| 摘要 |
The invention provides a method of transmitting a media work such as a movie to a client comprising the steps of (a) encrypting the work using a sequence of different keys corresponding to respective temporally spaced segments of the document, (b) transmitting software code containing an algorithm from a security server to the client, the algorithm having a result that is a function of the state of the client, (c) executing the code at the client and returning the result to the security server, (d) determining whether the result is indicative of an unmodified client, and further comprising the steps of: (e) transmitting a segment from a server to the client, (f) securely streaming a key corresponding to the transmitted segment from a secure remote server to the client, (g) decrypting the segment using the obtained media key, (h) if step (d) indicates a modified client, preventing further keys from being transmitted, otherwise repeating steps (e) to (g) and repeating steps (b) to (d).
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