This page lists online resources for collecting and processing crypto-strength randomness. See this paper for a motivating example of why this is important to get right.

Writings on randomness

• Carl Ellison's excellent document on generating randomness
• RFC 4086: randomness recommendations
• RSA's intro to software random number generation
• Don Mitchell's suggestions for generating randomness
• Paul Kocher describes a subtle bug in RSAREF's randomness routines, which you should avoid if you ever write any randomness code.
• Don Davis describes a technique for mining entropy from your disk drive, and a subsequent post from him on portably extracting disk entropy by timing memory paging effects.
• Don Davis writes about pitfalls in using mouse events for randomness; see also a followup from J. Gallegos on more pitfalls with finding randomness from mice.
• Stephan Neuhaus analyzes the randomness of session keys in PGP: worthwhile reading!
• Arnold Reinhold explains how to generate high-quality true randomness by hand and surveys PGP passphrase entropy
• The passphrase FAQ
• An overview from Finland
• The physics of Geiger counters
• A fast quantum random generator: using quantum mechanics to build fast hardware for generating randomness
• David Honig argues "The FreeBSD /dev/random entropy-count calculation is probably too generous"; see also this page
• Chow and Herzberg propose a Network randomization protocol
• Terry Ritter's very extensive archive of Usenet posts on true randomness
• John Denker's design of a hardware random number generator

Source code for generating randomness

• A Yarrow implementation from Zero Knowledge Systems
• Wei Dai's code snippet for generating randomness on Windows 2000/NT using CryptoAPI
• Theodore Ts'o's Linux /dev/random source, part of the Linux 1.3.x kernel
• A Linux kernel patch for extracting entropy from the Intel 82802 hardware RNG
• Video entropyd
• John Denker's random number generation code
• Jack Lacy's CryptoLib, with a great random number generator: send email for more info
• librand, a random number package based on event interval variations, from Matt Blaze, Jack Lacy, and Don Mitchell; old version available here
• R. Walking-Owl's NOISE.SYS, for generating crypto-quality randomness under DOS [home page]
• Carl Ellison's software for mixing entropy
• Marcus J. Ranum's nifty source for a randomness driver
• Damien Miller's audio-entropyd, a daemon for harvesting randomness by sampling your soundcard
• Several randomness-generating programs
• Netscape's randomness fix
• A Java true random number class, based on librand above; untested [a simplified version]
• GenRand, a Java random number class
• Audio-based randomness
• An undocumented command-line switch to generate random bytes with PGP; but beware: PGP guru Galactus reports that the undocumented feature is bug-ridden; thanks to S for the tip
• A random passphrase generator in Javascript
• Don Davis on Solaris cryptorand
• The EntropyPool system (in Java)

Source code for testing randomness

• George Marsaglia's DIEHARD tests
• Bob Jenkin's randomness tests; and a local copy of one of them
• More randomness tests from Stephan Neuhaus; read his paper first
• Noise sphere implementations: [for PCs, in C] [for X11, in C] [Java version]
• Also see Terry Ritter's very extensive archive of Usenet posts on testing randomness
• David Honig's C implementation of Maurer's test

Hardware for generating randomness

• Cryptography Research's evaluation of the hardware RNG in the C3 CPU
• Cryptography Research's evaluation of the hardware RNG in the Intel CPU
• Reinhold's excellent list of hardware randomness sources
• External hardware for true random number generation
• Hardware for generating true randomness, using quantum mechanics (!), from Univ. of Geneva, Switzerland
• Aware Electronics
• Robert Davies closely examines several hardware RNG devices for a lottery (now that's a demanding application!). His careful analysis is definitely worth reading, and he points out some surprising pitfalls.
• Hotbits, with a description of how they generate true randomness via radioactive decay.
• Plans for a hardware RNG device in Cryptosystems Journal (see volume 2); Maurice Onraet reports success with the kit.
• Tundra Corp.'s RPG 1210
• The SG100 [also available: a simple security analysis]
• ORB: open random bit generator
• Z5000 true random number generator
• A newsgroup article listing some RNG's (and their bitrates)
• Plans for another simple hardware RNG device
• Will Ware's plans for building a hardware RNG
• Interesting idea for hobbyists: using a smoke alarm as a RNG

Source code to other useful crypto modules

• MD5
• SHA
• Several crypto libraries
• Peter Gutmann's crypto library (see especially his lib_rand.c) [old version]
• Jack Lacy's CryptoLib, with a great random number generator: send email for more info
• Online version of the Applied Cryptography disk
• SSLeay FAQ
• My local crypto hotlist

Miscellaneous

• An excellent list of links on crypto-quality randomness
• Diceware: manual entropy generation
• lavarand: generating randomness with lava lamps (!)
• Extensive links on random number generation (both cryptographic and non-cryptographic)