Android_verify/third_party/android-libs/share/man/man7/EVP_KDF-KB.7ossl

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.\" ========================================================================
.\"
.IX Title "EVP_KDF-KB 7ossl"
.TH EVP_KDF-KB 7ossl "2024-09-03" "3.3.2" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.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, HMAC, KMAC128\s0 or \s-1KMAC256.\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.
.ie n .IP """r"" (\fB\s-1OSSL_KDF_PARAM_KBKDF_R\s0\fR) <integer>" 4
.el .IP "``r'' (\fB\s-1OSSL_KDF_PARAM_KBKDF_R\s0\fR) <integer>" 4
.IX Item "r (OSSL_KDF_PARAM_KBKDF_R) <integer>"
Set the fixed value 'r', indicating the length of the counter in bits.
.Sp
Supported values are \fB8\fR, \fB16\fR, \fB24\fR, and \fB32\fR.
The default value of \fB32\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. They are unused for \s-1KMAC128\s0 and \s-1KMAC256.\s0
.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.
.PP
Support for \s-1KMAC\s0 was added in OpenSSL 3.1.
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2019\-2022 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>.