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Based on kernel version 4.16.1. Page generated on 2018-04-09 11:53 EST.

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