| 摘要 |
The teachings herein present a method and apparatus for protecting usage restriction data that governs usage of an electronic device. A cryptographic circuit supports secure and non-secure accesses. When non-securely accessed, it is operable only to verify the stored usage restriction data, and, when securely accessed, it is operable to generate a new message authentication code for changed usage restriction data, for subsequent authentication of that data. The usage restriction data may be stored in non-secure memory and may include static and dynamic parts. One or more embodiments include a secure circuit indicating whether the device has been initialized. The cryptographic circuit outputs a message authentication code for the static part using a permanent device key from the secure circuit, only if the device has not been initialized, and outputs a message authentication code for the dynamic part as needed to support authorized changes to the dynamic part. |
