digital signature - Is it possible to make a video that is provably non-manipulated?

digital signature – Is it workable to make a video that’s provably non-manipulated? Answer

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digital signature – Is it workable to make a video that’s provably non-manipulated?

I cerebrate, if you happen to proceed down this line of pondering, you’ll finish up with one thing similar to Trusted Timestamping Servers.

The gist thought of trusted timestamping is that you simply capitulate a file to the server and it indicators an attestation maxim that it noticed the file with hash aabbcc112233 at time X. This is often used for each proving the preliminary publication time (and who revealed it), in addition to proving that the file has not been modified since.

You necessity the trusted third occasion as a result of if the end-user creating the video is the identical individual signing it, then there’s nothing stopping them from re-signing it after they edit it.


That stated, I do not cerebrate you actually necessity any care for crypto right here; the best resolution might be finest. Have the scholar live-stream their cameras to an exam-monitoring web site. The web site logs the video stream in its database because it is available in, and it could actually detect and alert if the dwell stream had any breaks or disruptions lengthy sufficient for guide modifying to doubtlessly have taken place.


Update addressing feedback.

Ah, you could have the spare privateness requirement that college students don’t need their video saved on third occasion servers (that ought to have been within the query!).

In that illustration, what makes this drawback difficult is that you would be able to’t abide till the finish of the examination and publish a sole hash for the gross video as a result of that offers the scholar too mighty time to edit a center part of the video. The resolution that involves intellect would breathe some kindly of hash-block-chaining (not “The Blockchain (Bitcoin)” however “a blockchain”). Either the sender or receiver breaks the video stream into, for instance, 10 s “blocks”, hash every dam as they’re produced/recieved, and stream the hash for every dam together with the video in real-time. You do “block-chaining” by together with in every dam the hash of the earlier dam. In math notation:

h_0 = hash(videoblock_0)
h_1 = hash(videoblock_1 || h_0)
...
h_n = hash(videoblock_n || h_n-1)

This preserves privateness as a result of the server solely must retailer the hashes and never the video itself. This is streaming-friendly since you are producing hashes all through the stream and every hash covers the gross stream as much as that time. This is environment friendly as a result of the server solely must retailer the latest hash (h_n), and that is sufficient to later confirm if a offered video was tampered with at any level within the stream (although to detect the place it was tampered you’ll necessity to rescue each dam hash).

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