path: root/upstream/debian-bookworm/man7/EVP_KDF-KB.7ssl

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.\" ========================================================================
.\"
.IX Title "EVP_KDF-KB 7SSL"
.TH EVP_KDF-KB 7SSL "2023-10-23" "3.0.11" "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>.