There's always the risk with any wireless communication that an eavesdropper will intercept your message, so encryption is a must, but that means securely exchanging an encryption key beforehand. The current solution often requires users to manually enter a key - think pairing two Bluetooth devices with a four-digit code - or simultaneously press a button on both devices, but this exchange could also be snooped on by a determined attacker.
Now researchers at the University of Trieste, Italy say they have come up with a colorful solution that can't be intercepted. Eric Medvet and colleagues have encoded the encryption key as flashes of color on the screen of one phone that are picked up by the camera of another, in a system they call Rainbow Crypt.
http://www.newscientist.com/blogs/onepercent/2011/11/secure-communications-with-a-r.html
