Patent ID: 8369524

Claim:
Method for transmitting encrypted data scrambled using a control word in a communication network comprising a device of a first type containing: a first symmetric key for encrypting a control word sent to a device of a second type connected to the network, wherein said second type of device is a different device type from said device of the first type; and and an encrypted first symmetric key which is generated from the encryption of said first symmetric key with a second symmetric network key known only by the device of the second type connected to said network; the method comprising the steps for the device of the first type of: (a) generating a random number; (b) computing a new symmetric key as a function of the first symmetric key and said random number; (c) encrypting the control word used to scramble the data to be transmitted with the new symmetric key; and (d) after steps a, b, and, c; subsequently transmitting to the device of the second type, via said network: the control word encrypted with the new symmetric key; the data scrambled using the control word; the random number; and said encrypted first symmetric key.