Root/
1 | Introduction: |
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 | |
21 | Theory 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 | |
52 | About 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 | |
62 | Intel RNG Driver notes: |
63 | |
64 | * FIXME: support poll(2) |
65 | |
66 | NOTE: request_mem_region was removed, for two 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 | |
76 | Driver 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 |
Branches:
ben-wpan
ben-wpan-stefan
javiroman/ks7010
jz-2.6.34
jz-2.6.34-rc5
jz-2.6.34-rc6
jz-2.6.34-rc7
jz-2.6.35
jz-2.6.36
jz-2.6.37
jz-2.6.38
jz-2.6.39
jz-3.0
jz-3.1
jz-3.11
jz-3.12
jz-3.13
jz-3.15
jz-3.16
jz-3.18-dt
jz-3.2
jz-3.3
jz-3.4
jz-3.5
jz-3.6
jz-3.6-rc2-pwm
jz-3.9
jz-3.9-clk
jz-3.9-rc8
jz47xx
jz47xx-2.6.38
master
Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9