????
Your IP : 18.227.13.119
.\" Automatically generated by Pod::Man 4.11 (Pod::Simple 3.35)
.\"
.\" Standard preamble:
.\" ========================================================================
.de Sp \" Vertical space (when we can't use .PP)
.if t .sp .5v
.if n .sp
..
.de Vb \" Begin verbatim text
.ft CW
.nf
.ne \\$1
..
.de Ve \" End verbatim text
.ft R
.fi
..
.\" Set up some character translations and predefined strings. \*(-- will
.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left
.\" double quote, and \*(R" will give a right double quote. \*(C+ will
.\" give a nicer C++. Capital omega is used to do unbreakable dashes and
.\" therefore won't be available. \*(C` and \*(C' expand to `' in nroff,
.\" nothing in troff, for use with C<>.
.tr \(*W-
.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p'
.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" ""
. ds C` ""
. ds C' ""
'br\}
.el\{\
. ds -- \|\(em\|
. ds PI \(*p
. ds L" ``
. ds R" ''
. ds C`
. ds C'
'br\}
.\"
.\" Escape single quotes in literal strings from groff's Unicode transform.
.ie \n(.g .ds Aq \(aq
.el .ds Aq '
.\"
.\" If the F register is >0, we'll generate index entries on stderr for
.\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index
.\" entries marked with X<> in POD. Of course, you'll have to process the
.\" output yourself in some meaningful fashion.
.\"
.\" Avoid warning from groff about undefined register 'F'.
.de IX
..
.nr rF 0
.if \n(.g .if rF .nr rF 1
.if (\n(rF:(\n(.g==0)) \{\
. if \nF \{\
. de IX
. tm Index:\\$1\t\\n%\t"\\$2"
..
. if !\nF==2 \{\
. nr % 0
. nr F 2
. \}
. \}
.\}
.rr rF
.\"
.\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2).
.\" Fear. Run. Save yourself. No user-serviceable parts.
. \" 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 /
.\}
.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 / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u'
.\}
. \" 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 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
. \" 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 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
.\}
.rm #[ #] #H #V #F C
.\" ========================================================================
.\"
.IX Title "EVP_BYTESTOKEY 3"
.TH EVP_BYTESTOKEY 3 "2023-09-11" "1.1.1w" "OpenSSL"
.\" For nroff, turn off justification. Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
EVP_BytesToKey \- password based encryption routine
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/evp.h>
\&
\& int EVP_BytesToKey(const EVP_CIPHER *type, const EVP_MD *md,
\& const unsigned char *salt,
\& const unsigned char *data, int datal, int count,
\& unsigned char *key, unsigned char *iv);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fBEVP_BytesToKey()\fR derives a key and \s-1IV\s0 from various parameters. \fBtype\fR is
the cipher to derive the key and \s-1IV\s0 for. \fBmd\fR is the message digest to use.
The \fBsalt\fR parameter is used as a salt in the derivation: it should point to
an 8 byte buffer or \s-1NULL\s0 if no salt is used. \fBdata\fR is a buffer containing
\&\fBdatal\fR bytes which is used to derive the keying data. \fBcount\fR is the
iteration count to use. The derived key and \s-1IV\s0 will be written to \fBkey\fR
and \fBiv\fR respectively.
.SH "NOTES"
.IX Header "NOTES"
A typical application of this function is to derive keying material for an
encryption algorithm from a password in the \fBdata\fR parameter.
.PP
Increasing the \fBcount\fR parameter slows down the algorithm which makes it
harder for an attacker to perform a brute force attack using a large number
of candidate passwords.
.PP
If the total key and \s-1IV\s0 length is less than the digest length and
\&\fB\s-1MD5\s0\fR is used then the derivation algorithm is compatible with PKCS#5 v1.5
otherwise a non standard extension is used to derive the extra data.
.PP
Newer applications should use a more modern algorithm such as \s-1PBKDF2\s0 as
defined in PKCS#5v2.1 and provided by \s-1PKCS5_PBKDF2_HMAC.\s0
.SH "KEY DERIVATION ALGORITHM"
.IX Header "KEY DERIVATION ALGORITHM"
The key and \s-1IV\s0 is derived by concatenating D_1, D_2, etc until
enough data is available for the key and \s-1IV.\s0 D_i is defined as:
.PP
.Vb 1
\& D_i = HASH^count(D_(i\-1) || data || salt)
.Ve
.PP
where || denotes concatenation, D_0 is empty, \s-1HASH\s0 is the digest
algorithm in use, HASH^1(data) is simply \s-1HASH\s0(data), HASH^2(data)
is \s-1HASH\s0(\s-1HASH\s0(data)) and so on.
.PP
The initial bytes are used for the key and the subsequent bytes for
the \s-1IV.\s0
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
If \fBdata\fR is \s-1NULL,\s0 then \fBEVP_BytesToKey()\fR returns the number of bytes
needed to store the derived key.
Otherwise, \fBEVP_BytesToKey()\fR returns the size of the derived key in bytes,
or 0 on error.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBevp\fR\|(7), \fBRAND_bytes\fR\|(3),
\&\s-1\fBPKCS5_PBKDF2_HMAC\s0\fR\|(3),
\&\fBEVP_EncryptInit\fR\|(3)
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2001\-2016 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the OpenSSL license (the \*(L"License\*(R"). You may not use
this file except in compliance with the License. You can obtain a copy
in the file \s-1LICENSE\s0 in the source distribution or at
<https://www.openssl.org/source/license.html>.