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.\" ========================================================================
.\"
.IX Title "LIFE_CYCLE-PKEY 7ossl"
.TH LIFE_CYCLE-PKEY 7ossl "2026-01-27" "3.5.5" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.nh
.SH "NAME"
life_cycle\-pkey \- The PKEY algorithm life\-cycle
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
All public keys (PKEYs) go through a number of stages in their life-cycle:
.IP "start" 4
.IX Item "start"
This state represents the \s-1PKEY\s0 before it has been allocated.  It is the
starting state for any life-cycle transitions.
.IP "newed" 4
.IX Item "newed"
This state represents the \s-1PKEY\s0 after it has been allocated.
.IP "decapsulate" 4
.IX Item "decapsulate"
This state represents the \s-1PKEY\s0 when it is ready to perform a private key decapsulation
operation.
.IP "decrypt" 4
.IX Item "decrypt"
This state represents the \s-1PKEY\s0 when it is ready to decrypt some ciphertext.
.IP "derive" 4
.IX Item "derive"
This state represents the \s-1PKEY\s0 when it is ready to derive a shared secret.
.IP "digest sign" 4
.IX Item "digest sign"
This state represents the \s-1PKEY\s0 when it is ready to perform a private key signature
operation.
.IP "encapsulate" 4
.IX Item "encapsulate"
This state represents the \s-1PKEY\s0 when it is ready to perform a public key encapsulation
operation.
.IP "encrypt" 4
.IX Item "encrypt"
This state represents the \s-1PKEY\s0 when it is ready to encrypt some plaintext.
.IP "key generation" 4
.IX Item "key generation"
This state represents the \s-1PKEY\s0 when it is ready to generate a new public/private key.
.IP "parameter generation" 4
.IX Item "parameter generation"
This state represents the \s-1PKEY\s0 when it is ready to generate key parameters.
.IP "verify" 4
.IX Item "verify"
This state represents the \s-1PKEY\s0 when it is ready to verify a public key signature.
.IP "verify recover" 4
.IX Item "verify recover"
This state represents the \s-1PKEY\s0 when it is ready to recover a public key signature data.
.IP "freed" 4
.IX Item "freed"
This state is entered when the \s-1PKEY\s0 is freed.  It is the terminal state
for all life-cycle transitions.
.SS "State Transition Diagram"
.IX Subsection "State Transition Diagram"
The usual life-cycle of a \s-1PKEY\s0 object is illustrated:
                                                   +-------------+
                                                   |             |
                                                   |    start    |
                                                   |             |
                   EVP_PKEY_derive                 +-------------+
 +-------------+   EVP_PKEY_derive_set_peer               |                                          +-------------+
 |             |----------------------------+             |             +----------------------------|             |
 |   derive    |                            |             |             |  EVP_PKEY_verify           |   verify    |
 |             |<---------------------------+             |             +--------------------------->|             |
 +-------------+                                          |                                          +-------------+
             ^                                            |                                            ^
             |   EVP_PKEY_derive_init                     |             EVP_PKEY_verify_init           |
             +---------------------------------------+    |    +---------------------------------------+
                                                     |    |    |
 +-------------+                                     |    |    |                                     +-------------+
 |             |----------------------------+        |    |    |        +----------------------------|             |
 | digest sign |   EVP_PKEY_sign            |        |    |    |        |  EVP_PKEY_verify_recover   |   verify    |
 |             |<---------------------------+        |    |    |        +--------------------------->|   recover   |
 +-------------+                                     |    |    |                                     +-------------+
             ^                                       |    |    |                                       ^
             |     EVP_PKEY_sign_init                |    |    |        EVP_PKEY_verify_recover_init   |
             +---------------------------------+     |    |    |     +---------------------------------+
                                               |     |    |    |     |
 +-------------+                               |     |    |    |     |                               +-------------+
 |             |----------------------------+  |     |    |    |     |  +----------------------------|             |
 | decapsulate |   EVP_PKEY_decapsulate     |  |     |    |    |     |  |  EVP_PKEY_decrypt          |   decrypt   |
 |             |<---------------------------+  |     |    v    |     |  +--------------------------->|             |
 +-------------+                               |   +-------------+   |                               +-------------+
             ^                                 +---|             |---+                                 ^
             |     EVP_PKEY_decapsulate_init       |             |      EVP_PKEY_decrypt_init          |
             +-------------------------------------|    newed    |-------------------------------------+
                                                   |             |
                                               +---|             |---+
 +-------------+                               |   +-------------+   |                               +-------------+
 |             |----------------------------+  |     |         |     |  +----------------------------|             |
 | encapsulate |   EVP_PKEY_encapsulate     |  |     |         |     |  |  EVP_PKEY_encrypt          |   encrypt   |
 |             |<---------------------------+  |     |         |     |  +--------------------------->|             |
 +-------------+                               |     |         |     |                               +-------------+
             ^                                 |     |         |     |                                 ^
             |     EVP_PKEY_encapsulate_init   |     |         |     |  EVP_PKEY_encrypt_init          |
             +---------------------------------+     |         |     +---------------------------------+
                                                     |         |
             +---------------------------------------+         +---------------------------------------+
             |     EVP_PKEY_paramgen_init                               EVP_PKEY_keygen_init           |
             v                                                                                         v
 +-------------+                                                                                     +-------------+
 |             |----------------------------+                           +----------------------------|             |
 |  parameter  |                            |                           |                            |     key     |
 |  generation |<---------------------------+                           +--------------------------->|  generation |
 +-------------+   EVP_PKEY_paramgen                                       EVP_PKEY_keygen           +-------------+
                   EVP_PKEY_gen                                            EVP_PKEY_gen


                                    + - - - - - +                    +-----------+
                                    '           ' EVP_PKEY_CTX_free  |           |
                                    ' any state '------------------->|   freed   |
                                    '           '                    |           |
                                    + - - - - - +                    +-----------+
.SS "Formal State Transitions"
.IX Subsection "Formal State Transitions"
This section defines all of the legal state transitions.
This is the canonical list.
 Function Call                 ---------------------------------------------------------------------- Current State ----------------------------------------------------------------------
                               start    newed       digest       verify       verify       encrypt      decrypt      derive      encapsulate  decapsulate  parameter       key       freed
                                                     sign                     recover                                                                      generation   generation
 EVP_PKEY_CTX_new              newed
 EVP_PKEY_CTX_new_id           newed
 EVP_PKEY_CTX_new_from_name    newed
 EVP_PKEY_CTX_new_from_pkey    newed
 EVP_PKEY_sign_init                    digest       digest       digest       digest       digest       digest       digest       digest       digest       digest       digest
                                        sign         sign         sign         sign         sign         sign         sign         sign         sign         sign         sign
 EVP_PKEY_sign                                      digest
                                                     sign
 EVP_PKEY_verify_init                  verify       verify       verify       verify       verify       verify       verify       verify       verify       verify       verify
 EVP_PKEY_verify                                                 verify
 EVP_PKEY_verify_recover_init          verify       verify       verify       verify       verify       verify       verify       verify       verify       verify       verify
                                       recover      recover      recover      recover      recover      recover      recover      recover      recover      recover      recover
 EVP_PKEY_verify_recover                                                      verify
                                                                              recover
 EVP_PKEY_encrypt_init                 encrypt      encrypt      encrypt      encrypt      encrypt      encrypt      encrypt      encrypt      encrypt      encrypt      encrypt
 EVP_PKEY_encrypt                                                                          encrypt
 EVP_PKEY_decrypt_init                 decrypt      decrypt      decrypt      decrypt      decrypt      decrypt      decrypt      decrypt      decrypt      decrypt      decrypt
 EVP_PKEY_decrypt                                                                                       decrypt
 EVP_PKEY_derive_init                  derive       derive       derive       derive       derive       derive       derive       derive       derive       derive       derive
 EVP_PKEY_derive_set_peer                                                                                            derive
 EVP_PKEY_derive                                                                                                     derive
 EVP_PKEY_encapsulate_init            encapsulate  encapsulate  encapsulate  encapsulate  encapsulate  encapsulate  encapsulate  encapsulate  encapsulate  encapsulate  encapsulate
 EVP_PKEY_encapsulate                                                                                                            encapsulate
 EVP_PKEY_decapsulate_init            decapsulate  decapsulate  decapsulate  decapsulate  decapsulate  decapsulate  decapsulate  decapsulate  decapsulate  decapsulate  decapsulate
 EVP_PKEY_decapsulate                                                                                                                         decapsulate
 EVP_PKEY_paramgen_init               parameter    parameter    parameter    parameter    parameter    parameter    parameter    parameter    parameter    parameter    parameter
                                      generation   generation   generation   generation   generation   generation   generation   generation   generation   generation   generation
 EVP_PKEY_paramgen                                                                                                                                         parameter
                                                                                                                                                           generation
 EVP_PKEY_keygen_init                    key          key          key          key          key          key          key          key          key          key          key
                                      generation   generation   generation   generation   generation   generation   generation   generation   generation   generation   generation
 EVP_PKEY_keygen                                                                                                                                                           key
                                                                                                                                                                        generation
 EVP_PKEY_gen                                                                                                                                              parameter       key
                                                                                                                                                           generation   generation
 EVP_PKEY_CTX_get_params                newed       digest       verify       verify       encrypt      decrypt      derive      encapsulate  decapsulate  parameter       key
                                                     sign                     recover                                                                      generation   generation
 EVP_PKEY_CTX_set_params                newed       digest       verify       verify       encrypt      decrypt      derive      encapsulate  decapsulate  parameter       key
                                                     sign                     recover                                                                      generation   generation
 EVP_PKEY_CTX_gettable_params           newed       digest       verify       verify       encrypt      decrypt      derive      encapsulate  decapsulate  parameter       key
                                                     sign                     recover                                                                      generation   generation
 EVP_PKEY_CTX_settable_params           newed       digest       verify       verify       encrypt      decrypt      derive      encapsulate  decapsulate  parameter       key
                                                     sign                     recover                                                                      generation   generation
 EVP_PKEY_CTX_free             freed    freed        freed        freed        freed        freed        freed        freed        freed        freed        freed        freed
.SH "NOTES"
.IX Header "NOTES"
At some point the \s-1EVP\s0 layer will begin enforcing the transitions described
herein.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBEVP_PKEY_new\fR\|(3),
\&\fBEVP_PKEY_decapsulate\fR\|(3), \fBEVP_PKEY_decrypt\fR\|(3), \fBEVP_PKEY_encapsulate\fR\|(3),
\&\fBEVP_PKEY_encrypt\fR\|(3), \fBEVP_PKEY_derive\fR\|(3), \fBEVP_PKEY_keygen\fR\|(3),
\&\fBEVP_PKEY_sign\fR\|(3), \fBEVP_PKEY_verify\fR\|(3), \fBEVP_PKEY_verify_recover\fR\|(3)
.SH "HISTORY"
.IX Header "HISTORY"
The provider \s-1PKEY\s0 interface was introduced in OpenSSL 3.0.
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2021\-2022 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>.
