Cryptography – Key management
Reexamination Certificate
2002-06-26
2008-09-23
Moazzami, Nasser (Department: 2136)
Cryptography
Key management
C380S201000, C380S203000, C380S230000, C380S270000, C713S155000, C713S156000, C713S175000, C713S158000, C726S026000, C726S028000, C705S051000, C705S055000, C709S204000, C709S231000
Reexamination Certificate
active
07428307
ABSTRACT:
A decryption processing unit decrypts encrypted content data using a license key Kc. When an elapsed time after reception of the license key (Kc) does not exceed a hold time at a time of the license key (Kc) included in reproduction control information (ACp), reproduction of encrypted content data continues. When the elapsed time exceeds the hold time at a time, the license key (Kc) is discarded, and a reproduction control unit again obtains a license key (Kc) from a memory card. Discarding and reobtaining license key (Kc) continues until an allowable output count of license key (Kc) from the memory card becomes zero. As a result, a reproduction time of encrypted content data can be controlled safely.
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Hasebe Takayuki
Hirai Tatsuya
Hori Yoshihiro
Abedin Shanto
Fujitsu Limited
Hitachi , Ltd.
McDermott Will & Emery LLP
Sanyo Electric Co,. Ltd.
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