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>.