| 摘要 |
A method of scrambling a stream of data includes obtaining from the stream a succession of first sequences (29,30) of blocks (P i ) of data, reversing the order of the blocks (P i ) in each of the first sequences (29,30) of blocks to form respective second sequences (31,37) of blocks of data, and encrypting the blocks in each second sequence (31,37) of blocks using a cipher (E K ) in block chaining mode, initialised with a respective initialisation vector (IV 3 , IV N ) for each second sequence (31,37) of blocks. For a succession of first sequences (29,30) of blocks included in a unit (26) of data within the stream, at least one initialisation vector (IV N ) for encrypting a second sequence (37) of blocks formed from a first sequence (30) of blocks in the unit is generated in dependence on at least one block in a preceding first sequence (29) of blocks of the unit.
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