A smart card system and methods for proving dates of digital data files
includes a trusted time source, 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. All of the subsystems are preferably sealed
together within a smart card.
