1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
|
.\" $NetBSD: EVP_SKEY.3,v 1.5 2026/04/08 17:06:44 christos Exp $
.\"
.\" -*- mode: troff; coding: utf-8 -*-
.\" Automatically generated by Pod::Man v6.0.2 (Pod::Simple 3.45)
.\"
.\" 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
..
.\" \*(C` and \*(C' are quotes in nroff, nothing in troff, for use with C<>.
.ie n \{\
. ds C` ""
. ds C' ""
'br\}
.el\{\
. 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
.\"
.\" Required to disable full justification in groff 1.23.0.
.if n .ds AD l
.\" ========================================================================
.\"
.IX Title "EVP_SKEY 3"
.TH EVP_SKEY 3 2026-04-07 3.5.6 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_SKEY, EVP_SKEY_generate,
EVP_SKEY_import, EVP_SKEY_import_raw_key, EVP_SKEY_up_ref,
EVP_SKEY_export, EVP_SKEY_get0_raw_key, EVP_SKEY_get0_key_id,
EVP_SKEY_get0_skeymgmt_name, EVP_SKEY_get0_provider_name,
EVP_SKEY_free, EVP_SKEY_is_a, EVP_SKEY_to_provider
\&\- opaque symmetric key allocation and handling functions
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/evp.h>
\&
\& typedef evp_skey_st EVP_SKEY;
\&
\& EVP_SKEY *EVP_SKEY_generate(OSSL_LIB_CTX *libctx, const char *skeymgmtname,
\& const char *propquery, const OSSL_PARAM *params);
\& EVP_SKEY *EVP_SKEY_import(OSSL_LIB_CTX *libctx, const char *skeymgmtname,
\& const char *propquery,
\& int selection, const OSSL_PARAM *params);
\& EVP_SKEY *EVP_SKEY_import_raw_key(OSSL_LIB_CTX *libctx, const char *skeymgmtname,
\& unsigned char *key, size_t len,
\& const char *propquery);
\& int EVP_SKEY_export(const EVP_SKEY *skey, int selection,
\& OSSL_CALLBACK *export_cb, void *export_cbarg);
\& int EVP_SKEY_get0_raw_key(const EVP_SKEY *skey, const unsigned char **key,
\& size_t *len);
\& const char *EVP_SKEY_get0_key_id(const EVP_SKEY *skey);
\&
\& const char *EVP_SKEY_get0_skeymgmt_name(const EVP_SKEY *skey);
\& const char *EVP_SKEY_get0_provider_name(const EVP_SKEY *skey);
\&
\& int EVP_SKEY_up_ref(EVP_SKEY *key);
\& void EVP_SKEY_free(EVP_SKEY *key);
\& int EVP_SKEY_is_a(const EVP_SKEY *skey, const char *name);
\& EVP_SKEY *EVP_SKEY_to_provider(EVP_SKEY *skey, OSSL_LIB_CTX *libctx,
\& OSSL_PROVIDER *prov, const char *propquery);
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
\&\fBEVP_SKEY\fR is a generic structure to hold symmetric keys as opaque objects.
The keys themselves are often referred to as the "internal key", and are handled by
providers using \fBEVP_SKEYMGMT\fR\|(3).
.PP
Conceptually, an \fBEVP_SKEY\fR internal key may hold a symmetric key, and along
with those, key parameters if the key type requires them.
.PP
The \fBEVP_SKEY_generate()\fR functions creates a new \fBEVP_SKEY\fR object and
initializes it according to the \fBparams\fR argument.
.PP
The \fBEVP_SKEY_import()\fR function allocates an empty \fBEVP_SKEY\fR structure
which is used by OpenSSL to store symmetric keys, assigns the
\&\fBEVP_SKEYMGMT\fR object associated with the key, and initializes the object from
the \fBparams\fR argument.
.PP
The \fBEVP_SKEY_import_raw_key()\fR function is a helper that creates an \fBEVP_SKEY\fR
object containing the raw byte representation of the symmetric keys from the
buffer \fIkey\fR having length \fIlen\fR. The \fIskeymgmtname\fR defines the name of the
target \fBEVP_SKEYMGMT\fR for the newly created key.
.PP
The \fBEVP_SKEY_export()\fR function extracts values from a key \fIskey\fR using the
\&\fIselection\fR. \fIselection\fR is described below. It uses a callback \fIexport_cb\fR
that gets passed the value of \fIexport_cbarg\fR. See \fBopenssl\-core.h\fR\|(7) for
more information about the callback. Note that the \fBOSSL_PARAM\fR\|(3) array that
is passed to the callback is not persistent after the callback returns.
.PP
The \fBEVP_SKEY_get0_raw_key()\fR returns a pointer to a raw key bytes to the passed
address and sets the key len. The returned address is managed by the internal
key management and shouldn\*(Aqt be freed explicitly. The operation can fail when
the underlying key management doesn\*(Aqt support export of the secret key.
.PP
The \fBEVP_SKEY_get0_key_id()\fR returns a NUL\-terminated string providing some
human\-readable identifier of the key if provided by the underlying key
management. The pointer becomes invalid after freeing the EVP_SKEY object.
.PP
The \fBEVP_SKEY_get0_skeymgmt_name()\fR and \fBEVP_SKEY_get0_provider_name()\fR return the
names of the associated EVP_SKEYMGMT object and its provider correspondingly.
.PP
\&\fBEVP_SKEY_up_ref()\fR increments the reference count of \fIkey\fR.
.PP
\&\fBEVP_SKEY_free()\fR decrements the reference count of \fIkey\fR and, if the reference
count is zero, frees it. If \fIkey\fR is NULL, nothing is done.
.PP
\&\fBEVP_SKEY_is_a()\fR checks if the key type of \fIskey\fR is \fIname\fR.
.PP
\&\fBEVP_SKEY_to_provider()\fR simplifies the task of importing a \fIskey\fR into a
different provider identified by \fIprov\fR. If \fIprov\fR is NULL, the default
provider for the key type identified via \fIskey\fR is used.
.SS Selections
.IX Subsection "Selections"
The following constants can be used for \fIselection\fR:
.IP \fBOSSL_SKEYMGMT_SELECT_SECRET_KEY\fR 4
.IX Item "OSSL_SKEYMGMT_SELECT_SECRET_KEY"
Only the raw key representation will be selected.
.IP \fBOSSL_SKEYMGMT_SELECT_PARAMETERS\fR 4
.IX Item "OSSL_SKEYMGMT_SELECT_PARAMETERS"
Only the key parameters will be selected. This includes optional key
parameters.
.IP \fBOSSL_SKEYMGMT_SELECT_ALL\fR 4
.IX Item "OSSL_SKEYMGMT_SELECT_ALL"
All parameters will be selected.
.SH NOTES
.IX Header "NOTES"
The \fBEVP_SKEY\fR structure is used by various OpenSSL functions which require a
general symmetric key without reference to any particular algorithm.
.PP
The \fBEVP_SKEY_to_provider()\fR function will fail and return NULL if the origin
key \fIskey\fR cannot be exported from its provider.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBEVP_SKEY_generate()\fR, \fBEVP_SKEY_import()\fR and \fBEVP_SKEY_import_raw_key()\fR return
either the newly allocated \fBEVP_SKEY\fR structure or NULL if an error occurred.
.PP
\&\fBEVP_SKEY_get0_key_id()\fR returns either a valid pointer or NULL.
.PP
\&\fBEVP_SKEY_up_ref()\fR returns 1 for success and 0 on failure.
.PP
\&\fBEVP_SKEY_export()\fR and \fBEVP_SKEY_get0_raw_key()\fR return 1 for success and 0 on failure.
.PP
\&\fBEVP_SKEY_get0_skeymgmt_name()\fR and \fBEVP_SKEY_get0_provider_name()\fR return the
names of the associated EVP_SKEYMGMT object and its provider correspondingly.
.PP
\&\fBEVP_SKEY_is_a()\fR returns 1 if \fIskey\fR has the key type \fIname\fR,
otherwise 0.
.PP
\&\fBEVP_SKEY_to_provider()\fR returns a new \fBEVP_SKEY\fR suitable for operations with
the \fIprov\fR provider or NULL in case of failure.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBEVP_SKEYMGMT\fR\|(3), \fBprovider\fR\|(7), \fBOSSL_PARAM\fR\|(3)
.SH HISTORY
.IX Header "HISTORY"
The \fBEVP_SKEY\fR API and functions \fBEVP_SKEY_export()\fR,
\&\fBEVP_SKEY_free()\fR, \fBEVP_SKEY_get0_raw_key()\fR, \fBEVP_SKEY_import()\fR,
\&\fBEVP_SKEY_import_raw_key()\fR, \fBEVP_SKEY_up_ref()\fR, \fBEVP_SKEY_generate()\fR,
\&\fBEVP_SKEY_get0_key_id()\fR, \fBEVP_SKEY_get0_provider_name()\fR,
\&\fBEVP_SKEY_get0_skeymgmt_name()\fR, \fBEVP_SKEY_is_a()\fR, \fBEVP_SKEY_to_provider()\fR
were introduced in OpenSSL 3.5.
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright 2025\-2026 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the Apache License 2.0 (the "License"). You may not use
this file except in compliance with the License. You can obtain a copy
in the file LICENSE in the source distribution or at
<https://www.openssl.org/source/license.html>.
|
