EVP_chacha20, EVP_chacha20_poly1305 - EVP ChaCha20 stream cipher
 #include <openssl/evp.h>
 const EVP_CIPHER *EVP_chacha20(void);
 const EVP_CIPHER *EVP_chacha20_poly1305(void);
The ChaCha20 stream cipher for EVP.
  - EVP_chacha20()
- The ChaCha20 stream cipher. The key length is 256 bits, the IV is 128 bits
      long. The first 64 bits consists of a counter in little-endian order
      followed by a 64 bit nonce. For example a nonce of:
    0000000000000002 With an initial counter of 42 (2a in hex) would be expressed
        as: 2a000000000000000000000000000002 
- EVP_chacha20_poly1305()
- Authenticated encryption with ChaCha20-Poly1305. Like
      EVP_chacha20(), the key is 256 bits and the IV is 96 bits. This
      supports additional authenticated data (AAD) and produces a 128-bit
      authentication tag. See the "AEAD Interface" in
      EVP_EncryptInit(3) section for more information.
Developers should be aware of the negative performance implications of calling
  these functions multiple times and should consider using
  EVP_CIPHER_fetch(3) with EVP_CIPHER-CHACHA(7) instead. See
  "Performance" in crypto(7) for further information.RFC 7539
    <https://www.rfc-editor.org/rfc/rfc7539.html#section-2.4> uses a 32
    bit counter and a 96 bit nonce for the IV.
These functions return an EVP_CIPHER structure that contains the
  implementation of the symmetric cipher. See EVP_CIPHER_meth_new(3) for
  details of the EVP_CIPHER structure.
evp(7), EVP_EncryptInit(3), EVP_CIPHER_meth_new(3)
Copyright 2017-2023 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>.