Lavarand was Silicon Graphics' name for its hardware random number generator that worked by taking pictures of the patterns made by the floating material in lava lamps, extracting random data from the pictures, and using the result to seed a pseudo-random number generator.[1] Although the secondary part of the random number generation uses a pseudo-random number generator, the full process essentially qualifies as a "true" random number generator due to the random seed that is used.
It is covered under U.S. Patent 5,732,138, titled "Method for seeding a pseudo-random number generator with a cryptographic hash of a digitization of a chaotic system."
From 1997 through 2001,[2] there was a web site at http://lavarand.sgi.com/ demonstrating the technique. Landon Curt Noll, one of the originators, went on to help develop LavaRnd, which does not use lava lamps. Despite the short life of lavarand.sgi.com, it is often cited as an example of an online random number source.[3][4]