Random Number Generation

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2024-05-15 16:00:04

Random numbers are important in a number of cryptographic applications, and by random I mean unpredictable in a very strict sense. The following describes a random number generator based on an unpredictable physical phenomenon. One method of generating unpredictable numbers is to measure the time intervals between decay events of a radioactive substance.

One method of generating unpredictable numbers is to measure the time intervals between decay events of a radioactive substance.

One common and inexpensive radioactive substance is Americium 241, found in household ionizing smoke detectors. Americium 241 is a relatively soft radioactive metal with a half-life of 432.6 years. An average consumer smoke detector contains about 0.3 micrograms of Americium 241 in the form of americium dioxide. It decays to Neptunium-237 by emitting an alpha particle, with a by-product (about one percent of the emitted energy) of gamma rays. This decay is unpredicable, so if we have a way of counting and measuring this decay we can convert those data into random numbers. In my set-up I use a First Alert model SA301B battery-operated smoke detector, basically because it was handy. Please use a detector that is not needed to protect a dwelling. They're pretty cheap and no-name brands are available at Home Depot or other home improvement stores for well under $10. Note that the ionizing smoke detector contains radioactive material, not the photoelectric ones (unless they are the expensive dual-method detectors). The radioactive ones are easy to spot because they have unusual warnings on the label, as seen here.

Americium 241 is a relatively soft radioactive metal with a half-life of 432.6 years. An average consumer smoke detector contains about 0.3 micrograms of Americium 241 in the form of americium dioxide. It decays to Neptunium-237 by emitting an alpha particle, with a by-product (about one percent of the emitted energy) of gamma rays. This decay is unpredicable, so if we have a way of counting and measuring this decay we can convert those data into random numbers.