Systems, methods, software, and components using tamper-proof real-time clock
View Patent ↗The write-access control line for an RTC is combined with a clear line for an RTC signature register, so that changes to the RTC will cause subsequent reads to return an invalidity flag.
1. A device, comprising:
instruction execution logic operable to execute a plurality of software instructions;
a real-time clock configured to maintain and provide a system time; and
a signature storage register having a write-access control line inaccessible to a user, wherein the signature storage register includes an invalidation control line connected to the real-time clock,
wherein the invalidation control line forces the signature register into an invalid state whenever the write-access control line goes active.
2. The device of claim 1 , wherein the real-time clock is configured to maintain the system time in nonvolatile memory.
3. The device of claim 1 , wherein the signature storage is configured to hold a digital signature for the real-time clock.
4. The device of claim 3 , wherein the digital signature is generated based on a unique hardware-encoded value.
5. The device of claim 3 , wherein the digital signature is generated based on a unique hardware-encoded value and a current system time.
6. The device of claim 1 , wherein the signature storage register is write only.
7. The device of claim 1 , wherein the invalidation control line is a clear input.
8. The device of claim 1 , wherein the invalidation control line is electrically connected to the write-access control line.
9. A method, comprising:
generating a digital signature for a real-time clock configured to maintain and provide a system time; and
storing the digital signature in a signature storage register having a write-access control line inaccessible to a user, the signature storage register including an invalidation control line connected to the real-time clock,
wherein the invalidation control line forces the signature register into an invalid state whenever the write-access control line goes active.
10. The method of claim 9 , wherein the real-time clock is configured to maintain the system time in nonvolatile memory.
11. The method of claim 9 , wherein the digital signature is cleared when the system time is modified.
12. The method of claim 9 , wherein the signature storage register is write only.
13. The method of claim 9 , wherein the digital signature is generated based on a unique hardware-encoded value.
14. The method of claim 9 , wherein the digital signature is generated based on a unique hardware-encoded value and a current system time.
15. The method of claim 9 , wherein the invalidation control line is a clear input.
16. The method of claim 9 , wherein the invalidation control line is electrically connected to the write-access control line.
17. A non-transitory computer readable medium comprising instructions for:
generating a digital signature for a real-time clock configured to maintain and provide a system time; and
storing the digital signature in a signature storage register having a write-access control line inaccessible to a user, the signature storage register including an invalidation control line connected to the real-time clock,
wherein the invalidation control line forces the signature register into an invalid state whenever the write-access control line goes active.
18. The non-transitory computer readable medium of claim 17 , wherein the real-time clock is configured to maintain the system time in nonvolatile memory.