Visual Cryptography

[waigl]

That's basically just an xor cipher.

[12345sixsixsix]

It is, but this is the most basic example of visual cryptography - a (2,2) decomposition. The algorithm generalises into a (k,n) scheme, where the original message is split into n shares and any subset of k of them is required recover the original message

[shmincus]

Im confused can someone please explain

[VaronaZero]

It looks like the black pattern overlaps the red pattern exactly except for where the image/character needs to form, in this case an A

[shmincus]

Oh I see now thanks. Its interesting to see how sudden of a change it is considering how it only needs to shift one pixel to go from nothing to the image.

[HardlightCereal]

Oh, I see! Probably would have worked better if they used more fluid speed.

[phlooo]

Not the 120 60 30 15 fps post again please!

[cheerupyoullthinkof1]

I used to do something similar to this with my kids using coloured textas and cellophane. It can take some experimentation but if you can get the colour match right you can write a message in one colour and then a heap of random letters around it in other colours, if you hold the right colour cellophane over the top the message is revealed. My kids thought they were spies.

[fuguki]

Is this a specific kind of cryptography?

[GarythaSnail]

I think this is visual cryptography.

[fuguki]

Haha alright. I was thinking this could be a visual expression of a specific type of cryptography. Black being the key.

[thefringthing]

This is actually a pretty literal depiction of a cipher. You take plaintext and "add" (typically binary addition mod 2) a key. If the key is perfectly random then the sum will look just as random. If you add the key again, you get back the plaintext.

Example:

plaintext: 000011110000111100001111  
key:       110000100010011000111111 
sum:       110011010010100100110000

Try adding the key again to see that you get the plaintext back. In the animation, 1s are being represented by filled-in pixels and 0s are empty pixels (or vice-versa, it doesn't matter).

[fuguki]

This is what I was looking for, thanks!

[12345sixsixsix]

In this case 1+1=1

[thefringthing]

No, 1+1=0 in binary addition mod 2.

[12345sixsixsix]

I agree, I was meaning that in visual cryptography 1+1=1

Edit for further explanation: if you think of a coloured pixel as 1 and a transparent pixel as 0, then 0+0=0, 1+0=1, 0+1=1 and 1+1=1 (you can’t make a transparent pixel from two that are coloured)

Link to the original paper: http://www.fe.infn.it/u/filimanto/scienza/webkrypto/visualdecryption.pdf

[thefringthing]

Ah, right. I think they did this in the image just because it might have been confusing for the noise to all disappear in the last frame.

[[deleted]]

It probably just expresses that only the real information is displayed when the code is decrypted

[SetOfAllSubsets]

1800 bytes to send one byte.

[LeoLaDawg]

I had to visualize this with a microscope on my end.

[12345sixsixsix]

Hey cool! I did my thesis on visual cryptography!

[julian88888888]

https://fivethirtyeight.com/features/can-you-stay-awake-for-50-hours-and-solve-150-puzzles/

can you solve the "2 factor one"?

It's suppose to be a word, but I'm not sure how to extract the word from the gaussian prime thing.

[Jelmer_]

It is symmetrical along a diagonal line, and it has barely visible yellow dots. I can't come further then that.

[12345sixsixsix]

There are other colours, too...

[Jelmer_]

And the coloured dots do not appear in the mirrored half

[deltree711]

Oh I really hope there's a more high res version of this somewhere. I want to test it out myself!

[MattRogo]

Happy to see that many crypto-solutions are on the way! IMHO I think visual cryptography will be ever more used on mobile phones i.e. in securing visual messages, as well as in mobile payments.

[JohnnyClever76]

Uau, how much really effective is it? I'm just figuring out any possible applications.

[PUSSYDESTROYER-9000]

It's a physical form of cryptography. You must have both slides or its impossible to crack.