| 摘要 |
A software product is modified so that it can be freely distributed while limiting its use to authorized subscribers. The modification includes replacing calls to relocatable subroutines in the software product by calls to redirection software, which is added to the software product together with authorizing software. A table of information on the replaced calls is supplied securely to an authorization agent, with which the authorizing software communicates on execution of the modified software product. An authorized subscriber supplies local data specific to its environment to the authorization agent, which encodes the table in dependence upon the local data and the authorizing software and supplies it to the authorized subscriber. Tampering with the authorizing software, or different local data of others, prevents use of the table. The redirection software decodes a target address for each replaced call during execution of the software, without decoding of the table or restoring the software to its original form. Alternatively, the redirection software can be supplied to the authorized subscriber by the authorization agent.
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