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AssigneeBritish Telecommunications public limited company
InventorsPaul Martin SKIRROW, Eric PANOFF
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Encrypted data transmitted over a data network is decrypted in accordance with a cipher decryption process using a Control Word transmitted with the data. The process is arranged to automatically identify the mode by which the data has been encrypted by identifying (66) the length of the Control Word transmitted with the encrypted data. The Control Word length may be identified (64) from metadata explicitly stating the length, or by analysis of the message in which the Control Word is conveyed. Different encryption modes using Control Words of different lengths can thus be identified, allowing the receiver to identify (67) which of a plurality of decryption modes available to the receiver should be used (69) to decrypt the data.
A process for receiving encrypted data transmitted over a data network, the receiving process being arranged to decrypt the data in accordance with a Control Word and cipher decryption process, wherein the process is arranged to automatically identify a cipher encryption mode by which the data has been encrypted by identifying an inherent property of the Control Word which is characteristic of the encryption mode, and selecting, from a plurality of decryption modes, a decryption process operating in a decryption mode associated with the property so identified.
An apparatus for receiving and processing encrypted data transmitted over a data network, the apparatus comprising a receiver for receiving the encrypted data from an external source, a decoder for decrypting the data in accordance with a Control Word and cipher decryption process, and a processor for automatically identifying an encryption mode by which the data has been encrypted, the processor being arranged to analyse a Control Word associated with the received data by identifying an inherent property of the Control Word which is characteristic of the encryption mode and to select, from a plurality of decryption modes, a decryption process operating in a decryption mode associated with the property so identified.
Dependencies are inferred from the claim text.