FIELD: physics, computer engineering.
SUBSTANCE: invention relates to computer engineering. A decoding device for decoding encoded audio/video content, comprising a decoder and a security module, having an internal setting and realises the following operations: obtaining at least a first set of at least two control words; selecting one of at least said two control words based on at least a first part of the internal setting; transmitting the selected control word to the decoder, obtaining an additional set of at least two control words; additional selection of one of at least two control words of the additional set based on at least a second part of the internal setting; and transmitting the additional selected control word to the decoder; wherein decoder comprises at least a decoding module for decoding the encoded audio/video content, and means of realising at least a first cryptographic function (H), which convert the selected control word to a first final control word and converts the additionally selected control word to an additional final control word, the decoder also comprises means of decoding at least part of the encoded audio/video content using the final control word and at least the additional part of the encoded audio/video content using the additional final control word.
EFFECT: efficient protection of transmitted content.
9 cl, 2 dwg
