1 ================================= 1 =================================
2 Hardware random number generators 2 Hardware random number generators
3 ================================= 3 =================================
4 4
5 Introduction 5 Introduction
6 ============ 6 ============
7 7
8 The hw_random framework is software that makes 8 The hw_random framework is software that makes use of a
9 special hardware feature on your CPU or mother 9 special hardware feature on your CPU or motherboard,
10 a Random Number Generator (RNG). The software 10 a Random Number Generator (RNG). The software has two parts:
11 a core providing the /dev/hwrng character devi 11 a core providing the /dev/hwrng character device and its
12 sysfs support, plus a hardware-specific driver 12 sysfs support, plus a hardware-specific driver that plugs
13 into that core. 13 into that core.
14 14
15 To make the most effective use of these mechan 15 To make the most effective use of these mechanisms, you
16 should download the support software as well. 16 should download the support software as well. Download the
17 latest version of the "rng-tools" package from 17 latest version of the "rng-tools" package from:
18 18
19 https://github.com/nhorman/rng-tools 19 https://github.com/nhorman/rng-tools
20 20
21 Those tools use /dev/hwrng to fill the kernel 21 Those tools use /dev/hwrng to fill the kernel entropy pool,
22 which is used internally and exported by the / 22 which is used internally and exported by the /dev/urandom and
23 /dev/random special files. 23 /dev/random special files.
24 24
25 Theory of operation 25 Theory of operation
26 =================== 26 ===================
27 27
28 CHARACTER DEVICE. Using the standard open() 28 CHARACTER DEVICE. Using the standard open()
29 and read() system calls, you can read random d 29 and read() system calls, you can read random data from
30 the hardware RNG device. This data is NOT CHE 30 the hardware RNG device. This data is NOT CHECKED by any
31 fitness tests, and could potentially be bogus 31 fitness tests, and could potentially be bogus (if the
32 hardware is faulty or has been tampered with). 32 hardware is faulty or has been tampered with). Data is only
33 output if the hardware "has-data" flag is set, 33 output if the hardware "has-data" flag is set, but nevertheless
34 a security-conscious person would run fitness 34 a security-conscious person would run fitness tests on the
35 data before assuming it is truly random. 35 data before assuming it is truly random.
36 36
37 The rng-tools package uses such tests in "rngd 37 The rng-tools package uses such tests in "rngd", and lets you
38 run them by hand with a "rngtest" utility. 38 run them by hand with a "rngtest" utility.
39 39
40 /dev/hwrng is char device major 10, minor 183. 40 /dev/hwrng is char device major 10, minor 183.
41 41
42 CLASS DEVICE. There is a /sys/class/misc/hw_r 42 CLASS DEVICE. There is a /sys/class/misc/hw_random node with
43 two unique attributes, "rng_available" and "rn 43 two unique attributes, "rng_available" and "rng_current". The
44 "rng_available" attribute lists the hardware-s 44 "rng_available" attribute lists the hardware-specific drivers
45 available, while "rng_current" lists the one w 45 available, while "rng_current" lists the one which is currently
46 connected to /dev/hwrng. If your system has m 46 connected to /dev/hwrng. If your system has more than one
47 RNG available, you may change the one used by 47 RNG available, you may change the one used by writing a name from
48 the list in "rng_available" into "rng_current" 48 the list in "rng_available" into "rng_current".
49 49
50 ============================================== 50 ==========================================================================
51 51
52 52
53 Hardware driver for Intel/AMD/VIA Random Numbe 53 Hardware driver for Intel/AMD/VIA Random Number Generators (RNG)
54 - Copyright 2000,2001 Jeff Garzik <jgar 54 - Copyright 2000,2001 Jeff Garzik <jgarzik@pobox.com>
55 - Copyright 2000,2001 Philipp Rumpf <pr 55 - Copyright 2000,2001 Philipp Rumpf <prumpf@mandrakesoft.com>
56 56
57 57
58 About the Intel RNG hardware, from the firmwar 58 About the Intel RNG hardware, from the firmware hub datasheet
59 ============================================== 59 =============================================================
60 60
61 The Firmware Hub integrates a Random Number Ge 61 The Firmware Hub integrates a Random Number Generator (RNG)
62 using thermal noise generated from inherently 62 using thermal noise generated from inherently random quantum
63 mechanical properties of silicon. When not gen 63 mechanical properties of silicon. When not generating new random
64 bits the RNG circuitry will enter a low power 64 bits the RNG circuitry will enter a low power state. Intel will
65 provide a binary software driver to give third 65 provide a binary software driver to give third party software
66 access to our RNG for use as a security featur 66 access to our RNG for use as a security feature. At this time,
67 the RNG is only to be used with a system in an 67 the RNG is only to be used with a system in an OS-present state.
68 68
69 Intel RNG Driver notes 69 Intel RNG Driver notes
70 ====================== 70 ======================
71 71
72 FIXME: support poll(2) 72 FIXME: support poll(2)
73 73
74 .. note:: 74 .. note::
75 75
76 request_mem_region was removed, for th 76 request_mem_region was removed, for three reasons:
77 77
78 1) Only one RNG is supported by this d 78 1) Only one RNG is supported by this driver;
79 2) The location used by the RNG is a f 79 2) The location used by the RNG is a fixed location in
80 MMIO-addressable memory; 80 MMIO-addressable memory;
81 3) users with properly working BIOS e8 81 3) users with properly working BIOS e820 handling will always
82 have the region in which the RNG is 82 have the region in which the RNG is located reserved, so
83 request_mem_region calls always fai 83 request_mem_region calls always fail for proper setups.
84 However, for people who use mem=XX, 84 However, for people who use mem=XX, BIOS e820 information is
85 **not** in /proc/iomem, and request 85 **not** in /proc/iomem, and request_mem_region(RNG_ADDR) can
86 succeed. 86 succeed.
87 87
88 Driver details 88 Driver details
89 ============== 89 ==============
90 90
91 Based on: 91 Based on:
92 Intel 82802AB/82802AC Firmware Hub (FW 92 Intel 82802AB/82802AC Firmware Hub (FWH) Datasheet
93 May 1999 Order Number: 290658-002 R 93 May 1999 Order Number: 290658-002 R
94 94
95 Intel 82802 Firmware Hub: 95 Intel 82802 Firmware Hub:
96 Random Number Generator 96 Random Number Generator
97 Programmer's Reference Manual 97 Programmer's Reference Manual
98 December 1999 Order Number: 298029-001 98 December 1999 Order Number: 298029-001 R
99 99
100 Intel 82802 Firmware HUB Random Number Generat 100 Intel 82802 Firmware HUB Random Number Generator Driver
101 Copyright (c) 2000 Matt Sottek <msottek 101 Copyright (c) 2000 Matt Sottek <msottek@quiknet.com>
102 102
103 Special thanks to Matt Sottek. I did the "gut 103 Special thanks to Matt Sottek. I did the "guts", he
104 did the "brains" and all the testing. 104 did the "brains" and all the testing.
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