openssl-prebuild/linux_amd64/ssl/share/man/man7/EVP_KDF-X942.7
2020-03-02 16:50:34 +00:00

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.\" ========================================================================
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.IX Title "EVP_KDF-X942 7"
.TH EVP_KDF-X942 7 "2020-03-02" "3.0.0-dev" "OpenSSL"
.\" For nroff, turn off justification. Always turn off hyphenation; it makes
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.nh
.SH "NAME"
EVP_KDF\-X942 \- The X9.42\-2001 asn1 EVP_KDF implementation
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The \s-1EVP_KDF\-X942\s0 algorithm implements the key derivation function (X942KDF).
X942KDF is used by Cryptographic Message Syntax (\s-1CMS\s0) for \s-1DH\s0 KeyAgreement, to
derive a key using input such as a shared secret key and other info. The other
info is \s-1DER\s0 encoded data that contains a 32 bit counter.
.SS "Identity"
.IX Subsection "Identity"
\&\*(L"X942KDF\*(R" is the name for this implementation; it
can be used with the \fIEVP_KDF_fetch()\fR function.
.SS "Supported parameters"
.IX Subsection "Supported parameters"
The supported parameters are:
.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>"
.PD 0
.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
These parameters work as described in \*(L"\s-1PARAMETERS\s0\*(R" in \s-1\fIEVP_KDF\s0\fR\|(3).
.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>"
The shared secret used for key derivation. This parameter sets the secret.
.ie n .IP """ukm"" (\fB\s-1OSSL_KDF_PARAM_UKM\s0\fR) <octet string>" 4
.el .IP "``ukm'' (\fB\s-1OSSL_KDF_PARAM_UKM\s0\fR) <octet string>" 4
.IX Item "ukm (OSSL_KDF_PARAM_UKM) <octet string>"
This parameter is an optional random string that is provided
by the sender called \*(L"partyAInfo\*(R".
In \s-1CMS\s0 this is the user keying material.
.ie n .IP """cekalg"" (\fB\s-1OSSL_KDF_PARAM_CEK_ALG\s0\fR) <\s-1UTF8\s0 string>" 4
.el .IP "``cekalg'' (\fB\s-1OSSL_KDF_PARAM_CEK_ALG\s0\fR) <\s-1UTF8\s0 string>" 4
.IX Item "cekalg (OSSL_KDF_PARAM_CEK_ALG) <UTF8 string>"
This parameter sets the \s-1CEK\s0 wrapping algorithm name.
.SH "NOTES"
.IX Header "NOTES"
A context for X942KDF can be obtained by calling:
.PP
.Vb 2
\& EVP_KDF *kdf = EVP_KDF_fetch(NULL, "X942KDF", NULL);
\& EVP_KDF_CTX *kctx = EVP_KDF_CTX_new(kdf);
.Ve
.PP
The output length of an X942KDF is specified via the \fIkeylen\fR
parameter to the \fIEVP_KDF_derive\fR\|(3) function.
.SH "EXAMPLES"
.IX Header "EXAMPLES"
This example derives 24 bytes, with the secret key \*(L"secret\*(R" and a random user
keying material:
.PP
.Vb 5
\& EVP_KDF_CTX *kctx;
\& EVP_KDF_CTX *kctx;
\& unsigned char out[192/8];
\& unsignred char ukm[64];
\& OSSL_PARAM params[5], *p = params;
\&
\& if (RAND_bytes(ukm, sizeof(ukm)) <= 0)
\& error("RAND_bytes");
\&
\& kdf = EVP_KDF_fetch(NULL, "X942KDF", NULL);
\& if (kctx == NULL)
\& error("EVP_KDF_fetch");
\& kctx = EVP_KDF_CTX_new(kdf);
\& if (kctx == NULL)
\& error("EVP_KDF_CTX_new");
\& EVP_KDF_free(kdf);
\&
\& *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_DIGEST,
\& SN_sha256, strlen(SN_sha256));
\& *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_SECRET,
\& "secret", (size_t)6);
\& *p++ = OSSL_PARAM_construct_octet_string(OSSL_KDF_PARAM_UKM, ukm, sizeof(ukm));
\& *p++ = OSSL_PARAM_construct_utf8_string(OSSL_KDF_PARAM_CEK_ALG,
\& SN_id_smime_alg_CMS3DESwrap,
\& strlen(SN_id_smime_alg_CMS3DESwrap));
\& *p = OSSL_PARAM_construct_end();
\& if (EVP_KDF_CTX_set_params(kctx, params) <= 0)
\& error("EVP_KDF_CTX_set_params");
\& if (EVP_KDF_derive(kctx, out, sizeof(out)) <= 0)
\& error("EVP_KDF_derive");
\&
\& EVP_KDF_CTX_free(kctx);
.Ve
.SH "CONFORMING TO"
.IX Header "CONFORMING TO"
\&\s-1RFC\s0 2631
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\s-1\fIEVP_KDF\s0\fR\|(3),
\&\fIEVP_KDF_CTX_new\fR\|(3),
\&\fIEVP_KDF_CTX_free\fR\|(3),
\&\fIEVP_KDF_CTX_set_params\fR\|(3),
\&\fIEVP_KDF_size\fR\|(3),
\&\fIEVP_KDF_derive\fR\|(3),
\&\*(L"\s-1PARAMETERS\s0\*(R" in \s-1\fIEVP_KDF\s0\fR\|(3)
.SH "HISTORY"
.IX Header "HISTORY"
This functionality was added to OpenSSL 3.0.
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2019 The OpenSSL Project Authors. All Rights Reserved.
.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>.