Cryptography – Particular algorithmic function encoding – Nbs/des algorithm
Patent
1985-02-22
1988-04-05
Buczinski, Stephen C.
Cryptography
Particular algorithmic function encoding
Nbs/des algorithm
380 21, 380 10, H04N 7167, H04L 902
Patent
active
047364220
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the broadcasting of a television signal in scrambled form and more particularly to a system for enabling the scrambled television signal to be descrambled by authorised viewers only.
It has already been proposed to broadcast scrambled television signals. It has also been proposed to transmit with the scrambled television signal the key for descrambling the signal but the key is encrypted by a further key, an identification key, which is unique to each viewer. In order to decrypt the key the viewer must use his identification key signal and await the broadcast encrypted key.
This is acceptable as long as the number of viewers is not considerable but where one is broadcasting to a considerable number of viewers, for example with satellite broadcasting, it can take a considerable time to access all the viewers with their own encrypted key signal to enable them to descramble the broadcast television signal. While this problem can be overcome by leaving the receiving apparatus powered up continuously, this is not a convenient or inexpensive solution to the problem. Furthermore, when the receiver is first purchased a long waiting time results.
It is an object of the present invention to provide a system for sending encrypted programme entitlements together with a period key to one of a large number of viewers in such a way that he can relatively quickly access the encrypted entitlements and period key which enable him to decypher the scrambled teleivision signal. The period key (P) is also known as the authorisation key (A), but it will be called the period key here.
The present invention provides for sending to a plurality of viewers their individual programme entitlement and the period key, encrypted together as one cipher text block by means of a single distribution key which is used by each viewer to obtain the necessary information for descrambling the television signal. Hence the distribution key and the cipher text block is shared between the plurality of viewers. The sharing of information in this way enables a reduction in the total means of bits that have to be transmitted without compromising the security. The reduction of bits occurs because in a shared block, only one period key needs to be sent and its overhead is shared. If the cipher text block was not shared a separate period key, which needs to be a large number of bits, would have to be appended to each viewers entitlements for reasons of security.
The present invention also provides a secure scrambling system for apparatus for transmitting a scrambled information signal comprising means for generating a first encryption signal (S), first encryption means for encrypting the information signal in accordance with the encrypting key signal (S), means for generating a second encryption key signal (P), second encryption means for encrypting the first encryption key signal in accordance with the second encryption key signal (P), means for generating a third encryption key (D), third encryption means for encrypting the second encryption key signal (P) in accordance with the third encryption key signal (D), and means for transmitting the scrambled information signal and at least the encrypted second encryption scrambling key signal.
Features and advantages of the present invention will become more apparent from the following description of an embodiment thereof given by way of example, in which:
FIG. 1 shows a block diagram of an encryption system;
FIG. 2 shows the structure of one part of one of the signals sent in the system shown in FIG. 1;
FIGS. 3a and 3b show diagrammatically two ways of implementing a part of FIG. 2; and
FIG. 4 shows a method of replacing shared distribution keys.
A preferred embodiment of the present invention will be described in relation to an over-air addressing DBS television encryption system as shown in FIG. 1. A subscriber cannot make use of a conditional access television programme without being in possession of the key that was used for the signal encryption. Furthermore, this key must
REFERENCES:
patent: 4292650 (1981-09-01), Hendrickson
patent: 4352011 (1982-09-01), Guillou
patent: 4388643 (1983-06-01), Aminetzah
patent: 4484027 (1984-11-01), Lee et al.
patent: 4531020 (1985-07-01), Wechselberger et al.
patent: 4531021 (1985-07-01), Bluestein et al.
patent: 4536791 (1985-08-01), Campbell et al.
patent: 4613901 (1986-09-01), Gilhousen et al.
WO, Al, 83/01881 (Communications Satellite Corporation), 26 May 1983; see p. 4, Line 1--p. 8, Line 7; p. 9, Lines 25-29.
EP, Al, 0014654 (Telediffusion de France), 20 Aug. 1980, see p. 7, Line 11--p. 8, Line 26.
WO, Al, 83/04154 (Telease), 24 Nov. 1983, see p. 4, Line 5--p. 7, Line 25.
Buczinski Stephen C.
Independent Broadcasting Authority
Koltak Melissa L.
LandOfFree
Encrypted broadcast television system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Encrypted broadcast television system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Encrypted broadcast television system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2239104