life_cycle-cipher - The cipher algorithm life-cycle All symmetric ciphers (CIPHERs) go through a number of stages in their life-cycle: This state represents the CIPHER before it has been allocated. It is the starting state for any life-cycle transitions. This state represents the CIPHER after it has been allocated. These states represent the CIPHER when it is set up and capable of processing input. There are three possible initialised states: 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. This state represents the CIPHER when it has generated output. 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 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>.