Abstract: An apparatus and method produce a videotape or other recording that cannot be pre- or post-dated, nor altered, nor easily fabricated by electronically combining pre-recorded material. In order to prevent such falsification, the camera or other recording apparatus periodically receives certifiably unpredictable signals ("challenges") from a trusted source, causes these signals to influence the scene being recorded, then periodically forwards a digest of the ongoing digital recording to a trusted repository. The unpredictable challenges prevent pre-dating of the recording before the time of the challenge, while the storage of a digest prevents post-dating of the recording after the time the digest was received by the repository.

Abstract: A method and apparatus authenticates and provides non-reputability for analog messages which renders it impossible for a person, including the recipient, who is not in possession of a (cryptographic) key belonging to the claimed sender, to forge the message. The recipient is able to verify that the sender possessed the correct key, and a third party (judge) can establish whether the message was forged or not. This is accomplished by interposing a digital signature generator/verifier/recorder (DS-GVR) module in the sending apparatus, such as a facsimile machine. The receiver, using another DS-GVR, can verify that a received document comes from the purported sender and has not been altered enroute. The receiver's DS-GVR module can be made to produce a machine-readable record of the signed transmission.