Hey there! Here's a Digital Witness that has been shared with you:

Digital Witness

Issued to: WitnusApp user

In witness of the fact that data with the following digital fingerprint existed at the point in time below

Digital Data Fingerprint (Content ID)

a70e 1028 6635 5dc1 81c0 5f75 9515 c9a8 b72a 973a 050a 995e 03e2 72b3 fb21 864d 1953 2500 9732 2a20 3c5d 41fa 0400 2290 5919 058c d39c 131b bbc0 ab4c 4001 bfa4

Witness Fingerprint (Witness Id)

be79 8374 1514 56f8 51b7 ad06 3056 d1a9 5256 ffb1 0cc6 13df 65a2 3ae7 f523 7fd4 8489 25a5 e794 21d8 ab67 c8ee 578e e482 75a6 73e6 c736 c746 63b6 ea97 3398 c63d



A Digital Witness proves that something existed at a particular point in time. "Something" can be anything digital, in this case it's this video recorded by a user of the Witnus mobile app:
Here's a short description of the witness, from the person who shared it:
Rostning Butembo
This video was recorded on 9/9/2020 6:00:36 PM (Coordinated Universal Time, UTC)
It was recorded here:
If you want to convince yourself that the Digital Witness is legitimate you can validate it yourself, using tools that are freely available on the Internet. Do you want to view the instructions on how to do that?
The app calculates a "fingerprint" of the video file, and locks this fingerprint in a secure blockchain database to make sure it can't be manipulated. We call this fingerprint the Content Id, because it identifies the content.
A fingerprint is really a very large number, often presented as a long string of letters and numbers. In this case, that string looks like this:
That's pretty unreadable, so we've created an image matrix that represents that string in the form of an image instead. To compare two images, all you need to do is to drag one of them on top of the other. If they are identical, they will match up perfectly. If not, you'll notice because it looks like they are not properly aligned. Give it a try, just push one towards the other!
If the registered fingerprint matches the calculated, as it does here, it means that the content of the video has not been modified since the time and date the video was registered. Now let's validate that timestamp!
To do that, we again calculate a fingerprint. This time the fingerprint is based on a string that combines the first fingerprint, a signature that tells us who registered it, and the date and time this happened. Also, at the end of the string we tag on the Id of the user who created it, and the latitude and longitude where the witness was created. The combined string looks like this:
a70e102866355dc181c05f759515c9a8b72a973a050a995e03e272b3fb21864d1953250097322a203c5d41fa040022905919058cd39c131bbbc0ab4c4001bfa4#2020-09-09T18:00:39.1792458ZWitnusApp userUserIda8913545-1396-4bfc-b3bb-8cd7e6eedbacLatitude57.65728759765625Longitude11.945792855833705
We call the calculated fingerprint of this string the Witness Id, becuase it identifies the Digital Witness. For this particular witness, the Witness Id looks like this:
Again, comparing images is easier (and more fun) than comparing strings of letters, so here you go:
If you want to validate the fingerprints yourself, you can do so by using any service that calculates SHA512 hashes. That's the technical name for the fingerprints, and if you just search for "sha512 online" on the Internet you'll find a number of such tools that are free to use.
To calculate the Content Id fingerprint, you download the media above and upload it to the hashing service and let it do its thing. The result you're looking for is matching fingerprints, that's what tells you that the media file is exactly the one that was registered.
Validating the Witness Id is even easier, you just copy the combined witness string (the one that contains the Content Id, the Signature and the Timestamp, among other things) and paste it into your SHA512 calculator service. It should then print a string that is identical to the Witness Id above. If it does, you know that the timestamp in the witness is identical to the one you just copied and pasted.
The final step is to validate that the Witness Id also has been inserted into a blockchain database, so that you can validate the timestamp of the blockchain transaction. That process is described for this particular Digital Witness on the following page (fair warning, there's quite a bit of math on the page):