Secret Pictures

Rotate the table, find the correct top layer that reveals a secret image.

Find all three secret images.

This is a way to split a secret between two or more people. The people must cooperate to get the secret. Can you think of a situation that needs people to agree before a secret is revealed?

Visual cryptography is a way to send a secret when you don’t want lots of difficult calculations! Visual cryptography uses two images that appear to be random black and white pixels. However, when the two layers are stacked, a secret picture is revealed. The secret image is split so that the black and white pixels are shared between the two layers. There is no way to know what the secret image is from just one layer.

Visual cryptography can be designed to split the image across many layers so that all layers are necessary to reveal the image. Alternatively, the layers can be designed in such a way that any two layers are enough to reveal the secret. This allows many people to have one layer of the image, but the secret is only revealed when people cooperate.