This invention concerns a system and a method of transmission and storage of audio/video data in encrypted form between a distribution centre and at least one exploitation module.Instead of transmitting the information allowing the decryption in parallel to said data, these information are regrouped in a decryption data file comprising equally the data that define the access conditions to said audio/video data. This file is stored independently from said data and can be used for either an immediate use or a deferred one.