NAME
life_cycle-cipher - The cipher algorithm life-cycle
DESCRIPTION
All symmetric
ciphers (CIPHERs) go through a number of stages in their
life-cycle:
start
This state represents the CIPHER before it has been allocated. It is the starting state for any life-cycle transitions.
newed
This state represents the CIPHER after it has been allocated.
initialised
These states represent the
CIPHER when it is set up and capable of processing input.
There are three possible initialised states:
initialised using EVP_CipherInit
initialised for decryption using EVP_DecryptInit
initialised for encryption using EVP_EncryptInit
updated
These states represent the CIPHER when it is set up and capable of processing additional input or generating output. The three possible states directly correspond to those for initialised above. The three different streams should not be mixed.
finaled
This state represents the CIPHER when it has generated output.
freed
This state is entered when the CIPHER is freed. It is the terminal state for all life-cycle transitions.
State
Transition Diagram
The usual life-cycle of a CIPHER is illustrated:
+---------------------------+
| |
| start |
| |
+---------------------------+ + - - - - - - - - - - - - - +
| ’ any of the initialised ’
| EVP_CIPHER_CTX_new ’ updated or finaled states
’
v ’ ’
+---------------------------+ + - - - - - - - - - - - - - +
| | |
| newed | | EVP_CIPHER_CTX_reset
| | <----+
+---------------------------+
| | |
+---------+ | +---------+
EVP_DecryptInit | | EVP_CipherInit | EVP_EncryptInit
v v v
+---------------------------+ +---------------------------+
+---------------------------+
| | | | | |
| initialised | | initialised | | initialised |
| for decryption | | | | for encryption |
+---------------------------+ +---------------------------+
+---------------------------+
| | |
| EVP_DecryptUpdate | EVP_CipherUpdate EVP_EncryptUpdate |
| v |
| +---------------------------+ |
| | |--------------------+ |
| | updated | EVP_CipherUpdate | |
| | | <------------------+ |
v +---------------------------+ v
+---------------------------+ |
+---------------------------+
| |---------------------+ | | |
| updated | EVP_DecryptUpdate | | | updated |------+
| for decryption | <-------------------+ | | for
encryption | |
+---------------------------+ |
+---------------------------+ |
| EVP_CipherFinal | | ^ |
+-------+ | +--------+ | |
EVP_DecryptFinal | | | EVP_EncryptFinal
+-------------------+
v v v EVP_EncryptUpdate
+---------------------------+
| |-----------------------------+
| finaled | |
| | <---------------------------+
+---------------------------+ EVP_CIPHER_CTX_get_params
| (AEAD encryption)
| EVP_CIPHER_CTX_free
v
+---------------------------+
| |
| freed |
| |
+---------------------------+
Formal State
Transitions
This section defines all of the legal state transitions.
This is the canonical list.
Function Call ----------------------------------------------
Current State
-----------------------------------------------
start newed initialised updated finaled initialised updated
initialised updated freed
decryption decryption encryption encryption
EVP_CIPHER_CTX_new newed
EVP_CipherInit initialised initialised initialised
initialised initialised initialised initialised initialised
EVP_DecryptInit initialised initialised initialised
initialised initialised initialised initialised initialised
decryption decryption decryption decryption decryption
decryption decryption decryption
EVP_EncryptInit initialised initialised initialised
initialised initialised initialised initialised initialised
encryption encryption encryption encryption encryption
encryption encryption encryption
EVP_CipherUpdate updated updated
EVP_DecryptUpdate updated updated
decryption decryption
EVP_EncryptUpdate updated updated
encryption encryption
EVP_CipherFinal finaled
EVP_DecryptFinal finaled
EVP_EncryptFinal finaled
EVP_CIPHER_CTX_free freed freed freed freed freed freed
freed freed freed
EVP_CIPHER_CTX_reset newed newed newed newed newed newed
newed newed
EVP_CIPHER_CTX_get_params newed initialised updated
initialised updated initialised updated
decryption decryption encryption encryption
EVP_CIPHER_CTX_set_params newed initialised updated
initialised updated initialised updated
decryption decryption encryption encryption
EVP_CIPHER_CTX_gettable_params newed initialised updated
initialised updated initialised updated
decryption decryption encryption encryption
EVP_CIPHER_CTX_settable_params newed initialised updated
initialised updated initialised updated
decryption decryption encryption encryption
NOTES
At some point the EVP layer will begin enforcing the transitions described herein.
SEE ALSO
provider-cipher(7), EVP_EncryptInit(3)
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 <https://www.openssl.org/source/license.html>;.