EVP_CHACHA20(3ossl)

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 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 2017-2025 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>.