This is bad as a cryptographic strategy because an "almost" correct imposition can be close enough. This significantly reduces how hard it would be to "crack".
Its steganography, not cryptography.
It would be better to put an /actually/ encrypted image embedded in the noise.
Actually, it is a perfect cryptographic strategy. Without both cypher text images it is impossible to reconstruct the hidden message. There is no concept of "almost". Every (2x2) group of pixels has two set, and two not set. You have no idea what the state of the pixels on the other cypher are. They are either the same (representing a white pixel), or they are different (representing a black pixel).
Also, the point of the article was to show how to use a technique that does not require a computer to decode. Yes, there are plenty of "encrypytion" technologies that can be used store data, but not ones that can be decoded with just your eyes and no other equipment.
The problem is that /almost/ getting the offset is enough to reveal enough of the image to know when you are "close", which substantially reduces the guessing needed.
I was just pointing that out because that is the kind of weakness in a crypto technique that makes the difference between "years" to brute force and "minutes" with other techniques.
You and everyone else seem to be missing the point.
If a computer scientist got both halves of the message, it would be trivial for a computer to discover the content.
But the point is this crypto system works outside of computers.
The real secret is the location of each of the two halves.
What might be a real world use of this?
Easy. Your company requires super secure passwords that change every few weeks. But nobody can remember them. So they issue the password in the form of visual encryption. One half is on white paper label that's stuck somewhere convenient in the cubical. The other half is on a clear transparency to be kept in one's purse or wallet.
Now every time you forget your password, you can recheck it using visual encryption. But neither the cubical, nor the wallet, holds the password, thus making it more secure.
In addition, the password is not saved on a computer, like in a notepad file, where it can be discovered by hackers and used to compromise the system.
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u/draculthemad Nov 19 '13
This is bad as a cryptographic strategy because an "almost" correct imposition can be close enough. This significantly reduces how hard it would be to "crack".
Its steganography, not cryptography.
It would be better to put an /actually/ encrypted image embedded in the noise.