SherbyNet - /page/wikibook/entry.mu

Micron Document

<!DOCTYPE html>

<title>Entropy (computing)</title>

</head>

Entropy (computing)

</h1>

</header>

/* start https://en.wikipedia.org/ */

.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}

/* end https://en.wikipedia.org/ */

</style><div role="note" class="hatnote navigation-not-searchable">For other uses, see <a href="Entropy_(disambiguation)" class="mw-disambig" title="Entropy (disambiguation)">Entropy (disambiguation)</a>.</div>

In <a href="Computing" title="Computing">computing</a>, entropy is the <a href="Randomness" title="Randomness">randomness</a> 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 lack of entropy can have a negative impact on performance and security.

<div class="mw-heading mw-heading2"><h2 id="Linux_kernel">Linux kernel</h2></div>

The <a href="Linux_kernel" title="Linux kernel">Linux kernel</a> generates entropy from <a href="Keyboard_(computing)" class="mw-redirect" title="Keyboard (computing)">keyboard</a> timings, <a href="Mouse_(computing)" class="mw-redirect" title="Mouse (computing)">mouse</a> movements, and integrated drive electronics (IDE) timings and makes the random character data available to other operating system processes through the <a href="Special_file" class="mw-redirect" title="Special file">special files</a> <a href=".//dev/random" title="/dev/random">/dev/random</a> and /dev/urandom. This capability was introduced in Linux version 1.3.30.<a href="#cite_note-1">[1]</a>

There are some Linux kernel patches allowing one to use more entropy sources.<a href="#cite_note-2">[2]</a> The audio_entropyd project,<a href="#cite_note-3">[3]</a> which is included in some operating systems such as <a href="Fedora_(operating_system)" class="mw-redirect" title="Fedora (operating system)">Fedora</a>, allows audio data to be used as an entropy source.<a href="#cite_note-4">[4]</a> Also available are video_entropyd,<a href="#cite_note-5">[5]</a> which calculates random data from a video-source and entropybroker,<a href="#cite_note-6">[6]</a> which includes these three and can be used to distribute the entropy data to systems not capable of running any of these (e.g. <a href="Virtual_machines" class="mw-redirect" title="Virtual machines">virtual machines</a>). Furthermore, one can use the HAVEGE algorithm through haveged to pool entropy.<a href="#cite_note-7">[7]</a> In some systems, network interrupts can be used as an entropy source as well.<a href="#cite_note-8">[8]</a>

<div class="mw-heading mw-heading2"><h2 id="OpenBSD_kernel">OpenBSD kernel</h2></div>

<div role="note" class="hatnote navigation-not-searchable">Main article: <a href="OpenBSD_security_features" title="OpenBSD security features">OpenBSD security features</a></div>

<a href="OpenBSD" title="OpenBSD">OpenBSD</a> 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 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.

<div class="mw-heading mw-heading2"><h2 id="Hurd_kernel">Hurd kernel</h2></div>

A driver ported from the Linux kernel has been made available for the <a href="Hurd" class="mw-redirect" title="Hurd">Hurd</a> kernel.<a href="#cite_note-9">[9]</a>

<div class="mw-heading mw-heading2"><h2 id="Solaris">Solaris</h2></div>

/dev/random and /dev/urandom have been available as Sun packages or patches for <a href="Solaris_(operating_system)" class="mw-redirect" title="Solaris (operating system)">Solaris</a> since Solaris 2.6,<a href="#cite_note-Solaris_devrandom-10">[10]</a> and have been a standard feature since Solaris 9.<a href="#cite_note-11">[11]</a> As of Solaris 10, administrators can remove existing entropy sources or define new ones via the kernel-level cryptographic framework.

A 3rd-party kernel module implementing /dev/random is also available for releases dating back to Solaris 2.4.<a href="#cite_note-Solaris_devrandom-10">[10]</a>

There is a software package for <a href="OS/2" title="OS/2">OS/2</a> that allows software processes to retrieve random data.<a href="#cite_note-12">[12]</a>

<div class="mw-heading mw-heading2"><h2 id="Windows">Windows</h2></div>

<a href="Microsoft_Windows" title="Microsoft Windows">Microsoft Windows</a> releases newer than Windows 95 use <a href="Microsoft_CryptoAPI" title="Microsoft CryptoAPI">CryptoAPI</a> to gather entropy in a similar fashion to Linux kernel's /dev/random.<a href="#cite_note-13">[13]</a>

Windows's CryptoAPI uses the binary <a href="Windows_Registry" title="Windows Registry">registry</a> key HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Cryptography\RNG\Seed to store a seeded value from all of its entropy sources.<a href="#cite_note-14">[14]</a>

Because CryptoAPI is <a href="Closed-source" class="mw-redirect" title="Closed-source">closed-source</a>, some <a href="Free_and_open_source_software" class="mw-redirect" title="Free and open source software">free and open source software</a> 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.<a href="#cite_note-15">[15]</a>

Programmers using CAPI can get entropy by calling CAPI's <a href="CryptGenRandom" title="CryptGenRandom">CryptGenRandom</a>(), after properly initializing it.<a href="#cite_note-16">[16]</a>

CryptoAPI was deprecated from <a href="Windows_Vista" title="Windows Vista">Windows Vista</a> and higher. New API is called Cryptography API: Next Generation (CNG).<a href="#cite_note-17">[17]</a> Windows's CNG uses the binary <a href="Windows_Registry" title="Windows Registry">registry</a> key HKEY_LOCAL_MACHINE\SYSTEM\RNG\Seed to store a seeded value.

Newer version of Windows are able to use a variety of entropy sources:

<ul><li><a href="Trusted_Platform_Module" title="Trusted Platform Module">TPM</a> if available and enabled on motherboard</li>

<li>Entropy from <a href="UEFI" title="UEFI">UEFI</a> interface (if booted from UEFI)<a href="#cite_note-18">[18]</a></li>

<li><a href="RDRAND" title="RDRAND">RDRAND</a> CPU instruction if available</li>

<li>Hardware system clock (<a href="Real-time_clock" title="Real-time clock">RTC</a>)</li>

<li>OEM0 ACPI table content</li>

<li><a href="Interrupt" title="Interrupt">Interrupt</a> timings</li>

<li>Keyboard timings and Mouse movements<a href="#cite_note-19">[19]</a></li></ul>

<div class="mw-heading mw-heading2"><h2 id="Embedded_systems">Embedded systems</h2></div>

/* start https://en.wikipedia.org/ */

.mw-parser-output .ambox{border:1px solid #a2a9b1;border-left:10px solid #36c;background-color:#fbfbfb;box-sizing:border-box}.mw-parser-output .ambox+link+.ambox,.mw-parser-output .ambox+link+style+.ambox,.mw-parser-output .ambox+link+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+style+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+link+.ambox{margin-top:-1px}html body.mediawiki .mw-parser-output .ambox.mbox-small-left{margin:4px 1em 4px 0;overflow:hidden;width:238px;border-collapse:collapse;font-size:88%;line-height:1.25em}.mw-parser-output .ambox-speedy{border-left:10px solid #b32424;background-color:#fee7e6}.mw-parser-output .ambox-delete{border-left:10px solid #b32424}.mw-parser-output .ambox-content{border-left:10px solid #f28500}.mw-parser-output .ambox-style{border-left:10px solid #fc3}.mw-parser-output .ambox-move{border-left:10px solid #9932cc}.mw-parser-output .ambox-protection{border-left:10px solid #a2a9b1}.mw-parser-output .ambox .mbox-text{border:none;padding:0.25em 0.5em;width:100%}.mw-parser-output .ambox .mbox-image{border:none;padding:2px 0 2px 0.5em;text-align:center}.mw-parser-output .ambox .mbox-imageright{border:none;padding:2px 0.5em 2px 0;text-align:center}.mw-parser-output .ambox .mbox-empty-cell{border:none;padding:0;width:1px}.mw-parser-output .ambox .mbox-image-div{width:52px}@media(min-width:720px){.mw-parser-output .ambox{margin:0 10%}}@media print{body.ns-0 .mw-parser-output .ambox{display:none!important}}

/* end https://en.wikipedia.org/ */

</style>

<a href="Embedded_system" title="Embedded system">Embedded systems</a> 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 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.<a href="#cite_note-20">[20]</a>

<div class="mw-heading mw-heading2"><h2 id="(De)centralized_systems">(De)centralized systems</h2></div>

A <a href="True_random_number_generator" class="mw-redirect" title="True random number generator">true random number generator</a> (TRNG) can be a (de)central service. One example of a centralized system where a random number can be acquired is the randomness beacon service from the <a href="National_Institute_of_Standards_and_Technology" title="National Institute of Standards and Technology">National Institute of Standards and Technology</a>. The Cardano platform uses the participants of their decentralized <a href="Proof-of-stake" class="mw-redirect" title="Proof-of-stake">proof-of-stake</a> protocol to generate random numbers.<a href="#cite_note-trg-21">[21]</a>

<div class="mw-heading mw-heading2"><h2 id="Other_systems">Other systems</h2></div>

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.<a href="#cite_note-22">[22]</a>

<div class="mw-heading mw-heading2"><h2 id="Hardware-originated_entropy">Hardware-originated entropy</h2></div>

Modern <a href="CPU" class="mw-redirect" title="CPU">CPUs</a> and hardware often feature integrated generators that can provide high-quality and high-speed entropy to operating systems. On systems based on the <a href="Linux_kernel" title="Linux kernel">Linux kernel</a>, one can read the entropy generated from such a device through /dev/hw_random.<a href="#cite_note-23">[23]</a> However, sometimes /dev/hw_random may be slow;<a href="#cite_note-24">[24]</a><a href="#cite_note-25">[25]</a>

There are some companies manufacturing entropy generation devices, and some of them are shipped with drivers for Linux.<a href="#cite_note-26">[26]</a><a href="#cite_note-27">[27]</a>

On Linux system, one can install the rng-tools package<a href="#cite_note-28">[28]</a> that supports the <a href="True_random_number_generator" class="mw-redirect" title="True random number generator">true random number generators</a> (TRNGs) found in CPUs supporting the <a href="RDRAND" title="RDRAND">RDRAND</a> instruction, <a href="Trusted_Platform_Module" title="Trusted Platform Module">Trusted Platform Modules</a> and in some <a href="Intel" title="Intel">Intel</a>, <a href="AMD" title="AMD">AMD</a>, or <a href="VIA_Technologies" title="VIA Technologies">VIA</a> <a href="Chipset" title="Chipset">chipsets</a>,<a href="#cite_note-29">[29]</a> effectively increasing the entropy collected into /dev/random and potentially improving the cryptographic potential. This is especially useful on <a href="Headless_system" class="mw-redirect" title="Headless system">headless systems</a> that have no other sources of entropy.

<div class="mw-heading mw-heading2"><h2 id="Practical_implications">Practical implications</h2></div>

<a href="System_administrator" title="System administrator">System administrators</a>, especially those supervising Internet servers, have to ensure that the server processes will not halt because of entropy depletion. Entropy on <a href="Server_(computing)" title="Server (computing)">servers</a> 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 timings.

The entropy pool size in <a href="Linux" title="Linux">Linux</a> is viewable through the file /proc/sys/kernel/random/entropy_avail and should generally be at least 2000 bits (out of a maximum of 4096).<a href="#cite_note-30">[30]</a><a href="#cite_note-31">[31]</a> Entropy changes frequently.

Administrators responsible for systems that have low or zero entropy should not attempt to use <a href=".//dev/urandom" class="mw-redirect" title="/dev/urandom">/dev/urandom</a> as a substitute for /dev/random as this may cause SSL/TLS connections to have lower-grade encryption.<a href="#cite_note-32">[32]</a>

Some software systems change their <a href="Diffie-Hellman" class="mw-redirect" title="Diffie-Hellman">Diffie-Hellman</a> keys often, and this may in some cases help a server to continue functioning normally even with an entropy bottleneck.<a href="#cite_note-33">[33]</a>

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 <a href="Debian" title="Debian">Debian</a> that caused <a href="Exim4" class="mw-redirect" title="Exim4">exim4</a> to hang in some cases because of this.<a href="#cite_note-34">[34]</a>

<div class="mw-heading mw-heading3"><h3 id="Security">Security</h3></div>

Entropy sources can be used for keyboard timing attacks.<a href="#cite_note-35">[35]</a>

Entropy can affect the <a href="Cryptography" title="Cryptography">cryptography</a> (TLS/SSL) of a <a href="Server_(computing)" title="Server (computing)">server</a>: If a server fails to use a proper source of randomness, the keys generated by the server will be insecure.

In some cases a <a href="Hacker_(computer_security)" class="mw-redirect" title="Hacker (computer security)">cracker</a> (malicious attacker) can guess some <a href="Bit" title="Bit">bits</a> of entropy from the output of a <a href="Pseudorandom_number_generator" title="Pseudorandom number generator">pseudorandom number generator</a> (PRNG), and this happens when not enough entropy is introduced into the PRNG.<a href="#cite_note-36">[36]</a>

<div class="mw-heading mw-heading2"><h2 id="Potential_sources">Potential sources</h2></div>

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 <a href="Microphone" title="Microphone">microphone</a>, or by building a sensor to measure the <a href="Turbulence" title="Turbulence">air turbulence</a> inside a <a href="Disk_drive" class="mw-redirect" title="Disk drive">disk drive</a>.<a href="#cite_note-37">[37]</a>

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.<a href="#cite_note-38">[38]</a>

<a href="Cloudflare" title="Cloudflare">Cloudflare</a> use an image feed from a rack of 80 <a href="Lava_lamps" class="mw-redirect" title="Lava lamps">lava lamps</a> as an additional source of entropy.<a href="#cite_note-39">[39]</a>

<ul><li><a href="Entropy_(information_theory)" title="Entropy (information theory)">Entropy (information theory)</a></li>

<li><a href="Entropy" title="Entropy">Entropy</a></li>

<li><a href="Randomness" title="Randomness">Randomness</a></li></ul>

<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>

/* start https://en.wikipedia.org/ */

.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}

/* end https://en.wikipedia.org/ */

</style><div class="reflist reflist-columns references-column-width reflist-columns-2">

<li id="cite_note-1"><a href="#cite_ref-1">^</a> <a rel="nofollow" class="external text" href="http://linux.die.net/man/4/random">random(4) - Linux man page</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20071011084043/http://linux.die.net/man/4/random">Archived</a> 2007-10-11 at the <a href="Wayback_Machine" title="Wayback Machine">Wayback Machine</a> (die.net)

</li>

/* start https://en.wikipedia.org/ */

.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("./mw/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("./mw/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("./mw/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("./mw/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}

/* end https://en.wikipedia.org/ */

</style><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://ramcq.net/2005/09/25/missing-entropy/">"Robotic Tendencies » Missing entropy"</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20221206164925/https://ramcq.net/2005/09/25/missing-entropy/">Archived</a> from the original on 2022-12-06. Retrieved 2023-05-23.</cite>

</li>

<li id="cite_note-3"><a href="#cite_ref-3">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20210323204108/https://www.vanheusden.com/aed/">"audio entropy daemon"</a>. March 23, 2021. Archived from <a rel="nofollow" class="external text" href="https://www.vanheusden.com/aed/">the original</a> on 2021-03-23.</cite>

</li>

<li id="cite_note-4"><a href="#cite_ref-4">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://admin.fedoraproject.org/pkgdb/packages/name/audio-entropyd">"Fedora Package Database – audio-entropyd"</a>.</cite>

</li>

<li id="cite_note-5"><a href="#cite_ref-5">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20210323190233/https://www.vanheusden.com/ved/">"video_entropyd"</a>. March 23, 2021. Archived from <a rel="nofollow" class="external text" href="https://www.vanheusden.com/ved/">the original</a> on 2021-03-23.</cite>

</li>

<li id="cite_note-6"><a href="#cite_ref-6">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20200529190837/https://www.vanheusden.com/entropybroker/">"Entropy Broker"</a>. May 29, 2020. Archived from <a rel="nofollow" class="external text" href="https://www.vanheusden.com/entropybroker/">the original</a> on 2020-05-29.</cite>

</li>

<li id="cite_note-7"><a href="#cite_ref-7">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.issihosts.com/haveged/">"haveged – A simple entropy daemon"</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20121027075229/http://www.issihosts.com/haveged/">Archived</a> from the original on 27 October 2012. Retrieved 3 April 2011.</cite>

</li>

<li id="cite_note-8"><a href="#cite_ref-8">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20160402010703/https://linuxlink.timesys.com/docs/about_entropy">"Entropy and Random Devices | LinuxLink by TimeSys – Your Embedded Linux Resource"</a>. Archived from <a rel="nofollow" class="external text" href="https://linuxlink.timesys.com/docs/about_entropy">the original</a> on 2016-04-02. Retrieved 2007-10-15.</cite>

</li>

<li id="cite_note-9"><a href="#cite_ref-9">^</a> <a rel="nofollow" class="external text" href="http://ibofobi.dk/stuff/hurd-entropy/">/dev/{,u}random driver for GNU/Hurd</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20070918135155/http://ibofobi.dk/stuff/hurd-entropy/">Archived</a> 2007-09-18 at the <a href="Wayback_Machine" title="Wayback Machine">Wayback Machine</a> (ibofobi.dk)

</li>

<li id="cite_note-Solaris_devrandom-10">^ <a href="#cite_ref-Solaris_devrandom_10-0">a</a> <a href="#cite_ref-Solaris_devrandom_10-1">b</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.cosy.sbg.ac.at/%7Eandi/SUNrand/">"Solaris /dev/random through emulation"</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20071104145929/http://www.cosy.sbg.ac.at/~andi/SUNrand/">Archived</a> from the original on 2007-11-04. Retrieved 2007-10-15.</cite>

</li>

<li id="cite_note-11"><a href="#cite_ref-11">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20080511121018/http://docs.sun.com/app/docs/doc/816-5177/random-7d?a=view">"Solaris /dev/random"</a>. Archived from <a rel="nofollow" class="external text" href="http://docs.sun.com/app/docs/doc/816-5177/random-7d?a=view">the original</a> on 2008-05-11. Retrieved 2007-10-17.</cite>

</li>

<li id="cite_note-12"><a href="#cite_ref-12">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://r6.ca/RexxEGD/">"Rexx Entropy Gathering Daemon for OS/2"</a>. r6.ca. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20071031220059/http://r6.ca/RexxEGD/">Archived</a> from the original on 2007-10-31. Retrieved 2007-10-15.</cite>

</li>

<li id="cite_note-13"><a href="#cite_ref-13">^</a> <cite id="CITEREFMalayter2001" class="citation web cs1">Malayter, Ryan (November 9, 2001). <a rel="nofollow" class="external text" href="https://lists.gnupg.org/pipermail/gnupg-users/2001-November/010831.html">"GPL command-line shred alternative for Windows"</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20211027215112/https://lists.gnupg.org/pipermail/gnupg-users/2001-November/010831.html">Archived</a> from the original on October 27, 2021. Retrieved May 23, 2023.</cite>

</li>

<li id="cite_note-14"><a href="#cite_ref-14">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.mail-archive.com/openssl-dev@openssl.org/msg21829.html">"Source for entropy on Windows platforms with CryptoAPI installed"</a>. www.mail-archive.com. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20181002020158/https://www.mail-archive.com/openssl-dev@openssl.org/msg21829.html">Archived</a> from the original on 2018-10-02. Retrieved 2023-05-23.</cite>

</li>

<li id="cite_note-15"><a href="#cite_ref-15">^</a> <cite id="CITEREFMalayter2002" class="citation web cs1">Malayter, Ryan (February 15, 2002). <a rel="nofollow" class="external text" href="https://lists.gnupg.org/pipermail/gnupg-users/2002-February/011909.html">"How does Windows GnuPG generate random numbers on keygen?"</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20211201124427/https://lists.gnupg.org/pipermail/gnupg-users/2002-February/011909.html">Archived</a> from the original on December 1, 2021. Retrieved May 23, 2023.</cite>

</li>

<li id="cite_note-16"><a href="#cite_ref-16">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://archives.seul.org/or/cvs/Mar-2004/msg00078.html">"[or-cvs] Get entropy in windows"</a>. archives.seul.org. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20130507182643/http://archives.seul.org/or/cvs/Mar-2004/msg00078.html">Archived</a> from the original on 2013-05-07. Retrieved 2023-05-23.</cite>

</li>

<li id="cite_note-17"><a href="#cite_ref-17">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://msdn.microsoft.com/en-us/library/windows/desktop/aa375276(v=vs.85).aspx">"About CNG - Win32 apps"</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20180517152950/https://msdn.microsoft.com/en-us/library/windows/desktop/aa375276(v=vs.85).aspx">Archived</a> from the original on 2018-05-17. Retrieved 2018-05-17.</cite>

</li>

<li id="cite_note-18"><a href="#cite_ref-18">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://docs.microsoft.com/en-us/windows-hardware/drivers/bringup/uefi-entropy-gathering-protocol">"UEFI entropy gathering protocol - Windows drivers"</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20180517152846/https://docs.microsoft.com/en-us/windows-hardware/drivers/bringup/uefi-entropy-gathering-protocol">Archived</a> from the original on 2018-05-17. Retrieved 2018-05-17.</cite>

</li>

<li id="cite_note-19"><a href="#cite_ref-19">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://docs.microsoft.com/en-us/windows/win32/api/wincrypt/nf-wincrypt-cryptgenrandom">"CryptGenRandom function (Wincrypt.h) - Win32 apps"</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20200812010334/https://docs.microsoft.com/en-us/windows/win32/api/wincrypt/nf-wincrypt-cryptgenrandom">Archived</a> from the original on 2020-08-12. Retrieved 2020-08-31.</cite>

</li>

<li id="cite_note-20"><a href="#cite_ref-20">^</a> <cite id="CITEREFConstantin" class="citation news cs1">Constantin, Lucian. <a rel="nofollow" class="external text" href="https://www.networkworld.com/article/3009139/millions-of-embedded-devices-use-the-same-hard-coded-ssh-and-tls-private-keys.html">"Millions of embedded devices use the same hard-coded SSH and TLS private keys"</a>. Network World. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20181105202614/https://www.networkworld.com/article/3009139/millions-of-embedded-devices-use-the-same-hard-coded-ssh-and-tls-private-keys.html">Archived</a> from the original on 2018-11-05. Retrieved 2018-11-05.</cite>

</li>

<li id="cite_note-trg-21"><a href="#cite_ref-trg_21-0">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://iohk.io/en/blog/posts/2017/06/06/a-solution-for-scalable-randomness/">"A solution for scalable randomness"</a>. iohk.io. June 6, 2017. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20210417212225/https://iohk.io/en/blog/posts/2017/06/06/a-solution-for-scalable-randomness/">Archived</a> from the original on April 17, 2021. Retrieved September 14, 2020. </cite>

</li>

<li id="cite_note-22"><a href="#cite_ref-22">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://dwheeler.com/secure-programs/Secure-Programs-HOWTO/random-numbers.html">"Random Numbers"</a>. dwheeler.com. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20221230212607/https://dwheeler.com/secure-programs/Secure-Programs-HOWTO/random-numbers.html">Archived</a> from the original on 2022-12-30. Retrieved 2023-05-23.</cite>

</li>

<li id="cite_note-23"><a href="#cite_ref-23">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://marc.info/?l=kroupware&m=116377029100152&w=2">"'Re: SSL/TLS entropy problem,' - MARC"</a>. marc.info. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20181115224312/https://marc.info/?l=kroupware&m=116377029100152&w=2">Archived</a> from the original on 2018-11-15. Retrieved 2023-05-23.</cite>

</li>

<li id="cite_note-24"><a href="#cite_ref-24">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20071031091748/http://www.redhat.com/archives/rhl-devel-list/2004-August/msg00770.html">"Re: /dev/hw_random"</a>. Archived from <a rel="nofollow" class="external text" href="http://www.redhat.com/archives/rhl-devel-list/2004-August/msg00770.html">the original</a> on 2007-10-31. Retrieved 2007-10-15.</cite>

</li>

<li id="cite_note-25"><a href="#cite_ref-25">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20071112175917/http://www.redhat.com/archives/rhl-devel-list/2004-August/msg00786.html">"Re: /dev/hw_random"</a>. Archived from <a rel="nofollow" class="external text" href="http://www.redhat.com/archives/rhl-devel-list/2004-August/msg00786.html">the original</a> on 2007-11-12. Retrieved 2007-10-15.</cite>

</li>

<li id="cite_note-26"><a href="#cite_ref-26">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.std.com/~reinhold/truenoise.html">"Random Noise Sources"</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20071121080813/http://www.std.com/~reinhold/truenoise.html">Archived</a> from the original on 2007-11-21. Retrieved 2007-10-15.</cite>

</li>

<li id="cite_note-27"><a href="#cite_ref-27">^</a> <a rel="nofollow" class="external free" href="http://random.com.hr/products/random/hg324.html">http://random.com.hr/products/random/hg324.html</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20080513052740/http://random.com.hr/products/random/hg324.html">Archived</a> 2008-05-13 at the <a href="Wayback_Machine" title="Wayback Machine">Wayback Machine</a>

</li>

<li id="cite_note-28"><a href="#cite_ref-28">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://packages.debian.org/unstable/utils/rng-tools">"rng-tools"</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20071021031120/http://packages.debian.org/unstable/utils/rng-tools">Archived</a> from the original on 2007-10-21. Retrieved 2007-10-16.</cite>

</li>

<li id="cite_note-29"><a href="#cite_ref-29">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.kernel.org/doc/Documentation/hw_random.txt">"Linux support for random number generator in i8xx chipsets — The Linux Kernel documentation"</a>. www.kernel.org. 2000. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20130731115715/https://www.kernel.org/doc/Documentation/hw_random.txt">Archived</a> from the original on 31 July 2013.</cite>

</li>

<li id="cite_note-30"><a href="#cite_ref-30">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://lists.exim.org/lurker/message/20060217.000128.2064ef9b.en.html">"Re: [exim] no reply to STARTTLS"</a>. lists.exim.org. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20120722190957/https://lists.exim.org/lurker/message/20060217.000128.2064ef9b.en.html">Archived</a> from the original on 2012-07-22. Retrieved 2023-05-23.</cite>

</li>

<li id="cite_note-31"><a href="#cite_ref-31">^</a> <a rel="nofollow" class="external text" href="http://linux.die.net/man/4/random">random(4) Linux man page</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20071011084043/http://linux.die.net/man/4/random">Archived</a> 2007-10-11 at the <a href="Wayback_Machine" title="Wayback Machine">Wayback Machine</a>, die.net

</li>

<li id="cite_note-32"><a href="#cite_ref-32">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://marc.info/?l=kroupware&m=116375188915536&w=2">"'SSL/TLS entropy problem, aka pops timeouts (was: sasl ldap problem)' - MARC"</a>. marc.info. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20181115232141/https://marc.info/?l=kroupware&m=116375188915536&w=2">Archived</a> from the original on 2018-11-15. Retrieved 2023-05-23.</cite>

</li>

<li id="cite_note-33"><a href="#cite_ref-33">^</a> Josefsson, Simon; <a rel="nofollow" class="external text" href="http://www1.ietf.org/mail-archive/web/tls/current/msg01660.html">[TLS] Re: Short Ephermal Diffie-Hellman keys</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20071111095952/http://www1.ietf.org/mail-archive/web/tls/current/msg01660.html">Archived</a> 2007-11-11 at the <a href="Wayback_Machine" title="Wayback Machine">Wayback Machine</a> (ietf.org mailing list)

</li>

<li id="cite_note-34"><a href="#cite_ref-34">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20070117213440/http://lists.gnupg.org/pipermail/gnutls-dev/2004-December/000800.html">"[gnutls-dev] gnutls_rsa_params_init hangs. Is regenerating rsa-params once a day too frequent?"</a>. lists.gnupg.org. 14 December 2004. Archived from <a rel="nofollow" class="external text" href="http://lists.gnupg.org/pipermail/gnutls-dev/2004-December/000800.html">the original</a> on 2007-01-17.</cite>

</li>

<li id="cite_note-35"><a href="#cite_ref-35">^</a> Zalewski, Michal; <a rel="nofollow" class="external text" href="http://archive.cert.uni-stuttgart.de/bugtraq/2003/08/msg00213.html">Unix entropy source can be used for keystroke timing attacks</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20110719111151/http://archive.cert.uni-stuttgart.de/bugtraq/2003/08/msg00213.html">Archived</a> 2011-07-19 at the <a href="Wayback_Machine" title="Wayback Machine">Wayback Machine</a>, 2003

</li>

<li id="cite_note-36"><a href="#cite_ref-36">^</a> <a rel="nofollow" class="external text" href="http://osdir.com/ml/encryption.general/2005-01/msg00074.html">Re: entropy depletion (was: SSL/TLS passive sniffing)</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20110517025619/http://osdir.com/ml/encryption.general/2005-01/msg00074.html">Archived</a> 2011-05-17 at the <a href="Wayback_Machine" title="Wayback Machine">Wayback Machine</a>, 2005

</li>

<li id="cite_note-37"><a href="#cite_ref-37">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://archive.today/20120723103648/http://www.codeproject.com/internet/YourOwnSecureProtocol.asp?df=100&forumid=316484&exp=0&select=1846294">"Build your own cryptographically safe server/client protocol - 4.8.3. Collecting entropy"</a>. Archived from <a rel="nofollow" class="external text" href="http://www.codeproject.com/internet/YourOwnSecureProtocol.asp?df=100&forumid=316484&exp=0&select=1846294">the original</a> on 2012-07-23. Retrieved 2020-01-08.</cite>

</li>

<li id="cite_note-38"><a href="#cite_ref-38">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20100722164508/http://www.entropykey.co.uk/">"Simtec Electronics Entropy Key: USB True Random Number Generator"</a>. www.entropykey.co.uk. Archived from <a rel="nofollow" class="external text" href="http://www.entropykey.co.uk/">the original</a> on July 22, 2010.</cite>

</li>

<li id="cite_note-39"><a href="#cite_ref-39">^</a> <cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://blog.cloudflare.com/randomness-101-lavarand-in-production/">"Randomness 101: LavaRand in Production"</a>. The Cloudflare Blog. November 6, 2017. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20230501132603/https://blog.cloudflare.com/randomness-101-lavarand-in-production/">Archived</a> from the original on May 1, 2023. Retrieved May 23, 2023.</cite>

</li>

</ol></div>

<div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2></div>

<ul><li><a rel="nofollow" class="external text" href="https://archive.today/20130415082014/http://lfsbook.linuxfromscratch.org/hints/downloads/files/entropy.txt">Overview of entropy and of entropy generators in Linux</a></li></ul></div><div><div class="zim-footer">

This article is issued from <a class="external text" title="Last edited on 2025-03-12" href="https://en.wikipedia.org/wiki/?title=Entropy_(computing)&oldid=1280095933">Wikipedia</a>. The text is available under <a class="external text" href="https://creativecommons.org/licenses/by-sa/4.0/deed.en">Creative Commons Attribution-Share Alike 4.0</a> unless otherwise noted. Additional terms may apply for the media files.

</div>

</div></div>

</div>

</main>

</div>

</body></html>