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)

9ac1 54ed 09a2 6ae1 ab1d f250 25ce 603d 3e2f cee4 1b95 2086 625e 9981 d76b ba82 30be 8b18 eca7 1df5 fadf 4925 dd83 8858 bd71 a8a0 53f1 d6ab 87c4 5186 e41b 22a1

Witness Fingerprint (Witness Id)

d8e4 ac58 05dd ba4c ec43 1724 7952 8554 2d7c 2140 a901 b3be 8a76 201d 9e35 ab81 f7f1 3f9b 0fff 01b8 1c93 4e01 df5b 115f a5cf e248 68ff ada3 e56b 9f2b b6ac c00e



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:
Okapi kyler ned efter rostning
This video was recorded on 9/9/2020 6:37:51 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:
9ac154ed09a26ae1ab1df25025ce603d3e2fcee41b952086625e9981d76bba8230be8b18eca71df5fadf4925dd838858bd71a8a053f1d6ab87c45186e41b22a1#2020-09-09T18:37:52.0797094ZWitnusApp userUserIda8913545-1396-4bfc-b3bb-8cd7e6eedbacLatitude57.657257080078125Longitude11.945832750793592
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):