Patent ID: 8488795

Claim:
A method to encrypt media data between user equipment and provider equipment, comprising: providing, to the user equipment and the provider equipment, a first symmetric key used in a protection mechanism of a network protocol of a control layer based on symmetric keys to establish a communication session between the user equipment and the provider equipment; providing a first time-variable parameter by the provider equipment; transmitting the first time-variable parameter from the provider equipment to the user equipment; computing, by the provider equipment, a second symmetric key for protection of the key-management protocol, using a predefined function depending on at least the first symmetric key and the first time-variable parameter; and computing, by the user equipment, the second symmetric key based on the predefined function depending on at least the first symmetric key and the first time-variable parameter transmitted from the provider equipment; encrypting, by the user equipment or provider equipment, the media data depending on the second symmetric key to produce encrypted media data; transmitting the encrypted media data without requiring establishing of said communication session; receiving the encrypted media data by the provider equipment or user equipment; and decrypting, by the provider equipment or the user equipment, the encrypted media data using the second symmetric key provided, and where a third time-variable parameter is respectively derived by the user equipment and the provider equipment from the first time-variable parameter depending on which the second symmetrical key is computed respectively by the user equipment and the provider equipment.