#$@%#$%!

Ngiler SH3LL 360
: / opt / cpanel / ea-openssl11 / share / man / man3 /

Information Server
MySQL : OFF Perl : OFF CURL : ON WGET : OFF PKEXEC : OFF

Directive	Local Value
IP Address	162.0.209.101
System	Linux premium169.web-hosting.com 4.18.0-553.50.1.lve.el8.x86_64 #1 SMP Thu Apr 17 19:10:24 UTC 2025 x86_64
User	luxeelil
PHP Version	8.0.30
Software	LiteSpeed
Doc root	Writable

Edit File : EVP_PKEY_CTX_set_hkdf_md.3 \| Size : 10.38 KB
.\" 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(.wu8/10-\(#H)'\'\h"\|\\n:u" . ds ` \\k:\h'-(\\n(.wu8/10-\(#H)'\`\h'\|\\n:u' . ds ^ \\k:\h'-(\\n(.wu10/11-\(#H)'^\h'\|\\n:u' . ds , \\k:\h'-(\\n(.wu8/10)',\h'\|\\n:u' . ds ~ \\k:\h'-(\\n(.wu-\(#H-.1m)'~\h'\|\\n:u' . ds / \\k:\h'-(\\n(.wu8/10-\(#H)'\z\(sl\h'\|\\n:u' .\} . \" troff and (daisy-wheel) nroff accents .ds : \\k:\h'-(\\n(.wu8/10-\(#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'u2/3)'\s-1o\s+1\(#] .ds Th \(#[\s+2I\s-2\h'-\w'I'u3/5'\v'-.3m'o\v'.3m'\(#] .ds ae a\h'-(\w'a'u4/10)'e .ds Ae A\h'-(\w'A'u4/10)'E . \" corrections for vroff .if v .ds ~ \\k:\h'-(\\n(.wu9/10-\(#H)'\s-2\u~\d\s+2\h'\|\\n:u' .if v .ds ^ \\k:\h'-(\\n(.wu10/11-\(#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_PKEY_CTX_SET_HKDF_MD 3" .TH EVP_PKEY_CTX_SET_HKDF_MD 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_PKEY_CTX_set_hkdf_md, EVP_PKEY_CTX_set1_hkdf_salt, EVP_PKEY_CTX_set1_hkdf_key, EVP_PKEY_CTX_add1_hkdf_info, EVP_PKEY_CTX_hkdf_mode \- HMAC\-based Extract\-and\-Expand key derivation algorithm .SH "SYNOPSIS" .IX Header "SYNOPSIS" .Vb 1 \& #include <openssl/kdf.h> \& \& int EVP_PKEY_CTX_hkdf_mode(EVP_PKEY_CTX pctx, int mode); \& \& int EVP_PKEY_CTX_set_hkdf_md(EVP_PKEY_CTX pctx, const EVP_MD md); \& \& int EVP_PKEY_CTX_set1_hkdf_salt(EVP_PKEY_CTX pctx, unsigned char salt, \& int saltlen); \& \& int EVP_PKEY_CTX_set1_hkdf_key(EVP_PKEY_CTX pctx, unsigned char key, \& int keylen); \& \& int EVP_PKEY_CTX_add1_hkdf_info(EVP_PKEY_CTX pctx, unsigned char info, \& int infolen); .Ve .SH "DESCRIPTION" .IX Header "DESCRIPTION" The \s-1EVP_PKEY_HKDF\s0 algorithm implements the \s-1HKDF\s0 key derivation function. \&\s-1HKDF\s0 follows the \(L"extract-then-expand\(R" paradigm, where the \s-1KDF\s0 logically consists of two modules. The first stage takes the input keying material and \(L"extracts\(R" from it a fixed-length pseudorandom key K. The second stage \&\(L"expands\(R" the key K into several additional pseudorandom keys (the output of the \s-1KDF\s0). .PP \&\fBEVP_PKEY_CTX_hkdf_mode()\fR sets the mode for the \s-1HKDF\s0 operation. There are three modes that are currently defined: .IP "\s-1EVP_PKEY_HKDEF_MODE_EXTRACT_AND_EXPAND\s0" 4 .IX Item "EVP_PKEY_HKDEF_MODE_EXTRACT_AND_EXPAND" This is the default mode. Calling \fBEVP_PKEY_derive\fR\\|(3) on an \s-1EVP_PKEY_CTX\s0 set up for \s-1HKDF\s0 will perform an extract followed by an expand operation in one go. The derived key returned will be the result after the expand operation. The intermediate fixed-length pseudorandom key K is not returned. .Sp In this mode the digest, key, salt and info values must be set before a key is derived or an error occurs. .IP "\s-1EVP_PKEY_HKDEF_MODE_EXTRACT_ONLY\s0" 4 .IX Item "EVP_PKEY_HKDEF_MODE_EXTRACT_ONLY" In this mode calling \fBEVP_PKEY_derive\fR\\|(3) will just perform the extract operation. The value returned will be the intermediate fixed-length pseudorandom key K. .Sp The digest, key and salt values must be set before a key is derived or an error occurs. .IP "\s-1EVP_PKEY_HKDEF_MODE_EXPAND_ONLY\s0" 4 .IX Item "EVP_PKEY_HKDEF_MODE_EXPAND_ONLY" In this mode calling \fBEVP_PKEY_derive\fR\\|(3) will just perform the expand operation. The input key should be set to the intermediate fixed-length pseudorandom key K returned from a previous extract operation. .Sp The digest, key and info values must be set before a key is derived or an error occurs. .PP \&\fBEVP_PKEY_CTX_set_hkdf_md()\fR sets the message digest associated with the \s-1HKDF.\s0 .PP \&\fBEVP_PKEY_CTX_set1_hkdf_salt()\fR sets the salt to \fBsaltlen\fR bytes of the buffer \fBsalt\fR. Any existing value is replaced. .PP \&\fBEVP_PKEY_CTX_set1_hkdf_key()\fR sets the key to \fBkeylen\fR bytes of the buffer \&\fBkey\fR. Any existing value is replaced. .PP \&\fBEVP_PKEY_CTX_add1_hkdf_info()\fR sets the info value to \fBinfolen\fR bytes of the buffer \fBinfo\fR. If a value is already set, it is appended to the existing value. .SH "STRING CTRLS" .IX Header "STRING CTRLS" \&\s-1HKDF\s0 also supports string based control operations via \&\fBEVP_PKEY_CTX_ctrl_str\fR\\|(3). The \fBtype\fR parameter \(L"md\(R" uses the supplied \fBvalue\fR as the name of the digest algorithm to use. The \fBtype\fR parameter \(L"mode\(R" uses the values \(L"\s-1EXTRACT_AND_EXPAND\(R", \&\(L"EXTRACT_ONLY\(R"\s0 and \(L"\s-1EXPAND_ONLY\(R"\s0 to determine the mode to use. The \fBtype\fR parameters \(L"salt\(R", \(L"key\(R" and \(L"info\(R" use the supplied \fBvalue\fR parameter as a \fBseed\fR, \fBkey\fR or \fBinfo\fR value. The names \(L"hexsalt\(R", \(L"hexkey\(R" and \(L"hexinfo\(R" are similar except they take a hex string which is converted to binary. .SH "NOTES" .IX Header "NOTES" All these functions are implemented as macros. .PP A context for \s-1HKDF\s0 can be obtained by calling: .PP .Vb 1 \& EVP_PKEY_CTX pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_HKDF, NULL); .Ve .PP The total length of the info buffer cannot exceed 1024 bytes in length: this should be more than enough for any normal use of \s-1HKDF.\s0 .PP The output length of an \s-1HKDF\s0 expand operation is specified via the length parameter to the \fBEVP_PKEY_derive\fR\\|(3) function. Since the \s-1HKDF\s0 output length is variable, passing a \fB\s-1NULL\s0\fR buffer as a means to obtain the requisite length is not meaningful with \s-1HKDF\s0 in any mode that performs an expand operation. Instead, the caller must allocate a buffer of the desired length, and pass that buffer to \fBEVP_PKEY_derive\fR\\|(3) along with (a pointer initialized to) the desired length. Passing a \fB\s-1NULL\s0\fR buffer to obtain the length is allowed when using \s-1EVP_PKEY_HKDEF_MODE_EXTRACT_ONLY.\s0 .PP Optimised versions of \s-1HKDF\s0 can be implemented in an \s-1ENGINE.\s0 .SH "RETURN VALUES" .IX Header "RETURN VALUES" All these functions return 1 for success and 0 or a negative value for failure. In particular a return value of \-2 indicates the operation is not supported by the public key algorithm. .SH "EXAMPLES" .IX Header "EXAMPLES" This example derives 10 bytes using \s-1SHA\-256\s0 with the secret key \(L"secret\(R", salt value \(L"salt\(R" and info value \(L"label\(R": .PP .Vb 4 \& EVP_PKEY_CTX pctx; \& unsigned char out[10]; \& size_t outlen = sizeof(out); \& pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_HKDF, NULL); \& \& if (EVP_PKEY_derive_init(pctx) <= 0) \& /* Error / \& if (EVP_PKEY_CTX_set_hkdf_md(pctx, EVP_sha256()) <= 0) \& / Error / \& if (EVP_PKEY_CTX_set1_hkdf_salt(pctx, "salt", 4) <= 0) \& / Error / \& if (EVP_PKEY_CTX_set1_hkdf_key(pctx, "secret", 6) <= 0) \& / Error / \& if (EVP_PKEY_CTX_add1_hkdf_info(pctx, "label", 5) <= 0) \& / Error / \& if (EVP_PKEY_derive(pctx, out, &outlen) <= 0) \& / Error / .Ve .SH "CONFORMING TO" .IX Header "CONFORMING TO" \&\s-1RFC 5869\s0 .SH "SEE ALSO" .IX Header "SEE ALSO" \&\fBEVP_PKEY_CTX_new\fR\\|(3), \&\fBEVP_PKEY_CTX_ctrl_str\fR\\|(3), \&\fBEVP_PKEY_derive\fR\\|(3) .SH "COPYRIGHT" .IX Header "COPYRIGHT" Copyright 2016\-2019 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>. Back

Edit File : EVP_PKEY_CTX_set_hkdf_md.3 | Size : 10.38 KB

.\" 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_PKEY_CTX_SET_HKDF_MD 3"
.TH EVP_PKEY_CTX_SET_HKDF_MD 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_PKEY_CTX_set_hkdf_md, EVP_PKEY_CTX_set1_hkdf_salt, EVP_PKEY_CTX_set1_hkdf_key, EVP_PKEY_CTX_add1_hkdf_info, EVP_PKEY_CTX_hkdf_mode \- HMAC\-based Extract\-and\-Expand key derivation algorithm
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/kdf.h>
\&
\& int EVP_PKEY_CTX_hkdf_mode(EVP_PKEY_CTX *pctx, int mode);
\&
\& int EVP_PKEY_CTX_set_hkdf_md(EVP_PKEY_CTX *pctx, const EVP_MD *md);
\&
\& int EVP_PKEY_CTX_set1_hkdf_salt(EVP_PKEY_CTX *pctx, unsigned char *salt,
\&                                 int saltlen);
\&
\& int EVP_PKEY_CTX_set1_hkdf_key(EVP_PKEY_CTX *pctx, unsigned char *key,
\&                                int keylen);
\&
\& int EVP_PKEY_CTX_add1_hkdf_info(EVP_PKEY_CTX *pctx, unsigned char *info,
\&                                 int infolen);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The \s-1EVP_PKEY_HKDF\s0 algorithm implements the \s-1HKDF\s0 key derivation function.
\&\s-1HKDF\s0 follows the \*(L"extract-then-expand\*(R" paradigm, where the \s-1KDF\s0 logically
consists of two modules. The first stage takes the input keying material
and \*(L"extracts\*(R" from it a fixed-length pseudorandom key K. The second stage
\&\*(L"expands\*(R" the key K into several additional pseudorandom keys (the output
of the \s-1KDF\s0).
.PP
\&\fBEVP_PKEY_CTX_hkdf_mode()\fR sets the mode for the \s-1HKDF\s0 operation. There are three
modes that are currently defined:
.IP "\s-1EVP_PKEY_HKDEF_MODE_EXTRACT_AND_EXPAND\s0" 4
.IX Item "EVP_PKEY_HKDEF_MODE_EXTRACT_AND_EXPAND"
This is the default mode. Calling \fBEVP_PKEY_derive\fR\|(3) on an \s-1EVP_PKEY_CTX\s0 set
up for \s-1HKDF\s0 will perform an extract followed by an expand operation in one go.
The derived key returned will be the result after the expand operation. The
intermediate fixed-length pseudorandom key K is not returned.
.Sp
In this mode the digest, key, salt and info values must be set before a key is
derived or an error occurs.
.IP "\s-1EVP_PKEY_HKDEF_MODE_EXTRACT_ONLY\s0" 4
.IX Item "EVP_PKEY_HKDEF_MODE_EXTRACT_ONLY"
In this mode calling \fBEVP_PKEY_derive\fR\|(3) will just perform the extract
operation. The value returned will be the intermediate fixed-length pseudorandom
key K.
.Sp
The digest, key and salt values must be set before a key is derived or an
error occurs.
.IP "\s-1EVP_PKEY_HKDEF_MODE_EXPAND_ONLY\s0" 4
.IX Item "EVP_PKEY_HKDEF_MODE_EXPAND_ONLY"
In this mode calling \fBEVP_PKEY_derive\fR\|(3) will just perform the expand
operation. The input key should be set to the intermediate fixed-length
pseudorandom key K returned from a previous extract operation.
.Sp
The digest, key and info values must be set before a key is derived or an
error occurs.
.PP
\&\fBEVP_PKEY_CTX_set_hkdf_md()\fR sets the message digest associated with the \s-1HKDF.\s0
.PP
\&\fBEVP_PKEY_CTX_set1_hkdf_salt()\fR sets the salt to \fBsaltlen\fR bytes of the
buffer \fBsalt\fR. Any existing value is replaced.
.PP
\&\fBEVP_PKEY_CTX_set1_hkdf_key()\fR sets the key to \fBkeylen\fR bytes of the buffer
\&\fBkey\fR. Any existing value is replaced.
.PP
\&\fBEVP_PKEY_CTX_add1_hkdf_info()\fR sets the info value to \fBinfolen\fR bytes of the
buffer \fBinfo\fR. If a value is already set, it is appended to the existing
value.
.SH "STRING CTRLS"
.IX Header "STRING CTRLS"
\&\s-1HKDF\s0 also supports string based control operations via
\&\fBEVP_PKEY_CTX_ctrl_str\fR\|(3).
The \fBtype\fR parameter \*(L"md\*(R" uses the supplied \fBvalue\fR as the name of the digest
algorithm to use.
The \fBtype\fR parameter \*(L"mode\*(R" uses the values \*(L"\s-1EXTRACT_AND_EXPAND\*(R",
\&\*(L"EXTRACT_ONLY\*(R"\s0 and \*(L"\s-1EXPAND_ONLY\*(R"\s0 to determine the mode to use.
The \fBtype\fR parameters \*(L"salt\*(R", \*(L"key\*(R" and \*(L"info\*(R" use the supplied \fBvalue\fR
parameter as a \fBseed\fR, \fBkey\fR or \fBinfo\fR value.
The names \*(L"hexsalt\*(R", \*(L"hexkey\*(R" and \*(L"hexinfo\*(R" are similar except they take a hex
string which is converted to binary.
.SH "NOTES"
.IX Header "NOTES"
All these functions are implemented as macros.
.PP
A context for \s-1HKDF\s0 can be obtained by calling:
.PP
.Vb 1
\& EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_HKDF, NULL);
.Ve
.PP
The total length of the info buffer cannot exceed 1024 bytes in length: this
should be more than enough for any normal use of \s-1HKDF.\s0
.PP
The output length of an \s-1HKDF\s0 expand operation is specified via the length
parameter to the \fBEVP_PKEY_derive\fR\|(3) function.
Since the \s-1HKDF\s0 output length is variable, passing a \fB\s-1NULL\s0\fR buffer as a means
to obtain the requisite length is not meaningful with \s-1HKDF\s0 in any mode that
performs an expand operation. Instead, the caller must allocate a buffer of the
desired length, and pass that buffer to \fBEVP_PKEY_derive\fR\|(3) along with (a
pointer initialized to) the desired length. Passing a \fB\s-1NULL\s0\fR buffer to obtain
the length is allowed when using \s-1EVP_PKEY_HKDEF_MODE_EXTRACT_ONLY.\s0
.PP
Optimised versions of \s-1HKDF\s0 can be implemented in an \s-1ENGINE.\s0
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
All these functions return 1 for success and 0 or a negative value for failure.
In particular a return value of \-2 indicates the operation is not supported by
the public key algorithm.
.SH "EXAMPLES"
.IX Header "EXAMPLES"
This example derives 10 bytes using \s-1SHA\-256\s0 with the secret key \*(L"secret\*(R",
salt value \*(L"salt\*(R" and info value \*(L"label\*(R":
.PP
.Vb 4
\& EVP_PKEY_CTX *pctx;
\& unsigned char out[10];
\& size_t outlen = sizeof(out);
\& pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_HKDF, NULL);
\&
\& if (EVP_PKEY_derive_init(pctx) <= 0)
\&     /* Error */
\& if (EVP_PKEY_CTX_set_hkdf_md(pctx, EVP_sha256()) <= 0)
\&     /* Error */
\& if (EVP_PKEY_CTX_set1_hkdf_salt(pctx, "salt", 4) <= 0)
\&     /* Error */
\& if (EVP_PKEY_CTX_set1_hkdf_key(pctx, "secret", 6) <= 0)
\&     /* Error */
\& if (EVP_PKEY_CTX_add1_hkdf_info(pctx, "label", 5) <= 0)
\&     /* Error */
\& if (EVP_PKEY_derive(pctx, out, &outlen) <= 0)
\&     /* Error */
.Ve
.SH "CONFORMING TO"
.IX Header "CONFORMING TO"
\&\s-1RFC 5869\s0
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBEVP_PKEY_CTX_new\fR\|(3),
\&\fBEVP_PKEY_CTX_ctrl_str\fR\|(3),
\&\fBEVP_PKEY_derive\fR\|(3)
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2016\-2019 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>.

Back