Cryptography – Key management – Key distribution
Reexamination Certificate
2011-08-09
2011-08-09
Barron, Jr., Gilberto (Department: 2432)
Cryptography
Key management
Key distribution
C705S055000, C726S027000
Reexamination Certificate
active
07995763
ABSTRACT:
A user apparatus cannot acquire as many distribution keys Ki, . . . as a threshold value, to restore a content encryption key KM, unless it decrypts as many encrypted sub-content items as the threshold value after it has played back a sub-content item SC1. The user apparatus monitors the state in which the sub-content is being played back. It outputs a warning when the sub-content is in fast-forwarding state or skipping state. If the playback state is not returned to one before the fast forwarding or skipping, in spite of the warning, the user apparatus will erase the distribution keys acquired in the fast-forwarding state or skipping state.
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patent: 2005/0018854 (2005-01-01), Yamamoto et al.
patent: 2006/0282389 (2006-12-01), Gupte
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Ad Shamir, “How to Share a Secret”, Programming Techniques, vol. 22, No. 11, Nov. 1979, pp. 612-613.
Barron Jr. Gilberto
Cribbs Malcolm
Kabushiki Kaisha Toshiba
Oblon, Spivak McClelland, Maier & Neustadt, L.L.P.
Toshiba Solutions Corporation
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