Multiple keys for decrypting data in restricted-access...

Details Multiple keys for decrypting data in restricted-access... Multiple keys for decrypting data in restricted-access...

1997-03-04

2004-02-10

Hayes, Gail (Department: 2131)

Cryptography

Video cryptography

Copy protection or prevention

C380S210000, C380S223000, C380S276000, C380S278000, C380S284000, C380S286000

Reexamination Certificate

active

06690795

ABSTRACT:

BACKGROUND OF THE INVENTION
Existing cable television systems (1) scramble programs, (2) transmit the scrambled programs to customers, and (3) provide the customers with “set-top boxes” for unscrambling the programs. Many such television systems operate in the analog signal domain.
However, digital signal transmission is coming into widespread use. Digital signal transmission possesses characteristics which are different from analog signal transmission. The invention presents novel modes of transmission and encryption which are especially suited to the unique capabilities of digital signal transmission.
SUMMARY OF THE INVENTION
In one form of the invention, multiple decryption keys are used to decrypt encrypted material which is transmitted to customers of a restricted-access television system.


REFERENCES:
patent: 5237610 (1993-08-01), Gammie et al.
patent: 5389738 (1995-02-01), Piosenka et al.
“Applied Cryptography,” Second Edition, by Bruce Schneier, pp 265-278 and 357-363, 1995.

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