Ivars Peterson
Sealed within a transparent, tapered, liquid-filled
cylinder, illuminated colored globs slowly rise and fall. Meandering and
deforming, their shapes and paths change unpredictably. Invented in 1963, a
decorative fixture in many homes during the 1970s, and still in production,
Lava Lite lamps are now the object of renewed curiosity.
Indeed, researchers have come up with a novel application of
the mesmerizing movements of the lamp’s globules. They use them as the
starting point for generating a sequence of random numbers. Called Lavarand,
the random-number generator is the tongue-in-cheek work of Robert G. Mende
Jr., Landon Curt Noll, and Sanjeev Sisodiya of Silicon Graphics in Mountain
View, Calif.
Random numbers are an immensely valuable commodity, not only
for the operation of computer-based slot machines but also for computer
simulations and for generating the secret strings of digits required to encode
and decode sensitive information in cryptographic systems.
The trouble is that no numerical recipe used by a computer
produces truly random numbers. The computer simply follows a set procedure,
and restarting the process with the same initial number, or seed value,
produces exactly the same sequence of digits.
One way to do better is to vary the seed value randomly.
Noll and his colleagues decided that the unpredictably wandering globs in a
Lava Lite lamp, operated according to the manufacturer’s instructions, are a
more convenient source of randomness than, say, the sporadic decays of a
radioactive element.
"While any good chaotic source could be used, we favor
Lava Lite lamps in part because they were the source of inspiration for Lavarand
and in part because they are cool," the researchers admit.
A digital camera periodically photographs a set of six Lava
Lite lamps, each one generally in a different stage of activity. The camera
adds its own electronic noise to the data, and the resulting image is
converted into a string of 1s and 0s. That string is then mathematically
manipulated according to a scheme known as the National Institute of Standards
and Technology’s Secure Hash Algorithm, which compresses and scrambles the
921,600 bytes of the original image into a 140-byte packet of digits. This
packet then serves as the seed value for a computer-based random-number
generator. Each such value starts a chain of mathematical operations that
produces a different string of apparently random digits.
In one application, Lavarand serves as the random number
generator driving a system for creating haiku. It also provides lottery
numbers.
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