A
system and methods for proving dates of
digital data files, which are accessed, created, modified, received, or transmitted by a computer includes a trusted time source in a tamperproof environment, a first subsystem for saving the file at a moment in time, a second subsystem for retrieving from the trusted time source a date and a time corresponding to the moment in time, a third subsystem for appending the date and the time retrieved from the trusted time source to the saved file, a fourth subsystem for signing the saved file with the date and the time retrieved from the trusted time source appended thereto, a fifth subsystem for hashing the signed file to produce a digest, a sixth subsystem for signing the digest with a key to produce a
certificate, a seventh subsystem for appending the
certificate to the saved file, and an eighth subsystem for saving the file with the
certificate appended thereto. The trusted time source is a
real time clock, which is not resettable, is independent of any
system clock of the computer, and is installed locally relative to the computer.