A method for protection of a content scrambled by a content key CW transmitted encrypted by a content access key K, where the said content is supplied by a transmission system to at least one reception terminal by means of a service configured locally within the said reception terminal according to a set of properties Pi, i= 1 to N, which are known to the transmission system, each of the said properties Pi is represented by a data element x i recorded in the said transmission system and by a local data element y i which is obtained by measurement or calculation in the environment of the reception terminal and which is accessible in read-only mode in the said reception terminal in the same way as a content access key K, a method in which at transmission, said content key CW is superencrypted by a reversible function F by means of the contentaccess key K and at least a reversible superencryption function f i (x i), which is dependent on at least one of the properties Pi, i=1 to n, a method characterised in that: At transmission it comprises the steps of: - defining a non-empty subset of properties Pi to be verified, i = 1 to n, the verification of the properties Pi, i= 1 to n, is performed systematically or on a one-off basis, - superencrypting the said content key CW by applying, according to an ordered sequence of functions, to the said content key CW the reversible F and the reversible superencryption functions f i (x i) for each property Pi, i = 1 to n, of the said subset EP, - transmitting said superencrypted content key CW to the terminal, with a list of references designating the subset EP consisting of the properties Pi of the service to check, corresponding to data elements x i, i= 1 to n, used to calculate the reversible superencryption functions f i (x i), and to the data elements yi, i=1 to n, to be used by the terminal to calculate the reverse superencryption functions f i -1 (y i), and at reception, - for each property Pi belonging to the said subset EP, reading the local data element y i of the said terminal representing the said property P i, - revealing the value CW' of said content key CW by applying to the superencrypted content key, according to a sequence inverse to the ordered sequence, the reverse encryption function F -1 and the reverse superencryption functions f i -1 (y i) for each of the properties Pi of the said subset EP, i=n to 1, the content key CW is revealed only after verification of all the properties P i, i= 1 to n of said subset EP, - unscrambling the content by means of the revealed value CW' of the said content key CW. At transmission it comprises the steps of: - defining a non-empty subset of properties Pi to be verified, i = 1 to n, the verification of the properties Pi, i= 1 to n, is performed systematically or on a one-off basis, - superencrypting the said content key CW by applying, according to an ordered sequence of functions, to the said content key CW the reversible F and the reversible superencryption functions f i (x i) for each property Pi, i = 1 to n, of the said subset EP, - transmitting said superencrypted content key CW to the terminal, with a list of references designating the subset EP consisting of the properties Pi of the service to check, corresponding to data elements x i, i= 1 to n, used to calculate the reversible superencryption functions f i (x i), and to the data elements yi, i=1 to n, to be used by the terminal to calculate the reverse superencryption functions f i -1 (y i), - defining a non-empty subset of properties Pi to be verified, i = 1 to n, the verification of the properties Pi, i= 1 to n, is performed systematically or on a one-off basis, - superencrypting the said content key CW by applying, according to an ordered sequence of functions, to the said content key CW the reversible F and the reversible superencryption functions f i (x i) for each property Pi, i = 1 to n, of the said subset EP, - transmitting said superencrypted content key CW to the terminal, with a list of references designating the subset EP consisting of the properties Pi of the service to check, corresponding to data elements x i, i= 1 to n, used to calculate the reversible superencryption functions f i (x i), and to the data elements yi, i=1 to n, to be used by the terminal to calculate the reverse superencryption functions f i -1 (y i), and at reception, - for each property Pi belonging to the said subset EP, reading the local data element y i of the said terminal representing the said property P i, - revealing the value CW' of said content key CW by applying to the superencrypted content key, according to a sequence inverse to the ordered sequence, the reverse encryption function F -1 and the reverse superencryption functions f i -1 (y i) for each of the properties Pi of the said subset EP, i=n to 1, the content key CW is revealed only after verification of all the properties P i, i= 1 to n of said subset EP, - unscrambling the content by means of the revealed value CW' of the said content key CW. - for each property Pi belonging to the said subset EP, reading the local data element y i of the said terminal representing the said property P i, - revealing the value CW' of said content key CW by applying to the superencrypted content key, according to a sequence inverse to the ordered sequence, the reverse encryption function F -1 and the reverse superencryption functions f i -1 (y i) for each of the properties Pi of the said subset EP, i=n to 1, the content key CW is revealed only after verification of all the properties P i, i= 1 to n of said subset EP, - unscrambling the content by means of the revealed value CW' of the said content key CW.