a technique to manage members of a group of decoders having access to broadcast data , each group member sharing a common broadcast encryption scheme comprising the steps of , in a stage for a decoder to become a group member , receiving keys pertaining to the position in the group according to the bes , receiving a current group access data comprising a current group access key , and in a stage of accessing broadcast data , using the current group access data to access the broadcast data , and in a stage of renewing the current group access key , sending a first group message comprising at lease a next group access key encrypted so that only non - revoked decoders can access it , said group message being further encrypted by the current group access key , updating the current group access key with the next group access key .