LIFE_CYCLE-CIPHER(7) | OpenSSL | LIFE_CYCLE-CIPHER(7)

# 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>.

2025-02-11 | 3.0.16