| 摘要 |
The message (MEC) making it possible to deliver conditions of access (2) to a scrambled service intended for at least one user. The message (MEC) contains a first item (4, Al) consisting of a control word (Cwi) encrypted by an algorithm with key K1, a second item (5), the content (HASHK) of which makes it possible to validate and verify the content of the message (2). The content of the second item is controlled by a key Q. It contains n-1 additional items each containing the control word (Cwi) encrypted by an encryption algorithm with respective keys K2, K3, ..., Kj, ..., Kn. The message (MEC) is characterised in that it contains n additional items, the content of which consists of the key indices I(K1), ..., I(Kj), ..., I(Kn). The key index I(Kj) is associated with the key Kj (j = 1, 2, ..., n).
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