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Diffstat (limited to 'kernel/Documentation/hw_random.txt')
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diff --git a/kernel/Documentation/hw_random.txt b/kernel/Documentation/hw_random.txt new file mode 100644 index 000000000..026e237bb --- /dev/null +++ b/kernel/Documentation/hw_random.txt @@ -0,0 +1,90 @@ +Introduction: + + The hw_random framework is software that makes use of a + special hardware feature on your CPU or motherboard, + a Random Number Generator (RNG). The software has two parts: + a core providing the /dev/hw_random character device and its + sysfs support, plus a hardware-specific driver that plugs + into that core. + + To make the most effective use of these mechanisms, you + should download the support software as well. Download the + latest version of the "rng-tools" package from the + hw_random driver's official Web site: + + http://sourceforge.net/projects/gkernel/ + + Those tools use /dev/hw_random to fill the kernel entropy pool, + which is used internally and exported by the /dev/urandom and + /dev/random special files. + +Theory of operation: + + CHARACTER DEVICE. Using the standard open() + and read() system calls, you can read random data from + the hardware RNG device. This data is NOT CHECKED by any + fitness tests, and could potentially be bogus (if the + hardware is faulty or has been tampered with). Data is only + output if the hardware "has-data" flag is set, but nevertheless + a security-conscious person would run fitness tests on the + data before assuming it is truly random. + + The rng-tools package uses such tests in "rngd", and lets you + run them by hand with a "rngtest" utility. + + /dev/hw_random is char device major 10, minor 183. + + CLASS DEVICE. There is a /sys/class/misc/hw_random node with + two unique attributes, "rng_available" and "rng_current". The + "rng_available" attribute lists the hardware-specific drivers + available, while "rng_current" lists the one which is currently + connected to /dev/hw_random. If your system has more than one + RNG available, you may change the one used by writing a name from + the list in "rng_available" into "rng_current". + +========================================================================== + + Hardware driver for Intel/AMD/VIA Random Number Generators (RNG) + Copyright 2000,2001 Jeff Garzik <jgarzik@pobox.com> + Copyright 2000,2001 Philipp Rumpf <prumpf@mandrakesoft.com> + + +About the Intel RNG hardware, from the firmware hub datasheet: + + The Firmware Hub integrates a Random Number Generator (RNG) + using thermal noise generated from inherently random quantum + mechanical properties of silicon. When not generating new random + bits the RNG circuitry will enter a low power state. Intel will + provide a binary software driver to give third party software + access to our RNG for use as a security feature. At this time, + the RNG is only to be used with a system in an OS-present state. + +Intel RNG Driver notes: + + * FIXME: support poll(2) + + NOTE: request_mem_region was removed, for three reasons: + 1) Only one RNG is supported by this driver, 2) The location + used by the RNG is a fixed location in MMIO-addressable memory, + 3) users with properly working BIOS e820 handling will always + have the region in which the RNG is located reserved, so + request_mem_region calls always fail for proper setups. + However, for people who use mem=XX, BIOS e820 information is + -not- in /proc/iomem, and request_mem_region(RNG_ADDR) can + succeed. + +Driver details: + + Based on: + Intel 82802AB/82802AC Firmware Hub (FWH) Datasheet + May 1999 Order Number: 290658-002 R + + Intel 82802 Firmware Hub: Random Number Generator + Programmer's Reference Manual + December 1999 Order Number: 298029-001 R + + Intel 82802 Firmware HUB Random Number Generator Driver + Copyright (c) 2000 Matt Sottek <msottek@quiknet.com> + + Special thanks to Matt Sottek. I did the "guts", he + did the "brains" and all the testing. |