1Introduction: 2 3 The hw_random framework is software that makes use of a 4 special hardware feature on your CPU or motherboard, 5 a Random Number Generator (RNG). The software has two parts: 6 a core providing the /dev/hw_random character device and its 7 sysfs support, plus a hardware-specific driver that plugs 8 into that core. 9 10 To make the most effective use of these mechanisms, you 11 should download the support software as well. Download the 12 latest version of the "rng-tools" package from the 13 hw_random driver's official Web site: 14 15 http://sourceforge.net/projects/gkernel/ 16 17 Those tools use /dev/hw_random to fill the kernel entropy pool, 18 which is used internally and exported by the /dev/urandom and 19 /dev/random special files. 20 21Theory of operation: 22 23 CHARACTER DEVICE. Using the standard open() 24 and read() system calls, you can read random data from 25 the hardware RNG device. This data is NOT CHECKED by any 26 fitness tests, and could potentially be bogus (if the 27 hardware is faulty or has been tampered with). Data is only 28 output if the hardware "has-data" flag is set, but nevertheless 29 a security-conscious person would run fitness tests on the 30 data before assuming it is truly random. 31 32 The rng-tools package uses such tests in "rngd", and lets you 33 run them by hand with a "rngtest" utility. 34 35 /dev/hw_random is char device major 10, minor 183. 36 37 CLASS DEVICE. There is a /sys/class/misc/hw_random node with 38 two unique attributes, "rng_available" and "rng_current". The 39 "rng_available" attribute lists the hardware-specific drivers 40 available, while "rng_current" lists the one which is currently 41 connected to /dev/hw_random. If your system has more than one 42 RNG available, you may change the one used by writing a name from 43 the list in "rng_available" into "rng_current". 44 45========================================================================== 46 47 Hardware driver for Intel/AMD/VIA Random Number Generators (RNG) 48 Copyright 2000,2001 Jeff Garzik <jgarzik@pobox.com> 49 Copyright 2000,2001 Philipp Rumpf <prumpf@mandrakesoft.com> 50 51 52About the Intel RNG hardware, from the firmware hub datasheet: 53 54 The Firmware Hub integrates a Random Number Generator (RNG) 55 using thermal noise generated from inherently random quantum 56 mechanical properties of silicon. When not generating new random 57 bits the RNG circuitry will enter a low power state. Intel will 58 provide a binary software driver to give third party software 59 access to our RNG for use as a security feature. At this time, 60 the RNG is only to be used with a system in an OS-present state. 61 62Intel RNG Driver notes: 63 64 * FIXME: support poll(2) 65 66 NOTE: request_mem_region was removed, for three reasons: 67 1) Only one RNG is supported by this driver, 2) The location 68 used by the RNG is a fixed location in MMIO-addressable memory, 69 3) users with properly working BIOS e820 handling will always 70 have the region in which the RNG is located reserved, so 71 request_mem_region calls always fail for proper setups. 72 However, for people who use mem=XX, BIOS e820 information is 73 -not- in /proc/iomem, and request_mem_region(RNG_ADDR) can 74 succeed. 75 76Driver details: 77 78 Based on: 79 Intel 82802AB/82802AC Firmware Hub (FWH) Datasheet 80 May 1999 Order Number: 290658-002 R 81 82 Intel 82802 Firmware Hub: Random Number Generator 83 Programmer's Reference Manual 84 December 1999 Order Number: 298029-001 R 85 86 Intel 82802 Firmware HUB Random Number Generator Driver 87 Copyright (c) 2000 Matt Sottek <msottek@quiknet.com> 88 89 Special thanks to Matt Sottek. I did the "guts", he 90 did the "brains" and all the testing. 91