Holographic encryption can be performed by employing encryption masks which alter the field before propagation. This makes the image

unrecognizable when recorded. You are given three holograms that represent the cipher image and three plain images and their holograms which were encrypted with the same encryption masks.
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I found masks that decrypt all three holograms to the given three plaintexts, but when I used the same masks to decrypt challenge hologram I got nonsense. How it could be? The description says all four plaintexts were encrypted with the same masks.

Can you confirm correctness of the challenge?

This is indeed weird, but I checked the challenge, and as far as I can see, everything seems fine. Are you sure that your masks can exactly recover the given plaintexts?

My masks are not exact, but recovered plaintexts are readable in all three test images except the fourth one. Anyway, I will try to find better masks.

My masks are not exact…

Then what is happening is expected. Masks providing only approximate solutions of known plaintexts are not necessarily expected to decrypt any given input.

The c source code in the additional zip file has been updated. The values in decryption were not exact, but it was always possible to solve the challenge, because nevertheless the signal was fully recognisable.

Best regards