• comunicazione di gruppo
• crittografia
• MG-LKH
• servizi broadcast
• algoritmo rinnovo chiavi
• broadcast services
• cryptography
• group communication
• rekeying algorithm

This work deals with the issues regarding the distribution of confidential contents in a broadcast service. In particular the interest is focused on the problem of rekeying, that is the process by means of which the broadcast service renews the keys that are used to encrypt the contents. This operation is needed each time that some event, like the leaving of a user from the service, make the renewal of the keys necessary to ensure the secrecy of the contents. In the first part it is possible to find a description of the existing protocols of rekeying, with an eye to their strengths and weaknesses. In the second part instead the work shows an alternative protocol, with a theoretical study about its performance. Finally in the third part there is a description of the implementation of the rekeying algorithm, the performance evaluation made by a campaign of simulations and the comparison with the previous solutions.