As of 00:00 UTC on January 1, 2023 the Fourmilab HotBits radioactive random number generator has been retired. All requests for radioactively-generated random numbers with API keys beginning with “HB” will be rejected with an error message directing the requester to a page announcing the retirement.
Since May 1996, Fourmilab made HotBits available for free on the Web to all who wanted them, subject only to a daily quota to avoid exhausting the limited capacity of the generator machines and, later, an API key to defend the site against the denial of service attacks any resource on the Web inevitably attracts.
Migration of the Fourmilab site to cloud hosting on Amazon Web Services made it increasingly difficult to support HotBits, especially on the existing hardware, some of which is two decades old. Consequently, the existing radioactively-generated HotBits service was shut down at the end of 2022.
HotBits API key holders may continue to request data from a “secondary hardware random number” generator which uses the Intel CPU built-in RDSEED instruction to generate random data. To use the secondary generator, use the same API key you have been using, but with the initial “H” replaced by an “R”. Other than the source of the random data, requests using the secondary generator work exactly like those using the radioactive generator. You can, of course, continue to use the pseudorandom generator by specifying an API key of “Pseudorandom”. Pseudorandom requests are not subject to any quota limitations.
I have no direct knowledge of the internal operation of the Intel RDSEED generator and do not certify its suitability for any purpose. Access to it is provided purely as a convenience for users of HotBits who wish an alternative now that the radioactive generator has ceased operation. With the end of the radioactive HotBits service, the HotBits Web pages will remain accessible as an archive of the project and guide to those interested in setting up their own servers.
As of 2022-09-01, HotBits API keys have been issued only in the “RB1” form. These keys function only with the secondary generator and may continue to be used as before.
An earlier post on 2022-07-18 announced the process of the “Fourmilab HotBits Radioactive Random Number Generator Retirement” which has now been completed.