.\" Automatically generated by Pod::Man 4.14 (Pod::Simple 3.43)
.\"
.\" 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_KDF-KB 7SSL"
.TH EVP_KDF-KB 7SSL "2024-10-27" "3.0.15" "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_KDF\-KB \- The Key\-Based EVP_KDF implementation
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The \s-1EVP_KDF\-KB\s0 algorithm implements the Key-Based key derivation function
(\s-1KBKDF\s0).  \s-1KBKDF\s0 derives a key from repeated application of a keyed \s-1MAC\s0 to an
input secret (and other optional values).
.SS "Identity"
.IX Subsection "Identity"
\&\*(L"\s-1KBKDF\*(R"\s0 is the name for this implementation; it can be used with the
\&\fBEVP_KDF_fetch()\fR function.
.SS "Supported parameters"
.IX Subsection "Supported parameters"
The supported parameters are:
.ie n .IP """mode"" (\fB\s-1OSSL_KDF_PARAM_MODE\s0\fR) <\s-1UTF8\s0 string>" 4
.el .IP "``mode'' (\fB\s-1OSSL_KDF_PARAM_MODE\s0\fR) <\s-1UTF8\s0 string>" 4
.IX Item "mode (OSSL_KDF_PARAM_MODE) <UTF8 string>"
The mode parameter determines which flavor of \s-1KBKDF\s0 to use \- currently the
choices are \*(L"counter\*(R" and \*(L"feedback\*(R". \*(L"counter\*(R" is the default, and will be
used if unspecified.
.ie n .IP """mac"" (\fB\s-1OSSL_KDF_PARAM_MAC\s0\fR) <\s-1UTF8\s0 string>" 4
.el .IP "``mac'' (\fB\s-1OSSL_KDF_PARAM_MAC\s0\fR) <\s-1UTF8\s0 string>" 4
.IX Item "mac (OSSL_KDF_PARAM_MAC) <UTF8 string>"
The value is either \s-1CMAC\s0 or \s-1HMAC.\s0
.ie n .IP """digest"" (\fB\s-1OSSL_KDF_PARAM_DIGEST\s0\fR) <\s-1UTF8\s0 string>" 4
.el .IP "``digest'' (\fB\s-1OSSL_KDF_PARAM_DIGEST\s0\fR) <\s-1UTF8\s0 string>" 4
.IX Item "digest (OSSL_KDF_PARAM_DIGEST) <UTF8 string>"
.PD 0
.ie n .IP """cipher"" (\fB\s-1OSSL_KDF_PARAM_CIPHER\s0\fR) <\s-1UTF8\s0 string>" 4
.el .IP "``cipher'' (\fB\s-1OSSL_KDF_PARAM_CIPHER\s0\fR) <\s-1UTF8\s0 string>" 4
.IX Item "cipher (OSSL_KDF_PARAM_CIPHER) <UTF8 string>"
.ie n .IP """properties"" (\fB\s-1OSSL_KDF_PARAM_PROPERTIES\s0\fR) <\s-1UTF8\s0 string>" 4
.el .IP "``properties'' (\fB\s-1OSSL_KDF_PARAM_PROPERTIES\s0\fR) <\s-1UTF8\s0 string>" 4
.IX Item "properties (OSSL_KDF_PARAM_PROPERTIES) <UTF8 string>"
.ie n .IP """key"" (\fB\s-1OSSL_KDF_PARAM_KEY\s0\fR) <octet string>" 4
.el .IP "``key'' (\fB\s-1OSSL_KDF_PARAM_KEY\s0\fR) <octet string>" 4
.IX Item "key (OSSL_KDF_PARAM_KEY) <octet string>"
.ie n .IP """salt"" (\fB\s-1OSSL_KDF_PARAM_SALT\s0\fR) <octet string>" 4
.el .IP "``salt'' (\fB\s-1OSSL_KDF_PARAM_SALT\s0\fR) <octet string>" 4
.IX Item "salt (OSSL_KDF_PARAM_SALT) <octet string>"
.IP """info (\fB\s-1OSSL_KDF_PARAM_INFO\s0\fR) <octet string>" 4
.IX Item """info (OSSL_KDF_PARAM_INFO) <octet string>"
.ie n .IP """seed"" (\fB\s-1OSSL_KDF_PARAM_SEED\s0\fR) <octet string>" 4
.el .IP "``seed'' (\fB\s-1OSSL_KDF_PARAM_SEED\s0\fR) <octet string>" 4
.IX Item "seed (OSSL_KDF_PARAM_SEED) <octet string>"
.PD
The seed parameter is unused in counter mode.
.ie n .IP """use-l"" (\fB\s-1OSSL_KDF_PARAM_KBKDF_USE_L\s0\fR) <integer>" 4
.el .IP "``use-l'' (\fB\s-1OSSL_KDF_PARAM_KBKDF_USE_L\s0\fR) <integer>" 4
.IX Item "use-l (OSSL_KDF_PARAM_KBKDF_USE_L) <integer>"
Set to \fB0\fR to disable use of the optional Fixed Input data 'L' (see \s-1SP800\-108\s0).
The default value of \fB1\fR will be used if unspecified.
.ie n .IP """use-separator"" (\fB\s-1OSSL_KDF_PARAM_KBKDF_USE_SEPARATOR\s0\fR) <integer>" 4
.el .IP "``use-separator'' (\fB\s-1OSSL_KDF_PARAM_KBKDF_USE_SEPARATOR\s0\fR) <integer>" 4
.IX Item "use-separator (OSSL_KDF_PARAM_KBKDF_USE_SEPARATOR) <integer>"
Set to \fB0\fR to disable use of the optional Fixed Input data 'zero separator'
(see \s-1SP800\-108\s0) that is placed between the Label and Context.
The default value of \fB1\fR will be used if unspecified.
.PP
Depending on whether mac is \s-1CMAC\s0 or \s-1HMAC,\s0 either digest or cipher is required
(respectively) and the other is unused.
.PP
The parameters key, salt, info, and seed correspond to \s-1KI,\s0 Label, Context, and
\&\s-1IV\s0 (respectively) in \s-1SP800\-108.\s0  As in that document, salt, info, and seed are
optional and may be omitted.
.PP
\&\*(L"mac\*(R", \*(L"digest\*(R", cipher\*(L" and \*(R"properties" are described in
\&\*(L"\s-1PARAMETERS\*(R"\s0 in \s-1\fBEVP_KDF\s0\fR\|(3).
.SH "NOTES"
.IX Header "NOTES"
A context for \s-1KBKDF\s0 can be obtained by calling:
.PP
.Vb 2
\& EVP_KDF *kdf = EVP_KDF_fetch(NULL, "KBKDF", NULL);
\& EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf);
.Ve
.PP
The output length of an \s-1KBKDF\s0 is specified via the \f(CW\*(C`keylen\*(C'\fR
parameter to the \fBEVP_KDF_derive\fR\|(3) function.
.PP
Note that currently OpenSSL only implements counter and feedback modes.  Other
variants may be supported in the future.
.SH "EXAMPLES"
.IX Header "EXAMPLES"
This example derives 10 bytes using \s-1COUNTER\-HMAC\-SHA256,\s0 with \s-1KI\s0 \*(L"secret\*(R",
Label \*(L"label\*(R", and Context \*(L"context\*(R".
.PP
.Vb 4
\& EVP_KDF *kdf;
\& EVP_KDF_CTX *kctx;
\& unsigned char out[10];
\& OSSL_PARAM params[6], *p = params;
\&
\& kdf = EVP_KDF_fetch(NULL, "KBKDF", NULL);
\& kctx = EVP_KDF_CTX_new(kdf);
\& EVP_KDF_free(kdf);
\&
\& *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST,
\&                                         "SHA2\-256", 0);
\& *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_MAC,
\&                                         "HMAC", 0);
\& *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_KEY,
\&                                          "secret", strlen("secret"));
\& *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SALT,
\&                                          "label", strlen("label"));
\& *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO,
\&                                          "context", strlen("context"));
\& *p = OSSL_PARAM_construct_end();
\& if (EVP_KDF_derive(kctx, out, sizeof(out), params) <= 0)
\&     error("EVP_KDF_derive");
\&
\& EVP_KDF_CTX_free(kctx);
.Ve
.PP
This example derives 10 bytes using \s-1FEEDBACK\-CMAC\-AES256,\s0 with \s-1KI\s0 \*(L"secret\*(R",
Label \*(L"label\*(R", and \s-1IV\s0 \*(L"sixteen bytes iv\*(R".
.PP
.Vb 5
\& EVP_KDF *kdf;
\& EVP_KDF_CTX *kctx;
\& unsigned char out[10];
\& OSSL_PARAM params[8], *p = params;
\& unsigned char *iv = "sixteen bytes iv";
\&
\& kdf = EVP_KDF_fetch(NULL, "KBKDF", NULL);
\& kctx = EVP_KDF_CTX_new(kdf);
\& EVP_KDF_free(kdf);
\&
\& *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_CIPHER, "AES256", 0);
\& *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_MAC, "CMAC", 0);
\& *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_MODE, "FEEDBACK", 0);
\& *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_KEY,
\&                                          "secret", strlen("secret"));
\& *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SALT,
\&                                          "label", strlen("label"));
\& *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_INFO,
\&                                          "context", strlen("context"));
\& *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SEED,
\&                                          iv, strlen(iv));
\& *p = OSSL_PARAM_construct_end();
\& if (EVP_KDF_derive(kctx, out, sizeof(out), params) <= 0)
\&     error("EVP_KDF_derive");
\&
\& EVP_KDF_CTX_free(kctx);
.Ve
.SH "CONFORMING TO"
.IX Header "CONFORMING TO"
\&\s-1NIST SP800\-108, IETF RFC 6803, IETF RFC 8009.\s0
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\s-1\fBEVP_KDF\s0\fR\|(3),
\&\fBEVP_KDF_CTX_free\fR\|(3),
\&\fBEVP_KDF_CTX_get_kdf_size\fR\|(3),
\&\fBEVP_KDF_derive\fR\|(3),
\&\*(L"\s-1PARAMETERS\*(R"\s0 in \s-1\fBEVP_KDF\s0\fR\|(3)
.SH "HISTORY"
.IX Header "HISTORY"
This functionality was added in OpenSSL 3.0.
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2019\-2021 The OpenSSL Project Authors. All Rights Reserved.
Copyright 2019 Red Hat, Inc.
.PP
Licensed under the Apache License 2.0 (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>.
