NetBSD/lib/libcrypto/man/RAND_add.3

277 lines
7.2 KiB
Groff

.rn '' }`
'''
'''
.de Sh
.br
.if t .Sp
.ne 5
.PP
\fB\\$1\fR
.PP
..
.de Sp
.if t .sp .5v
.if n .sp
..
.de Ip
.br
.ie \\n(.$>=3 .ne \\$3
.el .ne 3
.IP "\\$1" \\$2
..
.de Vb
.ft CW
.nf
.ne \\$1
..
.de Ve
.ft R
.fi
..
'''
'''
''' Set up \*(-- to give an unbreakable dash;
''' string Tr holds user defined translation string.
''' Bell System Logo is used as a dummy character.
'''
.tr \(*W-|\(bv\*(Tr
.ie n \{\
.ds -- \(*W-
.ds PI pi
.if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch
.if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch
.ds L" ""
.ds R" ""
''' \*(M", \*(S", \*(N" and \*(T" are the equivalent of
''' \*(L" and \*(R", except that they are used on ".xx" lines,
''' such as .IP and .SH, which do another additional levels of
''' double-quote interpretation
.ds M" """
.ds S" """
.ds N" """""
.ds T" """""
.ds L' '
.ds R' '
.ds M' '
.ds S' '
.ds N' '
.ds T' '
'br\}
.el\{\
.ds -- \(em\|
.tr \*(Tr
.ds L" ``
.ds R" ''
.ds M" ``
.ds S" ''
.ds N" ``
.ds T" ''
.ds L' `
.ds R' '
.ds M' `
.ds S' '
.ds N' `
.ds T' '
.ds PI \(*p
'br\}
.\" If the F register is turned on, we'll generate
.\" index entries out stderr for the following things:
.\" TH Title
.\" SH Header
.\" Sh Subsection
.\" Ip Item
.\" X<> Xref (embedded
.\" Of course, you have to process the output yourself
.\" in some meaninful fashion.
.if \nF \{
.de IX
.tm Index:\\$1\t\\n%\t"\\$2"
..
.nr % 0
.rr F
.\}
.TH RAND_add 3 "0.9.5a" "22/Jul/2000" "OpenSSL"
.UC
.if n .hy 0
.if n .na
.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p'
.de CQ \" put $1 in typewriter font
.ft CW
'if n "\c
'if t \\&\\$1\c
'if n \\&\\$1\c
'if n \&"
\\&\\$2 \\$3 \\$4 \\$5 \\$6 \\$7
'.ft R
..
.\" @(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2
. \" AM - accent mark definitions
.bd B 3
. \" fudge factors for nroff and troff
.if n \{\
. ds #H 0
. ds #V .8m
. ds #F .3m
. ds #[ \f1
. ds #] \fP
.\}
.if t \{\
. ds #H ((1u-(\\\\n(.fu%2u))*.13m)
. ds #V .6m
. ds #F 0
. ds #[ \&
. ds #] \&
.\}
. \" simple accents for nroff and troff
.if n \{\
. ds ' \&
. ds ` \&
. ds ^ \&
. ds , \&
. ds ~ ~
. ds ? ?
. ds ! !
. ds /
. ds q
.\}
.if t \{\
. ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u"
. ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u'
. ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u'
. ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u'
. ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u'
. ds ? \s-2c\h'-\w'c'u*7/10'\u\h'\*(#H'\zi\d\s+2\h'\w'c'u*8/10'
. ds ! \s-2\(or\s+2\h'-\w'\(or'u'\v'-.8m'.\v'.8m'
. ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u'
. ds q o\h'-\w'o'u*8/10'\s-4\v'.4m'\z\(*i\v'-.4m'\s+4\h'\w'o'u*8/10'
.\}
. \" troff and (daisy-wheel) nroff accents
.ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V'
.ds 8 \h'\*(#H'\(*b\h'-\*(#H'
.ds v \\k:\h'-(\\n(.wu*9/10-\*(#H)'\v'-\*(#V'\*(#[\s-4v\s0\v'\*(#V'\h'|\\n:u'\*(#]
.ds _ \\k:\h'-(\\n(.wu*9/10-\*(#H+(\*(#F*2/3))'\v'-.4m'\z\(hy\v'.4m'\h'|\\n:u'
.ds . \\k:\h'-(\\n(.wu*8/10)'\v'\*(#V*4/10'\z.\v'-\*(#V*4/10'\h'|\\n:u'
.ds 3 \*(#[\v'.2m'\s-2\&3\s0\v'-.2m'\*(#]
.ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#]
.ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H'
.ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u'
.ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#]
.ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#]
.ds ae a\h'-(\w'a'u*4/10)'e
.ds Ae A\h'-(\w'A'u*4/10)'E
.ds oe o\h'-(\w'o'u*4/10)'e
.ds Oe O\h'-(\w'O'u*4/10)'E
. \" corrections for vroff
.if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u'
.if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u'
. \" for low resolution devices (crt and lpr)
.if \n(.H>23 .if \n(.V>19 \
\{\
. ds : e
. ds 8 ss
. ds v \h'-1'\o'\(aa\(ga'
. ds _ \h'-1'^
. ds . \h'-1'.
. ds 3 3
. ds o a
. ds d- d\h'-1'\(ga
. ds D- D\h'-1'\(hy
. ds th \o'bp'
. ds Th \o'LP'
. ds ae ae
. ds Ae AE
. ds oe oe
. ds Oe OE
.\}
.rm #[ #] #H #V #F C
.SH "NAME"
RAND_add, RAND_seed, RAND_status, RAND_event, RAND_screen \- add
entropy to the PRNG
.SH "LIBRARY"
libcrypto, -lcrypto
.SH "SYNOPSIS"
.PP
.Vb 1
\& #include <openssl/rand.h>
.Ve
.Vb 1
\& void RAND_seed(const void *buf, int num);
.Ve
.Vb 1
\& void RAND_add(const void *buf, int num, double entropy);
.Ve
.Vb 1
\& int RAND_status(void);
.Ve
.Vb 2
\& int RAND_event(UINT iMsg, WPARAM wParam, LPARAM lParam);
\& void RAND_screen(void);
.Ve
.SH "DESCRIPTION"
\fIRAND_add()\fR mixes the \fBnum\fR bytes at \fBbuf\fR into the PRNG state. Thus,
if the data at \fBbuf\fR are unpredictable to an adversary, this
increases the uncertainty about the state and makes the PRNG output
less predictable. Suitable input comes from user interaction (random
key presses, mouse movements) and certain hardware events. The
\fBentropy\fR argument is (the lower bound of) an estimate of how much
randomness is contained in \fBbuf\fR, measured in bytes. Details about
sources of randomness and how to estimate their entropy can be found
in the literature, e.g. RFC 1750.
.PP
\fIRAND_add()\fR may be called with sensitive data such as user entered
passwords. The seed values cannot be recovered from the PRNG output.
.PP
OpenSSL makes sure that the PRNG state is unique for each thread. On
systems that provide \f(CW/dev/urandom\fR, the randomness device is used
to seed the PRNG transparently. However, on all other systems, the
application is responsible for seeding the PRNG by calling \fIRAND_add()\fR,
the \fIRAND_egd(3)|RAND_egd(3)\fR manpage
or the \fIRAND_load_file(3)|RAND_load_file(3)\fR manpage.
.PP
\fIRAND_seed()\fR is equivalent to \fIRAND_add()\fR when \fBnum == entropy\fR.
.PP
\fIRAND_event()\fR collects the entropy from Windows events such as mouse
movements and other user interaction. It should be called with the
\fBiMsg\fR, \fBwParam\fR and \fBlParam\fR arguments of \fIall\fR messages sent to
the window procedure. It will estimate the entropy contained in the
event message (if any), and add it to the PRNG. The program can then
process the messages as usual.
.PP
The \fIRAND_screen()\fR function is available for the convenience of Windows
programmers. It adds the current contents of the screen to the PRNG.
For applications that can catch Windows events, seeding the PRNG by
calling \fIRAND_event()\fR is a significantly better source of
randomness. It should be noted that both methods cannot be used on
servers that run without user interaction.
.SH "RETURN VALUES"
\fIRAND_status()\fR and \fIRAND_event()\fR return 1 if the PRNG has been seeded
with enough data, 0 otherwise.
.PP
The other functions do not return values.
.SH "SEE ALSO"
the \fIrand(3)|rand(3)\fR manpage, the \fIRAND_egd(3)|RAND_egd(3)\fR manpage,
the \fIRAND_load_file(3)|RAND_load_file(3)\fR manpage, the \fIRAND_cleanup(3)|RAND_cleanup(3)\fR manpage
.SH "HISTORY"
\fIRAND_seed()\fR and \fIRAND_screen()\fR are available in all versions of SSLeay
and OpenSSL. \fIRAND_add()\fR and \fIRAND_status()\fR have been added in OpenSSL
0.9.5, \fIRAND_event()\fR in OpenSSL 0.9.5a.
.rn }` ''
.IX Title "RAND_add 3"
.IX Name "RAND_add, RAND_seed, RAND_status, RAND_event, RAND_screen - add
entropy to the PRNG"
.IX Header "NAME"
.IX Header "SYNOPSIS"
.IX Header "DESCRIPTION"
.IX Header "RETURN VALUES"
.IX Header "SEE ALSO"
.IX Header "HISTORY"