life_cycle-cipher - The cipher algorithm life-cycle
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.
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 |
 | |
 +---------------------------+
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
At some point the EVP layer will begin enforcing the transitions described
  herein.
provider-cipher(7), EVP_EncryptInit(3)
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>.