A method for multimedia transmission, comprising: generating a copy of a multimedia stream to render first and second clear streams having identical predetermined portions; determining locations of the predetermined portions at least in one of the streams using corresponding offsets from at least one packet identifier, PID; storing the offsets in a critical packet offset table ; sending the first clear stream to a first conditional access, CA, component to encrypt the entire first clear stream to render a completely encrypted first stream ; obtaining a first encrypted version of the predetermined portions from the completely encrypted first stream based on the determined locations of the predetermined portions; using the determined locations of the predetermined portions in the second clear stream from the critical packet offset table, to encrypt the predetermined portions using a second CA component leaving the remaining portions of the second clear stream unencrypted to render a partially encrypted second stream including a second encrypted version of the predetermined portions; and inserting the first encrypted version of the predetermined portions, obtained from the completely encrypted first stream using the critical packet offset table, into the partially encrypted second stream for transmission thereof adjacent to the second encrypted versions of the predetermined portions identified by the offsets stored in the critical packet table, the offsets being used for identifying the locations of the encrypted predetermined portions in the completely encrypted first stream for obtaining them and inserting them into the partially encrypted second stream. generating a copy of a multimedia stream to render first and second clear streams having identical predetermined portions; determining locations of the predetermined portions at least in one of the streams using corresponding offsets from at least one packet identifier, PID; storing the offsets in a critical packet offset table ; sending the first clear stream to a first conditional access, CA, component to encrypt the entire first clear stream to render a completely encrypted first stream ; obtaining a first encrypted version of the predetermined portions from the completely encrypted first stream based on the determined locations of the predetermined portions; using the determined locations of the predetermined portions in the second clear stream from the critical packet offset table, to encrypt the predetermined portions using a second CA component leaving the remaining portions of the second clear stream unencrypted to render a partially encrypted second stream including a second encrypted version of the predetermined portions; and inserting the first encrypted version of the predetermined portions, obtained from the completely encrypted first stream using the critical packet offset table, into the partially encrypted second stream for transmission thereof adjacent to the second encrypted versions of the predetermined portions identified by the offsets stored in the critical packet table, the offsets being used for identifying the locations of the encrypted predetermined portions in the completely encrypted first stream for obtaining them and inserting them into the partially encrypted second stream. <EOS>