A central server in a network of a hybrid peer to peer type, receives a request from a client for obtaining a digital document, where the request contains a reference of the digital document. The server selects a peer system of the network likely to contain the digital document, and generates an access key for controlling access to the digital document by the client, where the access key is generated by an encrypting method using a private key of the central server, a current time when the encrypting method is executed and an address of the client on the network. The server then sends a message to the client, where the message has the reference of the digital document, an address of the selected peer system on the network and the generated access key.