=pod
=head1 NAME
life_cycle-kdf - The KDF algorithm life-cycle
=head1 DESCRIPTION
All key derivation functions (KDFs) and pseudo random functions (PRFs)
go through a number of stages in their life-cycle:
=over 4
=item start
This state represents the KDF/PRF before it has been allocated. It is the
starting state for any life-cycle transitions.
=item newed
This state represents the KDF/PRF after it has been allocated.
=item deriving
This state represents the KDF/PRF when it is set up and capable of generating
output.
=item freed
This state is entered when the KDF/PRF is freed. It is the terminal state
for all life-cycle transitions.
=back
=head2 State Transition Diagram
The usual life-cycle of a KDF/PRF is illustrated:
=begin man
+-------------------+
| start |
+-------------------+
|
| EVP_KDF_CTX_new
v
+-------------------+
| newed | <+
+-------------------+ |
| |
| EVP_KDF_derive |
v | EVP_KDF_CTX_reset
EVP_KDF_derive +-------------------+ |
+ - - - - - - - - | | |
' | deriving | |
+ - - - - - - - -> | | -+
+-------------------+
|
| EVP_KDF_CTX_free
v
+-------------------+
| freed |
+-------------------+
=end man
=for html 
=head2 Formal State Transitions
This section defines all of the legal state transitions.
This is the canonical list.
=begin man
Function Call ------------- Current State -------------
start newed deriving freed
EVP_KDF_CTX_new newed
EVP_KDF_derive deriving deriving
EVP_KDF_CTX_free freed freed freed
EVP_KDF_CTX_reset newed newed
EVP_KDF_CTX_get_params newed deriving
EVP_KDF_CTX_set_params newed deriving
EVP_KDF_CTX_gettable_params newed deriving
EVP_KDF_CTX_settable_params newed deriving
=end man
=begin html
| Function Call |
Current State |
|---|
|
start |
newed |
deriving |
freed |
|---|
| EVP_KDF_CTX_new |
newed |
|
|
|
|---|
| EVP_KDF_derive |
|
newed |
deriving |
|
|---|
| EVP_KDF_CTX_free |
|
newed |
deriving |
|
|---|
| EVP_KDF_CTX_reset |
freed |
freed |
freed |
|
|---|
| EVP_KDF_CTX_get_params |
|
newed |
deriving |
|
|---|
| EVP_KDF_CTX_set_params |
|
newed |
deriving |
|
|---|
| EVP_KDF_CTX_gettable_params |
|
newed |
deriving |
|
|---|
| EVP_KDF_CTX_settable_params |
|
newed |
deriving |
|
|---|
=end html
=head1 NOTES
At some point the EVP layer will begin enforcing the transitions described
herein.
=head1 SEE ALSO
L, L.
=head1 HISTORY
The provider KDF interface was introduced in OpenSSL 3.0.
=head1 COPYRIGHT
Copyright 2021 The OpenSSL Project Authors. All Rights Reserved.
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
L.
=cut