1========================================================== 2Linux support for random number generator in i8xx chipsets 3========================================================== 4 5Introduction 6============ 7 8The hw_random framework is software that makes use of a 9special hardware feature on your CPU or motherboard, 10a Random Number Generator (RNG). The software has two parts: 11a core providing the /dev/hwrng character device and its 12sysfs support, plus a hardware-specific driver that plugs 13into that core. 14 15To make the most effective use of these mechanisms, you 16should download the support software as well. Download the 17latest version of the "rng-tools" package from the 18hw_random driver's official Web site: 19 20 http://sourceforge.net/projects/gkernel/ 21 22Those tools use /dev/hwrng to fill the kernel entropy pool, 23which is used internally and exported by the /dev/urandom and 24/dev/random special files. 25 26Theory of operation 27=================== 28 29CHARACTER DEVICE. Using the standard open() 30and read() system calls, you can read random data from 31the hardware RNG device. This data is NOT CHECKED by any 32fitness tests, and could potentially be bogus (if the 33hardware is faulty or has been tampered with). Data is only 34output if the hardware "has-data" flag is set, but nevertheless 35a security-conscious person would run fitness tests on the 36data before assuming it is truly random. 37 38The rng-tools package uses such tests in "rngd", and lets you 39run them by hand with a "rngtest" utility. 40 41/dev/hwrng is char device major 10, minor 183. 42 43CLASS DEVICE. There is a /sys/class/misc/hw_random node with 44two unique attributes, "rng_available" and "rng_current". The 45"rng_available" attribute lists the hardware-specific drivers 46available, while "rng_current" lists the one which is currently 47connected to /dev/hwrng. If your system has more than one 48RNG available, you may change the one used by writing a name from 49the list in "rng_available" into "rng_current". 50 51========================================================================== 52 53 54Hardware driver for Intel/AMD/VIA Random Number Generators (RNG) 55 - Copyright 2000,2001 Jeff Garzik <jgarzik@pobox.com> 56 - Copyright 2000,2001 Philipp Rumpf <prumpf@mandrakesoft.com> 57 58 59About the Intel RNG hardware, from the firmware hub datasheet 60============================================================= 61 62The Firmware Hub integrates a Random Number Generator (RNG) 63using thermal noise generated from inherently random quantum 64mechanical properties of silicon. When not generating new random 65bits the RNG circuitry will enter a low power state. Intel will 66provide a binary software driver to give third party software 67access to our RNG for use as a security feature. At this time, 68the RNG is only to be used with a system in an OS-present state. 69 70Intel RNG Driver notes 71====================== 72 73FIXME: support poll(2) 74 75.. note:: 76 77 request_mem_region was removed, for three reasons: 78 79 1) Only one RNG is supported by this driver; 80 2) The location used by the RNG is a fixed location in 81 MMIO-addressable memory; 82 3) users with properly working BIOS e820 handling will always 83 have the region in which the RNG is located reserved, so 84 request_mem_region calls always fail for proper setups. 85 However, for people who use mem=XX, BIOS e820 information is 86 **not** in /proc/iomem, and request_mem_region(RNG_ADDR) can 87 succeed. 88 89Driver details 90============== 91 92Based on: 93 Intel 82802AB/82802AC Firmware Hub (FWH) Datasheet 94 May 1999 Order Number: 290658-002 R 95 96Intel 82802 Firmware Hub: 97 Random Number Generator 98 Programmer's Reference Manual 99 December 1999 Order Number: 298029-001 R 100 101Intel 82802 Firmware HUB Random Number Generator Driver 102 Copyright (c) 2000 Matt Sottek <msottek@quiknet.com> 103 104Special thanks to Matt Sottek. I did the "guts", he 105did the "brains" and all the testing. 106