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.\" ========================================================================
.\"
.IX Title "EVP_PKEY_CTX_NEW 3ossl"
.TH EVP_PKEY_CTX_NEW 3ossl "2023-09-19" "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_PKEY_CTX_new, EVP_PKEY_CTX_new_id, EVP_PKEY_CTX_new_from_name,
EVP_PKEY_CTX_new_from_pkey, EVP_PKEY_CTX_dup, EVP_PKEY_CTX_free,
EVP_PKEY_CTX_is_a
\&\- public key algorithm context functions
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/evp.h>
\&
\& EVP_PKEY_CTX *EVP_PKEY_CTX_new(EVP_PKEY *pkey, ENGINE *e);
\& EVP_PKEY_CTX *EVP_PKEY_CTX_new_id(int id, ENGINE *e);
\& EVP_PKEY_CTX *EVP_PKEY_CTX_new_from_name(OSSL_LIB_CTX *libctx,
\& const char *name,
\& const char *propquery);
\& EVP_PKEY_CTX *EVP_PKEY_CTX_new_from_pkey(OSSL_LIB_CTX *libctx,
\& EVP_PKEY *pkey,
\& const char *propquery);
\& EVP_PKEY_CTX *EVP_PKEY_CTX_dup(const EVP_PKEY_CTX *ctx);
\& void EVP_PKEY_CTX_free(EVP_PKEY_CTX *ctx);
\& int EVP_PKEY_CTX_is_a(EVP_PKEY_CTX *ctx, const char *keytype);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The \fBEVP_PKEY_CTX_new()\fR function allocates public key algorithm context using
the \fIpkey\fR key type and \s-1ENGINE\s0 \fIe\fR.
.PP
The \fBEVP_PKEY_CTX_new_id()\fR function allocates public key algorithm context
using the key type specified by \fIid\fR and \s-1ENGINE\s0 \fIe\fR.
.PP
The \fBEVP_PKEY_CTX_new_from_name()\fR function allocates a public key algorithm
context using the library context \fIlibctx\fR (see \s-1\fBOSSL_LIB_CTX\s0\fR\|(3)), the
key type specified by \fIname\fR and the property query \fIpropquery\fR. None
of the arguments are duplicated, so they must remain unchanged for the
lifetime of the returned \fB\s-1EVP_PKEY_CTX\s0\fR or of any of its duplicates. Read
further about the possible names in \*(L"\s-1NOTES\*(R"\s0 below.
.PP
The \fBEVP_PKEY_CTX_new_from_pkey()\fR function allocates a public key algorithm
context using the library context \fIlibctx\fR (see \s-1\fBOSSL_LIB_CTX\s0\fR\|(3)) and the
algorithm specified by \fIpkey\fR and the property query \fIpropquery\fR. None of the
arguments are duplicated, so they must remain unchanged for the lifetime of the
returned \fB\s-1EVP_PKEY_CTX\s0\fR or any of its duplicates.
.PP
\&\fBEVP_PKEY_CTX_new_id()\fR and \fBEVP_PKEY_CTX_new_from_name()\fR are normally
used when no \fB\s-1EVP_PKEY\s0\fR structure is associated with the operations,
for example during parameter generation or key generation for some
algorithms.
.PP
\&\fBEVP_PKEY_CTX_dup()\fR duplicates the context \fIctx\fR. It is not supported for a
keygen operation.
.PP
\&\fBEVP_PKEY_CTX_free()\fR frees up the context \fIctx\fR.
If \fIctx\fR is \s-1NULL,\s0 nothing is done.
.PP
\&\fBEVP_PKEY_is_a()\fR checks if the key type associated with \fIctx\fR is \fIkeytype\fR.
.SH "NOTES"
.IX Header "NOTES"
.SS "On \fB\s-1EVP_PKEY_CTX\s0\fP"
.IX Subsection "On EVP_PKEY_CTX"
The \fB\s-1EVP_PKEY_CTX\s0\fR structure is an opaque public key algorithm context used
by the OpenSSL high-level public key \s-1API.\s0 Contexts \fB\s-1MUST NOT\s0\fR be shared between
threads: that is it is not permissible to use the same context simultaneously
in two threads.
.SS "On Key Types"
.IX Subsection "On Key Types"
We mention \*(L"key type\*(R" in this manual, which is the same
as \*(L"algorithm\*(R" in most cases, allowing either term to be used
interchangeably. There are algorithms where the \fIkey type\fR and the
\&\fIalgorithm\fR of the operations that use the keys are not the same,
such as \s-1EC\s0 keys being used for \s-1ECDSA\s0 and \s-1ECDH\s0 operations.
.PP
Key types are given in two different manners:
.IP "Legacy \s-1NID\s0 or \s-1EVP_PKEY\s0 type" 4
.IX Item "Legacy NID or EVP_PKEY type"
This is the \fIid\fR used with \fBEVP_PKEY_CTX_new_id()\fR.
.Sp
These are \fB\s-1EVP_PKEY_RSA\s0\fR, \fB\s-1EVP_PKEY_RSA_PSS\s0\fR, \fB\s-1EVP_PKEY_DSA\s0\fR,
\&\fB\s-1EVP_PKEY_DH\s0\fR, \fB\s-1EVP_PKEY_EC\s0\fR, \fB\s-1EVP_PKEY_SM2\s0\fR, \fB\s-1EVP_PKEY_X25519\s0\fR,
\&\fB\s-1EVP_PKEY_X448\s0\fR, and are used by legacy methods.
.IP "Name strings" 4
.IX Item "Name strings"
This is the \fIname\fR used with \fBEVP_PKEY_CTX_new_from_name()\fR.
.Sp
These are names like \*(L"\s-1RSA\*(R", \*(L"DSA\*(R",\s0 and what's available depends on what
providers are currently accessible.
.Sp
The OpenSSL providers offer a set of key types available this way, please
see \s-1\fBOSSL_PROVIDER\-FIPS\s0\fR\|(7) and \fBOSSL_PROVIDER\-default\fR\|(7) and related
documentation for more information.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBEVP_PKEY_CTX_new()\fR, \fBEVP_PKEY_CTX_new_id()\fR and \fBEVP_PKEY_CTX_dup()\fR return either
the newly allocated \fB\s-1EVP_PKEY_CTX\s0\fR structure or \fB\s-1NULL\s0\fR if an error occurred.
.PP
\&\fBEVP_PKEY_CTX_free()\fR does not return a value.
.PP
\&\fBEVP_PKEY_CTX_is_a()\fR returns 1 for true and 0 for false.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBEVP_PKEY_new\fR\|(3)
.SH "HISTORY"
.IX Header "HISTORY"
The \fBEVP_PKEY_CTX_new()\fR, \fBEVP_PKEY_CTX_new_id()\fR, \fBEVP_PKEY_CTX_dup()\fR and
\&\fBEVP_PKEY_CTX_free()\fR functions were added in OpenSSL 1.0.0.
.PP
The \fBEVP_PKEY_CTX_new_from_name()\fR and \fBEVP_PKEY_CTX_new_from_pkey()\fR functions were
added in OpenSSL 3.0.
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2006\-2021 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>.
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