What do encryption and Superman have in common? Like the Man of Steel, encrypted information can now travel at the speed of light. Scientists at Northwestern University can protect data by transforming encrypted material into pulses of light. Called quantum cryptography, the technique sends the light pulses over fiber-optic lines at 250Mbps. Users get keys to encode and decode the encrypted information. The data is sent within bursts of light. If anyone tried to crack the code, there would be nothing to see, not even the 1s and 0s composing the algorithms on which other encryption technologies are based. "The only way a hacker could get around the protections of light would be to break the physical laws of nature," says Prem Kumar, professor of electrical and computer engineering and physics and astronomy at Northwestern. "These laws have stood the test of time for 100 years."Funded by a grant from the U.S. government's Defense Advanced Research Projects Agency, Kumar's research, and its apparent invulnerability to hacks, will be of interest to the military. Northwestern is also working with BBN Technologies to commercially market the technique. However, quantum cryptography does have its limitations. To date, the technology has only been tested over a maximum of four kilometers of fiber; most fiber-optic networks stretch over hundreds or thousands of miles. And while 250Mbps is more than 1,000 times faster than previous attempts at quantum cryptography, it's considered relatively slow compared with the speed of data over fiber-optic lines.