A long-standing problem in cryptography has been the sharing of secrets (understatement of the century, right?) Assuming that your communication medium can't be trusted because anyone and everyone could be listening in, how do you distribute keys to everyone you want to securely contact? The most obvious method is to meet up with everyone and hand them the keying material personally. However that way fraught with problems, from your courier getting ganked for the keying material to a simple matter of common sense: if you're going to meet with the intended recipient, why not just tell them and not bother …

The pattern of light on the wall was made by a ray of early morning sunlight that bounced off of a fishbowl (out of frame). The shape of the pattern is what caught my eye.