1.7 GBit/s RNG by laser feedback

[Eugen Leitl]

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)