Cryptography – Key management
Patent
1998-04-24
2000-09-12
Barron, Jr., Gilberto
Cryptography
Key management
380239, H04L 908
Patent
active
061188735
ABSTRACT:
A digital broadcast system provides secure transmission of digital programs to in-home digital devices even when some of the devices are unauthorized. A matrix of device keys S.sub.j,i is provided, wherein "i" is a key index variable indicating a position in a key dimension of the matrix and "j" is a sets index variable indicating a position in a sets dimension of the matrix. Each in-home device is assigned plural device keys from the matrix, with one and only one device key for each key index variable "i" being assigned to a device. To generate a session key for a broadcast program, session numbers x.sub.i are encrypted with all device keys S.sub.j,i to generate a session key block which is decrypted by the in-home devices and used to generate a session key for decrypting the program. If one of the devices is a compromised device, at least one of the session numbers is a dummy number that is encrypted and decrypted by the corresponding compromised device key, with the resulting session key being useless in decrypting the program.
REFERENCES:
patent: 4694491 (1987-09-01), Horne et al.
patent: 5345505 (1994-09-01), Pires
patent: 5592552 (1997-01-01), Fiat
Internet "Copy Protection Gets Serious Illegal Copying of Movies and Music", Feb. 19, 1998. (http://cnn.com).
Internet "Technology of the Year Firewire/IEEE 1394", Mar. 3, 1998. (http:/
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Lotspiech Jeffrey Bruce
McCurley Kevin Snow
Barron Jr. Gilberto
Hall David A.
International Business Machines - Corporation
Rogitz John L
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