The final solution for Verisign and others is to insert a integral generator of code to the Operating System for it to generate a code for changes to system time as this is critical for checking the genuiness and non-manipulation of documents in document systems!
The code generator is to be encapsulated (self-destroy on intrusion attempts, with source-code hidden or encoded from the production line) and then integrated with the Operating System. This will make it certain on a 15 ciphers/types/letters code that the system time is the SAME now as before, once the system has been set into place!
Note: this comes in addition to setting system to hundreds of a second, making it very difficult even then to change the system time for the documents to display a change of modification, that is "the document has been created [date/time]" and "the document has been changed [date/time]"! Good?