Method and apparatus for controlling access to digital signals

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United States Patent [i9]

Hamilton et al.

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US005504816A [ii] Patent Number: [45] Date of Patent:

5,504,816 Apr. 2, 1996

[54] METHOD AND APPARATUS FOR

CONTROLLING ACCESS TO DIGITAL
SIGNALS

[75] Inventors: Jeffrey S. Hamilton, Doylestown;

Marc Kauffman, Ft. Washington;
Lawrence D. Vince, Lansdale, all of
Pa.

[73] Assignee: GI Corporation, Hatboro, Pa.

[21] Appl. No.: 191,031
[22] Filed: Feb. 2, 1994

[51] Int. CI.6 H04L9/00

[52] U.S. CI 380/20; 380/49

[58] Field of Search 380/20, 49, 25;

341/63

[56] References Cited

U.S. PATENT DOCUMENTS

4,222,068 9/1980 Thompson 380/20

4,613,901 9/1986 Gilhousen et al 380/20

4,701,745 10/1987 Waterworth 341/63

4,817,146 3/1989 Szczutkowski et al 380/49

5,138,659 8/1992 Kelkaretal 380/20

5,144,664 9/1992 Esserman et al 380/20

5,153,918 10/1992 Tuai 380/25

5,173,775 12/1992 Walker 358/141

5,173,900 12/1992 Miller et al. .

5,230,019 7/1993 Yanagimichi et al. .

5,235,641 8/1993 Nozawa et al 380/49

5,301,245 4/1994 Endoh 380/20

5,341,425 8/1994 Wasilewski et al 380/20

OTHER PUBLICATIONS

J. Vigarie, "A Device for Real-Time Modification of Access
Conditions in a D2-MAC/Packet Eurocrypt Signal: The
Transcontroller," 18th International Television Symposium
and Technical Exhibition, Jun. 10, 1993 -Jun. 15, 1993,
Montreux, Switzerland, pp. 761-769.
"Proposal to Cable Television Labs, Inc, PBS, TeleCom Inc,
Viacom for DigiCipherTM Digital Compression Program
Delivery System," General Instruments Corp., Video Cipher
Division, San Diego, CA, Nov. 27,1991, pp. 1-vi, 6,11,12,
17, 20, 50, 51, 52, 53.

Primary Examiner—Salvatore Cangialosi

Attorney, Agent, or Firm—Barry R. Lipsitz; Ralph F. Hoppin

[57] ABSTRACT

A method and apparatus are provided for controlling access to digital signals sent via a first communication path and retransmitted over a second communication path. The digital signals, having been encrypted by a first encryption scheme and sent over the first communication path, are received and decrypted. The decrypted signals are then retransmitted over the second communication path using a second encryption scheme that differs from the first encryption scheme.

15 Claims, 4 Drawing Sheets