(split) LDP v3.24 -> v3.29 の定型的な変更内容を反映。

[linuxjm/LDP_man-pages.git] / draft / man4 / random.4

.\" Copyright (c) 1997 John S. Kallal (kallal@voicenet.com)
.\"
.\" This is free documentation; you can redistribute it and/or
.\" modify it under the terms of the GNU General Public License as
.\" published by the Free Software Foundation; either version 2 of
.\" the License, or (at your option) any later version.
.\"
.\" Some changes by tytso and aeb.
.\"
.\" 2004-12-16, John V. Belmonte/mtk, Updated init and quit scripts
.\" 2004-04-08, AEB, Improved description of read from /dev/urandom
.\" 2008-06-20, George Spelvin <linux@horizon.com>,
.\"             Matt Mackall <mpm@selenic.com>
.\"     Add a Usage subsection that recommends most users to use
.\"     /dev/urandom, and emphasizes parsimonious usage of /dev/random.
.\"
.\" Japanese Version Copyright (c) 1998
.\"           ISHIKAWA Mutsumi, all rights reserved.
.\" Translated into Japanese Mon Jan 12 03:20:27 JST 1998
.\"         by ISHIKAWA Mutsumi <ishikawa@linux.or.jp>
.\" Japanese Version Last Modified Thu Feb  5 21:08:33 JST 1998
.\"     by ISHIKAWA Mutsumi <ishikawa@linux.or.jp>
.\" Updated & Modified Sun Jun  6 14:48:03 JST 2004
.\"     by Yuichi SATO <ysato444@yahoo.co.jp>
.\" Updated & Modified Tue Jan 18 04:21:16 JST 2005 by Yuichi SATO
.\" Updated & Modified Fri Apr 22 03:44:01 JST 2005 by Yuichi SATO
.\" Updated 2008-08-13, Akihiro MOTOKI <amotoki@dd.iij4u.or.jp>, LDP v3.05
.\"
.\"WORD:        random generator        Íð¿ô¥¸¥§¥Í¥ì¡¼¥¿
.\"
.TH RANDOM 4 2010-08-29 "Linux" "Linux Programmer's Manual"
.\"O .SH NAME
.SH ̾Á°
.\"O random, urandom \- kernel random number source devices
random, urandom \- ¥«¡¼¥Í¥ëÍð¿ô¥½¡¼¥¹¥Ç¥Ð¥¤¥¹
.\"O .SH DESCRIPTION
.SH ÀâÌÀ
.\"O The character special files \fI/dev/random\fP and
.\"O \fI/dev/urandom\fP (present since Linux 1.3.30)
.\"O provide an interface to the kernel's random number generator.
(Linux 1.3.30 ¤«¤éÄ󶡤µ¤ì¤Æ¤¤¤ë) \fI/dev/random\fP ¡¢
\fI/dev/urandom\fP ¥­¥ã¥é¥¯¥¿¥¹¥Ú¥·¥ã¥ë¥Õ¥¡¥¤¥ë¤Ï
¥«¡¼¥Í¥ëÍð¿ô¥¸¥§¥Í¥ì¡¼¥¿¤Ø¤Î¥¤¥ó¥¿¥Õ¥§¡¼¥¹¤òÄ󶡤¹¤ë¡£
.\"O File \fI/dev/random\fP has major device number 1
.\"O and minor device number 8.
.\"O File \fI/dev/urandom\fP has major device number 1 and minor device number 9.
\fI/dev/random\fP ¥Õ¥¡¥¤¥ë¤Ï¥á¥¸¥ã¡¼¥Ç¥Ð¥¤¥¹ÈÖ¹æ 1
¥Þ¥¤¥Ê¡¼¥Ç¥Ð¥¤¥¹ÈÖ¹æ 8 ¤Ç¤¢¤ë¡£
\fI/dev/urandom\fP ¤Ï¥á¥¸¥ã¡¼¥Ç¥Ð¥¤¥¹ÈÖ¹æ 1
¥Þ¥¤¥Ê¡¼¥Ç¥Ð¥¤¥¹ÈÖ¹æ 9 ¤Ç¤¢¤ë¡£
.LP
.\"O The random number generator gathers environmental noise
.\"O from device drivers and other sources into an entropy pool.
Íð¿ô¥¸¥§¥Í¥ì¡¼¥¿¤Ï¥Ç¥Ð¥¤¥¹¥É¥é¥¤¥Ð¤ä¤½¤Î¾¤Î¸»¤«¤é¤Î´Ä¶­¥Î¥¤¥º¤ò
¥¨¥ó¥È¥í¥Ô¡¼¡¦¥×¡¼¥ë¤Ø½¸¤á¤ë¡£
.\"O The generator also keeps an estimate of the
.\"O number of bits of noise in the entropy pool.
¤Þ¤¿¡¢¥¸¥§¥Í¥ì¡¼¥¿¤Ï¥¨¥ó¥È¥í¥Ô¡¼¡¦¥×¡¼¥ëÆâ¤Î¥Î¥¤¥º¤Î¥Ó¥Ã¥È¿ô¤Î¿äÄêÃͤò
ÊÝ»ý¤¹¤ë¡£
.\"O From this entropy pool random numbers are created.
¤³¤Î¥¨¥ó¥È¥í¥Ô¡¼¡¦¥×¡¼¥ë¤«¤éÍð¿ô¤¬À¸À®¤µ¤ì¤ë¡£
.LP
.\"O When read, the \fI/dev/random\fP device will only return random bytes
.\"O within the estimated number of bits of noise in the entropy
.\"O pool.
.\"O \fI/dev/random\fP should be suitable for uses that need very
.\"O high quality randomness such as one-time pad or key generation.
Æɤ߹þ¤ß¤¬¹Ô¤ï¤ì¤ë¤È¡¢
\fI/dev/random\fP
¥Ç¥Ð¥¤¥¹¤Ï¥¨¥ó¥È¥í¥Ô¡¼¡¦¥×¡¼¥ë¤Î¥Î¥¤¥º¥Ó¥Ã¥È¤Î¿ô¤Î¿äÄêÃͤΤ¦¤Á¡¢
¥é¥ó¥À¥à¥Ð¥¤¥È¤Î¤ß¤òÊÖ¤¹¡£
\fI/dev/random\fP ¤Ï¥ï¥ó¥¿¥¤¥à¥Ñ¥Ã¥É (one-time pad) ¤ä¸°¤ÎÀ¸À®¤Î¤è¤¦¤Ê
Èó¾ï¤Ë¹â¤¤ÉʼÁ¤ò»ý¤Ã¤¿Ìµºî°ÙÀ­¤¬É¬ÍפˤʤëÍÑÅӤ˸þ¤¤¤Æ¤¤¤ë¤À¤í¤¦¡£
.\"O When the entropy pool is empty, reads from \fI/dev/random\fP will block
.\"O until additional environmental noise is gathered.
¥¨¥ó¥È¥í¥Ô¡¼¡¦¥×¡¼¥ë¤¬¶õ¤Î»þ¤Ï¡¢\fI/dev/random\fP ¤«¤é¤ÎÆɤ߽Ф·¤Ï¡¢
¹¹¤Ê¤ë´Ä¶­¥Î¥¤¥º¤¬ÆÀ¤é¤ì¤ë¤Þ¤Ç¡¢¥Ö¥í¥Ã¥¯¤µ¤ì¤ë¡£
.LP
.\"O A read from the \fI/dev/urandom\fP device will not block
.\"O waiting for more entropy.
.\"O As a result, if there is not sufficient entropy in the
.\"O entropy pool, the returned values are theoretically vulnerable to a
.\"O cryptographic attack on the algorithms used by the driver.
.\"O Knowledge of how to do this is not available in the current unclassified
.\"O literature, but it is theoretically possible that such an attack may
.\"O exist.
.\"O If this is a concern in your application, use \fI/dev/random\fP
.\"O instead.
\fI/dev/urandom\fP ¥Ç¥Ð¥¤¥¹¤«¤éÆɤ߽Ф·¤Ç¤Ï¡¢
¥¨¥ó¥È¥í¥Ô¡¼¤¬¤è¤ê¹â¤¯¤Ê¤ë¤Î¤òÂԤĤ¿¤á¤Î¥Ö¥í¥Ã¥¯¤Ï¹Ô¤ï¤ì¤Ê¤¤¡£
¤½¤Î·ë²Ì¡¢¤â¤·¥¨¥ó¥È¥í¥Ô¡¼¡¦¥×¡¼¥ë¤Ë½½Ê¬¤Ê¥¨¥ó¥È¥í¥Ô¡¼¤¬Â¸ºß¤·¤Ê¤¤¾ì¹ç¡¢
ÊÖ¤êÃͤϤ³¤Î¥É¥é¥¤¥Ð¤Ç»È¤ï¤ì¤Æ¤¤¤ë¥¢¥ë¥´¥ê¥º¥à¤Ë´ð¤Å¤¯°Å¹æ¹¶·â¤ËÂФ·¤Æ¡¢
ÏÀÍýŪ¤Ë¤Ï¼å¤¯¤Ê¤ë¤³¤È¤Ë¤Ê¤ë¡£
¤³¤Î¹¶·â¤ò¤É¤Î¤è¤¦¤Ë¹Ô¤¦¤«¤È¤¤¤¦»ö¤Ë¤Ä¤¤¤Æ¤Ï¡¢¸½ºß¸¦µæÏÀʸ¤Ê¤É¤Î
·Á¤ÇÆþ¼ê¤Ç¤­¤ë»ñÎÁ¤Ï¤Ê¤¤¡¢¤·¤«¤·¡¢¤½¤Î¤è¤¦¤Ê¹¶·â¤ÏÏÀÍýŪ¤Ë¸ºß²Äǽ¤Ç¤¢¤ë¡£
¤â¤·¡¢¤³¤Î»ö¤¬¿´Çۤʤ顢(\fI/dev/urandom\fP ¤Ç¤Ï¤Ê¤¯)
\fI/dev/random\fP ¤òÍøÍѤ¹¤ì¤Ð¤¤¤¤¡£
.\"O .SS Usage
.SS »È¤¤Êý
.\"O If you are unsure about whether you should use
.\"O .IR /dev/random
.\"O or
.\"O .IR /dev/urandom ,
.\"O then probably you want to use the latter.
.\"O As a general rule,
.\"O .IR /dev/urandom
.\"O should be used for everything except long-lived GPG/SSL/SSH keys.
.I /dev/random
¤È
.I /dev/urandom
¤Î¤É¤Á¤é¤ò»È¤¦¤Ù¤­¤«Ì¤ä¿¾ì¹ç¡¢¤¿¤¤¤Æ¤¤¤Ï
.I /dev/urandom
¤ÎÊý¤ò»È¤¤¤¿¤¤¤È»×¤Ã¤Æ¤¤¤ë¤Ï¤º¤À¤í¤¦¡£
°ìÈ̤ˡ¢Ä¹´ü¤ËÅϤäƻȤï¤ì¤ë GPG/SSL/SSH ¤Î¥­¡¼°Ê³°¤ÎÁ´¤Æ¤Î¤â¤Î¤Ë
.I /dev/urandom
¤ò»ÈÍѤ¹¤Ù¤­¤Ç¤¢¤ë¡£

.\"O If a seed file is saved across reboots as recommended below (all major
.\"O Linux distributions have done this since 2000 at least), the output is
.\"O cryptographically secure against attackers without local root access as
.\"O soon as it is reloaded in the boot sequence, and perfectly adequate for
.\"O network encryption session keys.
.\"O Since reads from
.\"O .I /dev/random
.\"O may block, users will usually want to open it in nonblocking mode
.\"O (or perform a read with timeout),
.\"O and provide some sort of user notification if the desired
.\"O entropy is not immediately available.
²¼µ­¤Ç¿ä¾©¤·¤Æ¤¤¤ë¤è¤¦¤ËºÆµ¯Æ°¤ÎÁ°¸å¤ÇÍð¿ô¼ï¥Õ¥¡¥¤¥ë¤¬Êݸ¤µ¤ì¤ë¾ì¹ç
(Á´¤Æ¤Î¼ç¤Ê Linux ¤Î¥Ç¥£¥¹¥È¥ê¥Ó¥å¡¼¥·¥ç¥ó¤Ï¾¯¤Ê¤¯¤È¤â 2000 ǯ°Ê¹ß¤Ï
Íð¿ô¼ï¤òÊݸ¤¹¤ë¤è¤¦¤Ë¤Ê¤Ã¤Æ¤¤¤ë)¡¢µ¯Æ°¥·¡¼¥±¥ó¥¹¤Ë¤ª¤¤¤ÆÍð¿ô¼ï¤¬
ºÆ¥í¡¼¥É¤µ¤ì¤¿Ä¾¸å¤«¤é¡¢¤½¤Î½ÐÎÏ¤Ï¥í¡¼¥«¥ë¤Î¥ë¡¼¥È¥¢¥¯¥»¥¹¤¬¤Ç¤­¤Ê¤¤
¹¶·â¼Ô¤ËÂФ·¤Æ°Å¹æŪ¤Ë°ÂÁ´¤Ê¤â¤Î¤È¤Ê¤ê¡¢¥Í¥Ã¥È¥ï¡¼¥¯°Å¹æ²½¤Î¥»¥Ã¥·¥ç¥ó¥­¡¼
¤È¤·¤Æ»È¤¦¤Ë¤Ï´°Á´¤ËºÇŬ¤Ê¤â¤Î¤È¤Ê¤ë¡£
.I /dev/random
¤«¤é¤ÎÆɤ߽Ф·¤ÏÄä»ß (block) ¤¹¤ë²ÄǽÀ­¤¬¤¢¤ë¤Î¤Ç¡¢¥æ¡¼¥¶¤ÏÉáÄÌ
¤³¤Î¥Õ¥¡¥¤¥ë¤òÈóÄä»ß (nonblocking) ¥â¡¼¥É¤Ç³«¤³¤¦¤È¤·
(¤â¤·¤¯¤Ï¥¿¥¤¥à¥¢¥¦¥È¤ò»ØÄꤷ¤ÆÆɤ߽Ф·¤ò¼Â¹Ô¤·)¡¢´õ˾¤¹¤ë¥ì¥Ù¥ë¤Î
¥¨¥ó¥È¥í¥Ô¡¼¤Ï¤¹¤°¤Ë¤ÏÍøÍѤǤ­¤Ê¤¤¾ì¹ç¤Ë¤Ï¡¢²¿¤é¤«¤ÎÄÌÃΤò¹Ô¤¦¤³¤È¤À¤í¤¦¡£

.\"O The kernel random-number generator is designed to produce a small
.\"O amount of high-quality seed material to seed a
.\"O cryptographic pseudo-random number generator (CPRNG).
.\"O It is designed for security, not speed, and is poorly
.\"O suited to generating large amounts of random data.
.\"O Users should be very economical in the amount of seed
.\"O material that they read from
.\"O .IR /dev/urandom
.\"O (and
.\"O .IR /dev/random );
.\"O unnecessarily reading large quantities of data from this device will have
.\"O a negative impact on other users of the device.
¥«¡¼¥Í¥ë¤ÎÍð¿ô¥¸¥§¥Í¥ì¡¼¥¿¤Ï¡¢°Å¹æµ¿»÷Íð¿ô¥¸¥§¥Í¥ì¡¼¥¿ (Cryptographic
pseudo-random number generator; CPRNG) ¤Î¼ï¤È¤·¤Æ»ÈÍѤǤ­¤ë
¹âÉʼÁ¤ÊÍð¿ô¼ï¤ÎºàÎÁ¤ò¾¯¤·À¸À®¤¹¤ë¤¿¤á¤ËÀ߷פµ¤ì¤Æ¤¤¤ë¡£
¤³¤ì¤Ï®Å٤ǤϤʤ¯°ÂÁ´À­¤ò½Å»ë¤·¤ÆÀ߷פµ¤ì¤Æ¤ª¤ê¡¢
¥é¥ó¥À¥à¤Ê¥Ç¡¼¥¿¤òÂçÎ̤ËÀ¸À®¤¹¤ë¤Î¤Ë¤ÏÁ´¤¯¤â¤Ã¤ÆŬ¤·¤Æ¤¤¤Ê¤¤¡£
¥æ¡¼¥¶¤Ï
.I /dev/urandom
(¤È
.IR /dev/random )
¤«¤éÆɤ߽Ф¹Íð¿ô¼ï¤ÎºàÎÁ¤ÎÎ̤ò¤Ç¤­¤ë¤À¤±ÀáÌ󤹤٤­¤Ç¤¢¤ë¡£
¤³¤Î¥Ç¥Ð¥¤¥¹¤«¤éÉÔɬÍפËÂçÎ̤Υǡ¼¥¿¤òÆɤ߽Ф¹¤È¡¢¤³¤Î¥Ç¥Ð¥¤¥¹¤ò»È¤¦
¾¤Î¥æ¡¼¥¶¤Ë¥Þ¥¤¥Ê¥¹¤Î±Æ¶Á¤òÍ¿¤¨¤Æ¤·¤Þ¤¦¤À¤í¤¦¡£

.\"O The amount of seed material required to generate a cryptographic key
.\"O equals the effective key size of the key.
.\"O For example, a 3072-bit RSA
.\"O or Diffie-Hellman private key has an effective key size of 128 bits
.\"O (it requires about 2^128 operations to break) so a key generator only
.\"O needs 128 bits (16 bytes) of seed material from
.\"O .IR /dev/random .
°Å¹æ¸°¤òÀ¸À®¤¹¤ë¤Î¤ËɬÍפÊÍð¿ô¼ï¤ÎºàÎÁ¤ÎÎ̤ϡ¢¸°¤Î¼Â¸ú¥µ¥¤¥º¤ÈƱ¤¸¤Ç¤¢¤ë¡£
Î㤨¤Ð¡¢3072 ¥Ó¥Ã¥È¤Î RSA ¤ª¤è¤Ó Diffie-Hellman ¤ÎÈëÌ©¸°¤Î¼Â¸ú¥µ¥¤¥º¤Ï
128 ¥Ó¥Ã¥È (¤³¤ÎÈëÌ©¸°¤òÇˤë¤Ë¤Ï 2^128 ²ó¤ÎÁàºî¤¬É¬ÍפȤ¤¤¦¤³¤È) ¤Ç¤¢¤ê¡¢
¤½¤Î¤¿¤á¸°À¸À®´ï¤¬
.I /dev/random
¤«¤éÆɤ߽Ф¹É¬Íפ¬¤¢¤ëÍð¿ô¼ï¤ÎºàÎÁ¤ÎÎÌ¤Ï 128 ¥Ó¥Ã¥È (16 ¥Ð¥¤¥È) ¤À¤±¤Ç¤¢¤ë¡£

.\"O While some safety margin above that minimum is reasonable, as a guard
.\"O against flaws in the CPRNG algorithm, no cryptographic primitive
.\"O available today can hope to promise more than 256 bits of security,
.\"O so if any program reads more than 256 bits (32 bytes) from the kernel
.\"O random pool per invocation, or per reasonable reseed interval (not less
.\"O than one minute), that should be taken as a sign that its cryptography is
.\"O .I not
.\"O skilfully implemented.
CPRNG ¥¢¥ë¥´¥ê¥º¥à¤Î·ç´Ù¤ËÂФ¹¤ëÊݸî¤È¤·¤Æ¡¢¤³¤ÎºÇ¾®ÃͤËÂФ·¤Æ¤¤¤¯¤é¤«¤Î
°ÂÁ´¾å¤Î¥Þ¡¼¥¸¥ó¤ò¼è¤ë¤Î¤Ï¤â¤Ã¤È¤â¤À¤¬¡¢¸½ºßÍøÍѲÄǽ¤Ê°Å¹æ¥×¥ê¥ß¥Æ¥£¥Ö¤Ç
256 ¥Ó¥Ã¥È¤è¤ê¿¤¯¤Î°ÂÁ´¤ÊÍð¿ô¤òɬÍפȤ¹¤ë¤è¤¦¤Ê¤â¤Î¤Ï¤Ê¤¤¡£
µ¯Æ°¤¹¤ëÅ٤ˡ¢¤â¤·¤¯¤ÏÍð¿ô¼ï¤òÊѹ¹¤¹¤ëÂÅÅö¤Ê´Ö³Ö (1 ʬ¤è¤êû¤¯¤Ê¤ë¤³¤È¤Ï¤Ê¤¤)
¤ÎÅ٤ˡ¢¥«¡¼¥Í¥ë¤ÎÍð¿ô¥×¡¼¥ë¤«¤é 256 ¥Ó¥Ã¥È (32 ¥Ð¥¤¥È) ¤è¤ê¤¿¤¯¤µ¤óÆɤ߽Ф¹
¤è¤¦¤Ê¾ì¹ç¤Ë¤Ï¡¢¤½¤Î¥×¥í¥°¥é¥à¤Î°Å¹æ½èÍý¤¬¤¦¤Þ¤¯¼ÂÁõ¤µ¤ì¤Æ¡Ö¤¤¤Ê¤¤¡×²ÄǽÀ­¤¬
¤¢¤ë¤È¹Í¤¨¤ë¤Ù¤­¤Ç¤¢¤í¤¦¡£
.\"O .SS Configuration
.SS ÀßÄê
.\"O If your system does not have
.\"O \fI/dev/random\fP and \fI/dev/urandom\fP created already, they
.\"O can be created with the following commands:
¥·¥¹¥Æ¥à¤Ë¤¢¤é¤«¤¸¤áºîÀ®¤µ¤ì¤¿ \fI/dev/random\fP ¤È
\fI/dev/urandom\fP ¤¬Â¸ºß¤·¤Ê¤¤¤Ê¤é¡¢¼¡¤Î¤è¤¦¤Ê¥³¥Þ¥ó¥É¤ÇºîÀ®¤Ç¤­¤ë¡£
.nf

    mknod \-m 644 /dev/random c 1 8
    mknod \-m 644 /dev/urandom c 1 9
    chown root:root /dev/random /dev/urandom
.fi

.\"O When a Linux system starts up without much operator interaction,
.\"O the entropy pool may be in a fairly predictable state.
¥ª¥Ú¥ì¡¼¥¿¤ÎÁàºî¤Ê¤·¤Ë Linux ¥·¥¹¥Æ¥à¤¬µ¯Æ°¤·¤¿Ä¾¸å¤Ï¡¢
¥¨¥ó¥È¥í¥Ô¡¼¡¦¥×¡¼¥ë¤Ï°Õ³°À­¤Î˳¤·¤¤¶Ñ°ì¤Ê¾õÂ֤ˤ¢¤ë¤À¤í¤¦¡£
.\"O This reduces the actual amount of noise in the entropy pool
.\"O below the estimate.
.\"O In order to counteract this effect, it helps to carry
.\"O entropy pool information across shut-downs and start-ups.
¤³¤ì¤Ë¤è¤ê¡¢¥¨¥ó¥È¥í¥Ô¡¼¡¦¥×¡¼¥ë¤Î¼ÂºÝ¤Î¥Î¥¤¥ºÎ̤Ïɾ²ÁÃͤè¤ê¾¯¤Ê¤¯¤Ê¤ë¡£
¤³¤Î¸ú²Ì¤òÂǤÁ¾Ã¤¹¤¿¤á¤Ë¡¢¥·¥ã¥Ã¥È¥À¥¦¥ó¤«¤é (¼¡¤Î) µ¯Æ°»þ¤Þ¤Ç»ý¤Á±Û¤·¤¿
¥¨¥ó¥È¥í¥Ô¡¼¡¦¥×¡¼¥ë¤Î¾ðÊ󤬽õ¤±¤Ë¤Ê¤ë¡£
.\"O To do this, add the following lines to an appropriate script
.\"O which is run during the Linux system start-up sequence:
¥¨¥ó¥È¥í¥Ô¡¼¡¦¥×¡¼¥ë¤ò»ý¤Á±Û¤¹¤¿¤á¤Ë¤Ï¡¢
Linux ¥·¥¹¥Æ¥à¤Îµ¯Æ°»þ¤Ë¼Â¹Ô¤µ¤ì¤ëŬÀڤʥ¹¥¯¥ê¥×¥È¤Ë¡¢
°Ê²¼¤Î¹Ô¤òÄɲ乤ì¤Ð¤è¤¤:
.nf

    echo "Initializing random number generator..."
    random_seed=/var/run/random-seed
.\"O     # Carry a random seed from start-up to start-up
.\"O     # Load and then save the whole entropy pool
    # Íð¿ô¼ï¤òº£²ó¤Î¥¹¥¿¡¼¥È¥¢¥Ã¥×¤«¤é¼¡²ó¤Î¥¹¥¿¡¼¥È¥¢¥Ã¥×¤Þ¤Ç»ý¤Á±Û¤¹¡£
    # ¥í¡¼¥É¤ò¹Ô¤¤¡¢¤½¤Î¸å¡¢Á´¤Æ¤Î¥¨¥ó¥È¥í¥Ô¡¼¡¦¥×¡¼¥ë¤òÊݸ¤¹¤ë¡£
    if [ \-f $random_seed ]; then
        cat $random_seed >/dev/urandom
    else
        touch $random_seed
    fi
    chmod 600 $random_seed
    poolfile=/proc/sys/kernel/random/poolsize
    [ \-r $poolfile ] && bytes=\`cat $poolfile\` || bytes=512
    dd if=/dev/urandom of=$random_seed count=1 bs=$bytes
.fi

.\"O Also, add the following lines in an appropriate script which is
.\"O run during the Linux system shutdown:
¤Þ¤¿¡¢Linux ¥·¥¹¥Æ¥à¤Î¥·¥ã¥Ã¥È¥À¥¦¥ó»þ¤Ë¼Â¹Ô¤µ¤ì¤ëŬÀڤʥ¹¥¯¥ê¥×¥È¤Ë¡¢
°Ê²¼¤Î¹Ô¤òÄɲ乤ì¤Ð¤è¤¤:
.nf

.\"O     # Carry a random seed from shut-down to start-up
.\"O     # Save the whole entropy pool
    # Íð¿ô¼ï¤òº£²ó¤Î¥·¥ã¥Ã¥È¥À¥¦¥ó¤«¤é¼¡²ó¤Î¥¹¥¿¡¼¥È¥¢¥Ã¥×¤Þ¤Ç»ý¤Á±Û¤¹¡£
    # Á´¤Æ¤Î¥¨¥ó¥È¥í¥Ô¡¼¡¦¥×¡¼¥ë¤òÊݸ¤¹¤ë¡£
    echo "Saving random seed..."
    random_seed=/var/run/random-seed
    touch $random_seed
    chmod 600 $random_seed
    poolfile=/proc/sys/kernel/random/poolsize
    [ \-r $poolfile ] && bytes=\`cat $poolfile\` || bytes=512
    dd if=/dev/urandom of=$random_seed count=1 bs=$bytes
.fi
.\"O .SS "/proc Interface"
.SS "/proc ¥¤¥ó¥¿¥Õ¥§¡¼¥¹"
.\"O The files in the directory
.\"O .I /proc/sys/kernel/random
.\"O (present since 2.3.16) provide an additional interface to the
.\"O .I /dev/random
.\"O device.
¥Ç¥£¥ì¥¯¥È¥ê
.I /proc/sys/kernel/random
¤Ë¤¢¤ë¥Õ¥¡¥¤¥ë (2.3.16 ¤«¤é¸ºß¤¹¤ë) ¤Ï¡¢
.I /dev/random
¥Ç¥Ð¥¤¥¹¤Ø¤Î¤½¤Î¾¤Î¥¤¥ó¥¿¥Õ¥§¡¼¥¹¤òÄ󶡤¹¤ë¡£
.LP
.\"O The read-only file
.\"O .I entropy_avail
.\"O gives the available entropy.
.\"O Normally, this will be 4096 (bits),
.\"O a full entropy pool.
Æɤ߹þ¤ßÀìÍѤΥե¡¥¤¥ë
.I entropy_avail
¤Ï»ÈÍѲÄǽ¤Ê¥¨¥ó¥È¥í¥Ô¡¼¤òɽ¤¹¡£
Ä̾¤³¤ì¤Ï 4096 (¥Ó¥Ã¥È) ¤Ë¤Ê¤ê¡¢¥¨¥ó¥È¥í¥Ô¡¼¡¦¥×¡¼¥ë¤¬ËþÇդξõÂ֤Ǥ¢¤ë¡£
.LP
.\"O The file
.\"O .I poolsize
.\"O gives the size of the entropy pool.
¥Õ¥¡¥¤¥ë
.I poolsize
¤Ï¥¨¥ó¥È¥í¥Ô¡¼¡¦¥×¡¼¥ë¤Î¥µ¥¤¥º¤òɽ¤¹¡£
.\"O The semantics of this file vary across kernel versions:
¤³¤Î¥Õ¥¡¥¤¥ë¤Î°ÕÌ£¤Ï¥«¡¼¥Í¥ë¥Ð¡¼¥¸¥ç¥ó¤Ë¤è¤ê°Û¤Ê¤ë¡£
.RS
.TP 12
Linux 2.4:
.\"O This file gives the size of the entropy pool in
.\"O .IR bytes .
.\"O Normally, this file will have the value 512, but it is writable,
.\"O and can be changed to any value for which an algorithm is available.
.\"O The choices are 32, 64, 128, 256, 512, 1024, or 2048.
¤³¤Î¥Õ¥¡¥¤¥ë¤Ï¥¨¥ó¥È¥í¥Ô¡¼¡¦¥×¡¼¥ë¤Î¥µ¥¤¥º¤ò¡Ö¥Ð¥¤¥È¡×ñ°Ì¤Çµ¬Äꤹ¤ë¡£
Ä̾¤³¤Î¥Õ¥¡¥¤¥ë¤ÎÃÍ¤Ï 512 ¤Ë¤Ê¤ë¤¬¡¢½ñ¤­¹þ¤ß²Äǽ¤Ç¤¢¤ê¡¢
¥¢¥ë¥´¥ê¥º¥à¤ÇÍøÍѲÄǽ¤ÊǤ°Õ¤ÎÃͤËÊѹ¹¤Ç¤­¤ë¡£
ÁªÂò²Äǽ¤ÊÃÍ¤Ï 32, 64, 128, 256, 512, 1024, 2048 ¤Ç¤¢¤ë¡£
.TP
Linux 2.6:
.\"O This file is read-only, and gives the size of the entropy pool in
.\"O .IR bits .
.\"O It contains the value 4096.
¤³¤Î¥Õ¥¡¥¤¥ë¤ÏÆɤ߽Ф·ÀìÍѤǤ¢¤ê¡¢
¥¨¥ó¥È¥í¥Ô¡¼¡¦¥×¡¼¥ë¤Î¥µ¥¤¥º¤ò¡Ö¥Ó¥Ã¥È¡×ñ°Ì¤Çµ¬Äꤹ¤ë¡£
ÃÍ¤Ï 4096 ¤Ç¤¢¤ë¡£
.RE
.LP
.\"O The file
.\"O .I read_wakeup_threshold
.\"O contains the number of bits of entropy required for waking up processes
.\"O that sleep waiting for entropy from
.\"O .IR /dev/random .
¥Õ¥¡¥¤¥ë
.I read_wakeup_threshold
¤Ï
.I /dev/random
¤«¤é¤Î¥¨¥ó¥È¥í¥Ô¡¼¤òÂԤäƵٻߤ·¤Æ¤¤¤ë¥×¥í¥»¥¹¤òµ¯¤³¤¹¤Î¤ËɬÍפÊ
¥¨¥ó¥È¥í¥Ô¡¼¤Î¥Ó¥Ã¥È¿ô¤òÊÝ»ý¤·¤Æ¤¤¤ë¡£
.\"O The default is 64.
¥Ç¥Õ¥©¥ë¥È¤Ï 64 ¤Ç¤¢¤ë¡£
.\"O The file
.\"O .I write_wakeup_threshold
.\"O contains the number of bits of entropy below which we wake up
.\"O processes that do a
.\"O .BR select (2)
.\"O or
.\"O .BR poll (2)
.\"O for write access to
.\"O .IR /dev/random .
¥Õ¥¡¥¤¥ë
.I write_wakeup_threshold
¤Ï¥¨¥ó¥È¥í¥Ô¡¼¤Î¥Ó¥Ã¥È¿ô¤òÊÝ»ý¤·¤Æ¤ª¤ê¡¢¤³¤ÎÃͰʲ¼¤Ë¤Ê¤Ã¤¿¤é
.I /dev/random
¤Ø¤Î½ñ¤­¹þ¤ß¥¢¥¯¥»¥¹¤Î¤¿¤á¤Ë
.BR select (2)
¤Þ¤¿¤Ï
.BR poll (2)
¤ò¼Â¹Ô¤¹¤ë¥×¥í¥»¥¹¤òµ¯¤³¤¹¡£
.\"O These values can be changed by writing to the files.
¤³¤ÎÃͤϥե¡¥¤¥ë¤Ë½ñ¤­¹þ¤ß¤ò¹Ô¤¦¤³¤È¤Ë¤è¤Ã¤ÆÊѹ¹¤Ç¤­¤ë¡£
.LP
.\"O The read-only files
.\"O .I uuid
.\"O and
.\"O .I boot_id
.\"O contain random strings like 6fd5a44b-35f4-4ad4-a9b9-6b9be13e1fe9.
Æɤ߹þ¤ßÀìÍѤΥե¡¥¤¥ë
.I uuid
¤È
.I boot_id
¤Ï 6fd5a44b-35f4-4ad4-a9b9-6b9be13e1fe9 ¤Î¤è¤¦¤Ê
¥é¥ó¥À¥à¤Êʸ»úÎó¤òÊÝ»ý¤·¤Æ¤¤¤ë¡£
.\"O The former is generated afresh for each read, the latter was
.\"O generated once.
Á°¼Ô¤ÏÆɤ߹þ¤ß¤ÎÅ٤˿·¤¿¤ËÀ¸À®¤µ¤ì¡¢
¸å¼Ô¤Ï 1 ÅÙ¤À¤±À¸À®¤µ¤ì¤ë¡£
.\"O .SH FILES
.SH ¥Õ¥¡¥¤¥ë
/dev/random
.br
/dev/urandom
.\"O .\" .SH AUTHOR
.\" .SH Ãø¼Ô
.\"O .\" The kernel's random number generator was written by
.\"O .\" Theodore Ts'o (tytso@athena.mit.edu).
.\" ¥«¡¼¥Í¥ë¡¦¥é¥ó¥À¥à¥Ê¥ó¥Ð¡¼¡¦¥¸¥§¥Í¥ì¡¼¥¿¤Ï Theodora Ts'o
.\" (tytso@athena.mit.edu) ¤Ë¤è¤Ã¤Æ½ñ¤«¤ì¤¿¡£
.\"O .SH "SEE ALSO"
.SH ´ØÏ¢¹àÌÜ
mknod (1)
.br
RFC\ 1750, "Randomness Recommendations for Security"
.\" .SH ËÝÌõ¼Ô
.\" ÀÐÀî ËÓ <ishikawa@linux.or.jp>