Visual cryptography (invented by Naor & Shamir in ; read their seminal paper or a locally cached copy) is a method for securely encrypting messages in. Visual cryptography is a cryptographic technique which allows visual information (pictures, text, etc.) to be encrypted in such a way that decryption becomes the job of the person to decrypt via sight reading. One of the best-known techniques has been credited to Moni Naor and Adi Shamir, who developed it in ‎Example · ‎(2, N) Visual · ‎Cheating the (2,N) Visual · ‎In popular culture. Abstract: Visual cryptography is a cryptographic technique which allows visual information to be encrypted in such a way that decryption becomes a mechanical.


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Every pixel from the secret image is encoded into multiple subpixels in each share image using a matrix to determine the color of the pixels.

In the 2,N case a white pixel in the secret image is encoded using a matrix from the following set, where each row gives the subpixel pattern for one of the components: Mysteriously, however, if the two grids are overlaid correctly, visual cryptography just the right position, a message magically appears!

visual cryptography

Visual cryptography - Wikipedia

The patterns are designed to reveal a message. Below you will see two random looking rectangles of dots. One is fixed in the visual cryptography, and visual cryptography other you can drag around the canvas.

As the rectangles intersect, the images merge. If you align the rectangles perfectly, a hidden message will appear.

Visual cryptography

First we take a monochrome visual cryptography for the source. Pixels in the image are visual cryptography white or black. To the right is the source for the first example we saw above. Next we sub-divide each pixel into four smaller subpixels.

Visual Cryptography Kit

We need to shade these four subpixels to represent the source image, then subjectively divide them between the two cypher images we are to create. We need to distribute the shading such that, if you have just one of the cypher images, it is impossible to determine what is on the other cypher visual cryptography, and thus, impossible to decrypt the image.

What visual cryptography do is look at the color of each pixel in the original source image.

If the original pixel in visual cryptography image is set blackwe fill in all four sub pixels then distribute them two per cypher layer. One cannot know if a pixel in layer 2 is used to create a grey or black pixel, since we need the state of that pixel in layer visual cryptography which is random to know the overlay result.

If all requirements for true randomness are fulfilled, Visual Cryptography offers absolute secrecy according to the Information Theory.

If Visual Cryptography is used for secure communications, the visual cryptography will distribute one visual cryptography more random layers 1 in advance to the receiver.

If the sender has a message, he creates a layer 2 for a particular distributed layer 1 and sends it to the receiver.


The receiver aligns the two layers and the secret information is revealed, this without the need visual cryptography an encryption device, a computer or performing calculations by hand. The system is unbreakable, as long as both layers don't fall in the wrong hands.

Visual Cryptography

When one of both layers is intercepted it's impossible to retrieve the encrypted information. January 13, I just learnt about visual cryptography coolest thing.

The figure shows how a pixel in a image in divided into two sub pixels depending on whether the pixel is black or white. By doing so the width of the share increases. visual cryptography

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This is termed as Pixel Expansion. Figure 2 shows visual cryptography problem of Pixel visual cryptography where a Pixel in the image is divided into 2 sub pixels which increase the width of the entire image and thus there will be increase in bandwidth required and so increase in the power consumption.

Each pixel is being handled separately. The input is a secret image and the output is the shares.