Updated: 2022/Sep/29

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EVP_chacha20(3)                     OpenSSL                    EVP_chacha20(3)



NAME
       EVP_chacha20, EVP_chacha20_poly1305 - EVP ChaCha20 stream cipher

LIBRARY
       libcrypto, -lcrypto

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>.



3.0.12                            2023-10-25                   EVP_chacha20(3)