cipher to our days, the cryptography has always had the final aim to guaranty the secrecy in communication and information transfer. In the Second World War it became quite necessary, and determined strategies that changed the course itself of events, as it is well known. Nevertheless only in the last decennia the public administrations have been oriented to the use of cryptographic forms under the pressure of the Technological Integration. More and more complex but regularly disclosed algorithms have been studied, that follow the "irreversible" mathematic processes. In our country, the act 675/96 (known as "legge Bassanini") concerns protection of personal data. Organizations like AIPA (Autorità per l’Informatica nella Pubblica Amministrazione) think of projects finalized to the study and realization of softwares and hardwares in order to guaranty safe cryptographic procedures oriented to the relationship user/public administrations in the formal act of the signature: therefore a passage between traditional signature and digital signature. From a sociological point of view, an aspect - latent at the moment, linked to the undetermined proprieties of the digital identity - will have to be soon considered.