Trusted Camera - Online Version

This version uses a trusted time service to add verifiable timestamps to the signed images.

A "trusted time service" uses a accurate clock, such as GPS or atomic clock corrected, and a digital signer to provide verifiable timestamps.


The time service guarantees that the image was signed at time T, hence it must have been taken prior to that time. In the absence of tampering with the camera, it can be stated that the image was taken shortly before time T. For greater timekeeping accuracy, the camera may obtain transmission-delay corrected time from the time service using a method such as NTP, and add it to the camera metadata, or an onboard clock may be used and calibrated offline.

An example of a commercial timestamping service may be found at

For still images, a checksum may be sent to the timestamp service for each image.
For video, checksums for a group of frames (a second, or a minute) may be sent for timestamping, or only one frame in 100 may be timestamped and times for other frames may be interpolated. The signature object for a video file is thus more complex than for a still image file.


The camera may be used to created a timestamped image of a printed photograph or delayed video, and thus make it appear that the event took place later than it in fact did.

Back to Main Page