Method and system for regulating access to a service

摘要

To regulate access to a service provided by a service provider, a service authoriser generates for each of multiple service time periods a different respective data set comprising private data and related public data. The service provider uses the public data for a current time period and an encryption key string to generate encrypted data which a party wanting to receive the service must decrypt. The service authoriser provides a decryption key to the party after determining that the party is entitled to receive the service for a particular service time period; the decryption key is generated using the aforesaid encryption key string and the private data of the data set for the service period concerned. The party can then decrypt the encrypted data it receives provided that the period for which the data has been encrypted is the same as that for which the decryption key was generated.