Few of us would care if our house keys appeared in a photograph of the family picnic posted on the internet.

But we should be concerned because advances in digital imaging and optics means any photograph of a key posed a potential security threat, Stefan Savage, a computer science professor at the University of California, warns.

Professor Savage and two of his PhD students have developed a software program called Sneakey that can clone a key in "two to three minutes" after analysing a digital photograph.