277 lines
7.2 KiB
Groff
277 lines
7.2 KiB
Groff
.rn '' }`
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'''
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'''
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.de Sh
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.br
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\fB\\$1\fR
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..
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.de Sp
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'''
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'''
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''' Set up \*(-- to give an unbreakable dash;
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''' string Tr holds user defined translation string.
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''' Bell System Logo is used as a dummy character.
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'''
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.tr \(*W-|\(bv\*(Tr
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.ie n \{\
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.ds -- \(*W-
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.ds PI pi
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.if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch
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.if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch
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.ds L" ""
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''' \*(M", \*(S", \*(N" and \*(T" are the equivalent of
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''' \*(L" and \*(R", except that they are used on ".xx" lines,
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''' such as .IP and .SH, which do another additional levels of
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''' double-quote interpretation
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'br\}
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.\" If the F register is turned on, we'll generate
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.\" index entries out stderr for the following things:
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.\" TH Title
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.\" SH Header
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.\" Sh Subsection
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.\" Ip Item
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.\" X<> Xref (embedded
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.\" Of course, you have to process the output yourself
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.\" in some meaninful fashion.
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.if \nF \{
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.de IX
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.tm Index:\\$1\t\\n%\t"\\$2"
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..
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.nr % 0
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.rr F
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.\}
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.TH RAND_add 3 "0.9.5a" "22/Jul/2000" "OpenSSL"
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.UC
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.if n .hy 0
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.if n .na
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.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p'
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.de CQ \" put $1 in typewriter font
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.ft CW
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'if n "\c
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'if t \\&\\$1\c
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'if n \\&\\$1\c
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'if n \&"
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\\&\\$2 \\$3 \\$4 \\$5 \\$6 \\$7
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'.ft R
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..
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.\" @(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2
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. \" AM - accent mark definitions
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.bd B 3
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. \" fudge factors for nroff and troff
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.if t \{\
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.if n \{\
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.ds . \\k:\h'-(\\n(.wu*8/10)'\v'\*(#V*4/10'\z.\v'-\*(#V*4/10'\h'|\\n:u'
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. \" corrections for vroff
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.if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u'
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.if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u'
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. \" for low resolution devices (crt and lpr)
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.if \n(.H>23 .if \n(.V>19 \
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\{\
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. ds : e
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. ds 8 ss
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. ds v \h'-1'\o'\(aa\(ga'
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. ds . \h'-1'.
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. ds 3 3
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. ds d- d\h'-1'\(ga
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. ds D- D\h'-1'\(hy
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. ds th \o'bp'
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. ds Ae AE
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.\}
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.rm #[ #] #H #V #F C
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.SH "NAME"
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RAND_add, RAND_seed, RAND_status, RAND_event, RAND_screen \- add
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entropy to the PRNG
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.SH "LIBRARY"
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libcrypto, -lcrypto
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.SH "SYNOPSIS"
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.PP
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.Vb 1
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\& #include <openssl/rand.h>
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.Ve
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.Vb 1
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\& void RAND_seed(const void *buf, int num);
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.Ve
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.Vb 1
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\& void RAND_add(const void *buf, int num, double entropy);
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.Ve
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.Vb 1
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\& int RAND_status(void);
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.Ve
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.Vb 2
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\& int RAND_event(UINT iMsg, WPARAM wParam, LPARAM lParam);
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\& void RAND_screen(void);
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.Ve
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.SH "DESCRIPTION"
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\fIRAND_add()\fR mixes the \fBnum\fR bytes at \fBbuf\fR into the PRNG state. Thus,
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if the data at \fBbuf\fR are unpredictable to an adversary, this
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increases the uncertainty about the state and makes the PRNG output
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less predictable. Suitable input comes from user interaction (random
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key presses, mouse movements) and certain hardware events. The
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\fBentropy\fR argument is (the lower bound of) an estimate of how much
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randomness is contained in \fBbuf\fR, measured in bytes. Details about
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sources of randomness and how to estimate their entropy can be found
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in the literature, e.g. RFC 1750.
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.PP
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\fIRAND_add()\fR may be called with sensitive data such as user entered
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passwords. The seed values cannot be recovered from the PRNG output.
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.PP
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OpenSSL makes sure that the PRNG state is unique for each thread. On
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systems that provide \f(CW/dev/urandom\fR, the randomness device is used
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to seed the PRNG transparently. However, on all other systems, the
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application is responsible for seeding the PRNG by calling \fIRAND_add()\fR,
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the \fIRAND_egd(3)|RAND_egd(3)\fR manpage
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or the \fIRAND_load_file(3)|RAND_load_file(3)\fR manpage.
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.PP
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\fIRAND_seed()\fR is equivalent to \fIRAND_add()\fR when \fBnum == entropy\fR.
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.PP
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\fIRAND_event()\fR collects the entropy from Windows events such as mouse
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movements and other user interaction. It should be called with the
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\fBiMsg\fR, \fBwParam\fR and \fBlParam\fR arguments of \fIall\fR messages sent to
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the window procedure. It will estimate the entropy contained in the
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event message (if any), and add it to the PRNG. The program can then
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process the messages as usual.
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.PP
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The \fIRAND_screen()\fR function is available for the convenience of Windows
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programmers. It adds the current contents of the screen to the PRNG.
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For applications that can catch Windows events, seeding the PRNG by
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calling \fIRAND_event()\fR is a significantly better source of
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randomness. It should be noted that both methods cannot be used on
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servers that run without user interaction.
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.SH "RETURN VALUES"
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\fIRAND_status()\fR and \fIRAND_event()\fR return 1 if the PRNG has been seeded
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with enough data, 0 otherwise.
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.PP
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The other functions do not return values.
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.SH "SEE ALSO"
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the \fIrand(3)|rand(3)\fR manpage, the \fIRAND_egd(3)|RAND_egd(3)\fR manpage,
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the \fIRAND_load_file(3)|RAND_load_file(3)\fR manpage, the \fIRAND_cleanup(3)|RAND_cleanup(3)\fR manpage
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.SH "HISTORY"
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\fIRAND_seed()\fR and \fIRAND_screen()\fR are available in all versions of SSLeay
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and OpenSSL. \fIRAND_add()\fR and \fIRAND_status()\fR have been added in OpenSSL
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0.9.5, \fIRAND_event()\fR in OpenSSL 0.9.5a.
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.rn }` ''
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.IX Title "RAND_add 3"
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.IX Name "RAND_add, RAND_seed, RAND_status, RAND_event, RAND_screen - add
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entropy to the PRNG"
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.IX Header "NAME"
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.IX Header "SYNOPSIS"
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.IX Header "DESCRIPTION"
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.IX Header "RETURN VALUES"
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.IX Header "SEE ALSO"
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.IX Header "HISTORY"
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