317:
long enough during boot to ensure sufficient entropy exists. Embedded devices often lack rotating disk drives, human interface devices, and even fans, and the network interface, if any, will not have been active for long enough to provide much entropy. Lacking easy access to entropy, some devices may use hard-coded keys to seed random generators, or seed random generators from easily guessed unique identifiers such as the device's MAC address. A simple study demonstrated the widespread use of weak keys by finding many embedded systems such as routers using the same keys. It was thought that the number of weak keys found would have been far higher if simple and often attacker determinable one-time unique identifiers had not been incorporated into the entropy of some of these systems.
260:
102:
has integrated cryptography as one of its main goals and has always worked on increasing its entropy for encryption but also for randomising many parts of the OS, including various internal operations of its kernel. Around 2011, two of the random devices were dropped and linked into a single source
316:
have difficulty gathering enough entropy as they are often very simple devices with short boot times, and key generation operations that require sufficient entropy are often one of the first things a system may do. Common entropy sources may not exist on these devices, or will not have been active
38:
collected by an operating system or application for use in cryptography or other uses that require random data. This randomness is often collected from hardware sources (variance in fan noise or HDD), either pre-existing ones such as mouse movements or specially provided randomness generators. A
417:
utilising the Linux kernel, or any other kernel or userspace process that generates entropy from the console and the storage subsystem, is often less than ideal because of the lack of a mouse and keyboard, thus servers have to generate their entropy from a limited set of resources such as IDE
73:, allows audio data to be used as an entropy source. Also available are video_entropyd, which calculates random data from a video-source and entropybroker, which includes these three and can be used to distribute the entropy data to systems not capable of running any of these (e.g.
180:
applications running on the
Windows platform use other measures to get randomness. For example, GnuPG, as of version 1.06, uses a variety of sources such as the number of free bytes in memory that combined with a random seed generates desired randomness it needs.
103:
as it could produce hundreds of megabytes per second of high quality random data on an average system. This made depletion of random data by userland programs impossible on OpenBSD once enough entropy has initially been gathered.
1016:
127:
since
Solaris 2.6, and have been a standard feature since Solaris 9. As of Solaris 10, administrators can remove existing entropy sources or define new ones via the kernel-level cryptographic framework.
508:
For Unix/BSD derivatives there exists a USB based solution that utilizes an ARM Cortex CPU for filtering / securing the bit stream generated by two entropy generator sources in the system.
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On servers with low entropy, a process can appear hung when it is waiting for random characters to appear in /dev/random (on Linux-based systems). For example, there was a known problem in
1423:
349:
There are some software packages that allow one to use a userspace process to gather random characters, exactly what /dev/random does, such as EGD, the
Entropy Gathering Daemon.
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493:
Commonly used entropy sources include the mouse, keyboard, and IDE timings, but there are other potential sources. For example, one could collect entropy from the computer's
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There are some Linux kernel patches allowing one to use more entropy sources. The audio_entropyd project, which is included in some operating systems such as
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movements, and integrated drive electronics (IDE) timings and makes the random character data available to other operating system processes through the
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and hardware often feature integrated generators that can provide high-quality and high-speed entropy to operating systems. On systems based on the
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413:, especially those supervising Internet servers, have to ensure that the server processes will not halt because of entropy depletion. Entropy on
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473:: If a server fails to use a proper source of randomness, the keys generated by the server will be insecure. In some cases a
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There are some companies manufacturing entropy generation devices, and some of them are shipped with drivers for Linux.
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keys often, and this may in some cases help a server to continue functioning normally even with an entropy bottleneck.
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329:(TRNG) can be a (de)central service. One example of a centralized system where a random number can be acquired is the
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A 3rd-party kernel module implementing /dev/random is also available for releases dating back to
Solaris 2.4.
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1363:"[gnutls-dev] gnutls_rsa_params_init hangs. Is regenerating rsa-params once a day too frequent?"
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as a substitute for /dev/random as this may cause SSL/TLS connections to have lower-grade encryption.
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and higher. New API is called
Cryptography API: Next Generation (CNG). Windows's CNG uses the binary
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and should generally be at least 2000 bits (out of a maximum of 4096). Entropy changes frequently.
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to pool entropy. In some systems, network interrupts can be used as an entropy source as well.
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Administrators responsible for systems that have low or zero entropy should not attempt to use
1244:"Linux support for random number generator in i8xx chipsets — The Linux Kernel documentation"
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52:
1424:"Build your own cryptographically safe server/client protocol - 4.8.3. Collecting entropy"
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695:"Entropy and Random Devices | LinuxLink by TimeSys – Your Embedded Linux Resource"
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123:/dev/random and /dev/urandom have been available as Sun packages or patches for
1009:"Millions of embedded devices use the same hard-coded SSH and TLS private keys"
440:
338:
185:
1314:"'SSL/TLS entropy problem, aka pops timeouts (was: sasl ldap problem)' - MARC"
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485:(PRNG), and this happens when not enough entropy is introduced into the PRNG.
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and /dev/urandom. This capability was introduced in Linux version 1.3.30.
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On Linux system, one can install the rng-tools package that supports the
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lack of entropy can have a negative impact on performance and security.
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Newer version of
Windows are able to use a variety of entropy sources:
35:
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to gather entropy in a similar fashion to Linux kernel's /dev/random.
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A driver ported from the Linux kernel has been made available for the
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27:
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337:. The Cardano platform uses the participants of their decentralized
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848:"Source for entropy on Windows platforms with CryptoAPI installed"
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Unix entropy source can be used for keystroke timing attacks
878:"How does Windows GnuPG generate random numbers on keygen?"
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HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Cryptography\RNG\Seed
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Entropy sources can be used for keyboard timing attacks.
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Programmers using CAPI can get entropy by calling CAPI's
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to store a seeded value from all of its entropy sources.
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that allows software processes to retrieve random data.
1513:
Overview of entropy and of entropy generators in Linux
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1404:
Re: entropy depletion (was: SSL/TLS passive sniffing)
1343:[TLS] Re: Short Ephermal Diffie-Hellman keys
736:
734:
63:
983:"CryptGenRandom function (Wincrypt.h) - Win32 apps"
958:"UEFI entropy gathering protocol - Windows drivers"
731:
1519:
1443:: CS1 maint: bot: original URL status unknown (
822:"GPL command-line shred alternative for Windows"
1200:http://random.com.hr/products/random/hg324.html
352:
335:National Institute of Standards and Technology
281:. There might be a discussion about this on
576:"Robotic Tendencies » Missing entropy"
1426:. Archived from the original on 2012-07-23
619:"Fedora Package Database – audio-entropyd"
320:
1266:"Re: [exim] no reply to STARTTLS"
904:"[or-cvs] Get entropy in windows"
497:, or by building a sensor to measure the
405:
301:Learn how and when to remove this message
1481:"Randomness 101: LavaRand in Production"
875:
819:
792:"Rexx Entropy Gathering Daemon for OS/2"
1097:"'Re: SSL/TLS entropy problem,' - MARC"
742:"Solaris /dev/random through emulation"
454:to hang in some cases because of this.
402:that have no other sources of entropy.
213:if available and enabled on motherboard
1520:
1006:
884:from the original on December 1, 2021
828:from the original on October 27, 2021
427:/proc/sys/kernel/random/entropy_avail
375:(TRNGs) found in CPUs supporting the
341:protocol to generate random numbers.
1038:"A solution for scalable randomness"
876:Malayter, Ryan (February 15, 2002).
675:from the original on 27 October 2012
518:as an additional source of entropy.
514:use an image feed from a rack of 80
488:
477:(malicious attacker) can guess some
253:
245:Keyboard timings and Mouse movements
188:(), after properly initializing it.
161:Windows's CryptoAPI uses the binary
1048:from the original on April 17, 2021
1030:
820:Malayter, Ryan (November 9, 2001).
719:/dev/{,u}random driver for GNU/Hurd
669:"haveged – A simple entropy daemon"
439:Some software systems change their
249:
154:releases newer than Windows 95 use
13:
1369:. 14 December 2004. Archived from
1254:from the original on 31 July 2013.
201:HKEY_LOCAL_MACHINE\SYSTEM\RNG\Seed
14:
1539:
1506:
88:
1491:from the original on May 1, 2023
635:. March 23, 2021. Archived from
603:. March 23, 2021. Archived from
481:of entropy from the output of a
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139:There is a software package for
77:). Furthermore, one can use the
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1324:from the original on 2018-11-15
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1276:from the original on 2012-07-22
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1225:from the original on 2007-10-21
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802:from the original on 2007-10-31
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748:from the original on 2007-11-04
582:from the original on 2022-12-06
220:interface (if booted from UEFI)
42:
1528:Pseudorandom number generators
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661:
653:. May 29, 2020. Archived from
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611:
593:
568:
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191:CryptoAPI was deprecated from
106:
1:
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483:pseudorandom number generator
425:is viewable through the file
373:true random number generators
178:free and open source software
528:Entropy (information theory)
327:true random number generator
226:CPU instruction if available
7:
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353:Hardware-originated entropy
10:
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556:random(4) - Linux man page
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18:
421:The entropy pool size in
331:randomness beacon service
203:to store a seeded value.
95:OpenBSD security features
1294:random(4) Linux man page
933:"About CNG - Win32 apps"
381:Trusted Platform Modules
21:Entropy (disambiguation)
1352:(ietf.org mailing list)
465:Entropy can affect the
321:(De)centralized systems
236:OEM0 ACPI table content
229:Hardware system clock (
134:
51:generates entropy from
1176:"Random Noise Sources"
601:"audio entropy daemon"
406:Practical implications
767:"Solaris /dev/random"
411:System administrators
172:Because CryptoAPI is
1487:. November 6, 2017.
1463:www.entropykey.co.uk
1151:"Re: /dev/hw_random"
1126:"Re: /dev/hw_random"
1007:Constantin, Lucian.
852:www.mail-archive.com
271:confusing or unclear
19:For other uses, see
1485:The Cloudflare Blog
279:clarify the section
1409:2011-05-17 at the
1390:2011-07-19 at the
1383:Zalewski, Michal;
1348:2007-11-11 at the
1341:Josefsson, Simon;
1299:2007-10-11 at the
1205:2008-05-13 at the
724:2007-09-18 at the
561:2007-10-11 at the
81:algorithm through
1469:on July 22, 2010.
908:archives.seul.org
489:Potential sources
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152:Microsoft Windows
16:Computing concept
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1128:. Archived from
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1068:"Random Numbers"
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651:"Entropy Broker"
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75:virtual machines
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216:Entropy from
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193:Windows Vista
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61:special files
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1493:. Retrieved
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1467:the original
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1428:. Retrieved
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1371:the original
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1326:. Retrieved
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1278:. Retrieved
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1328:2023-05-23
1280:2023-05-23
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888:May 23,
832:May 23,
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