http://www.newscientist.com/article/dn16109-laser-trick-churns-out-secure-random-numbers.html?DCMP=OTC-rss&nsref=physics-math Laser trick churns out secure random numbers * 18:00 23 November 2008 by Colin Barras Generating random numbers is harder than you might think, and the security of digital communications depends on it. Now a new method that uses lasers to produce streams of truly random numbers faster than ever before could help improve security at a time when digital traffic and cybercrime are both growing. Strings of random numbers are used to make secret keys and other parts of encryption protocols. But software that generates random numbers can generally only manage a close approximation to random. Statistical analysis reveals underlying if near-invisible patterns that mean an attacker could predict the sequence and break the code. Innovative ideas like tuning into atmospheric noise are sometimes used instead to achieve true chance. Now a new trick using the semiconductor lasers that power fibre-optic links offers a more practical way to improve security. Welcome feedback The new system can generate truly random numbers 10 times faster than existing devices, which can typically only produce 10s or 100s of megabits of random numbers per second, says Atsushi Uchida, an electrical engineer at Saitama University, Japan. Uchida and colleague Peter Davis, from NTT Communication Science Laboratories in Kyoto, can now generate truly random sequences at up to 1.7 gigabits per second. They took a standard semiconductor laser and added an external mirror to reflect some of the light back inside the laser. That feedback causes the light produced to oscillate randomly. This can be converted into an AC current and then into a binary signal that can be used by a computer. Signals from two lasers are combined into a single, truly random number sequence. Relatively inexpensive versions of the system could be built into cryptographic systems for secure network links, or quantum communication systems, say the researchers. Journal reference: Nature Photonics (DOI: 10.1038/nphoton.2008.227)