| 摘要 |
A content distribution system includes a management device and a viewing device. The management device manages encrypted content information. The viewing device acquires the encrypted content information from the management device, decodes the encrypted content information, and allows the decoded content information to be viewed. The management device includes a view control information issuing unit. Upon receipt of a request from the viewing device to issue view control information, the view control information issuing unit issues view control information including decryption key information corresponding to an (i)-th random number corresponding to an ordinal number (i) among plural random numbers and period-of-validity information about a period of validity. The plural random numbers are shared between the management device and the viewing device. The viewing device includes a storage unit, a counting unit, a holding unit, a request unit, a calculation unit, a display controller, an update unit, and a deletion unit. |
