EVP_CHACHA20(3SSL) OpenSSL EVP_CHACHA20(3SSL)
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 2017-2025 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>.
3.5.7 2026-06-09 EVP_CHACHA20(3SSL)
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