Example embodiments relate to exchanging data between several computers or multimedia units through a public network while guaranteeing at the same time the confidentiality of these data. Specifically, the creation and use of a virtual private network (VPN) is disclosed. The virtual private network (VPN) may have a plurality of units connected to a public network, each unit having a security device which may have a unique number UA1. The method may include generating a right Dn associated to the unique number UAn, by the security device of a unit Un, transferring the right Dn to the security device of at least one second unit Um, encrypting the data sent by unit Un and the description of the Dn right by a encryption data key KS, and receiving the encrypted data by the second unit Um, wherein the encrypted data is presented to the security device of the second unit Um to verify if the right Dn is present, and if the right Dn is present, then decrypting the data by the encryption data key KS.