NAME

       EVP_chacha20, EVP_chacha20_poly1305 - EVP ChaCha20 stream cipher

SYNOPSIS

        #include <openssl/evp.h>

        const EVP_CIPHER *EVP_chacha20(void);
        const EVP_CIPHER *EVP_chacha20_poly1305(void);

DESCRIPTION

       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.

NOTES

       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.

RETURN VALUES

       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.

SEE ALSO

       evp(7), EVP_EncryptInit(3), EVP_CIPHER_meth_new(3)

COPYRIGHT

       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>.

3.0.13                                             2025-02-05                                 EVP_CHACHA20(3SSL)