Patent ID: 8176330

Claim:
A method of producing certifications of digital files, the method comprising: from time-to-time in an on-line mode, receiving a certified time stamp at a tamper-resistant portion of a processor of a tamper-resistant certification device from a remote source remotely located with respect to the tamper-resistant certification device; in response to receiving the certified time stamp, providing a time stamp receipt to the remote source from the tamper-resistant portion of the processor; and from time-to-time, in an off-line mode, receiving a digital file for certification at the tamper-resistant portion of the processor via a non-tamper resistant portion of the processor; determining a temporal offset from a last receipt of one of the certified time stamps received at the tamper-resistant portion of the processor; and producing a certified digital file comprising the contents of the digital file, the time stamp receipt, and an indication of the determined temporal offset from the last receipt of one of the certified time stamps.