openssl/doc/man3/EVP_chacha20.pod

=pod

=head1 NAME

EVP_chacha20,
EVP_chacha20_poly1305
- EVP ChaCha20 stream cipher

=head1 SYNOPSIS

 #include <openssl/evp.h>

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

=head1 DESCRIPTION

The ChaCha20 stream cipher for EVP.

=over 4

=item EVP_chacha20()

The ChaCha20 stream cipher. The key length is 256 bits, the IV is 128 bits long.
The first 32 bits consists of a counter in little-endian order followed by a 96
bit nonce. For example a nonce of:

000000000000000000000002

With an initial counter of 42 (2a in hex) would be expressed as:

2a000000000000000000000000000002

=item 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
L<EVP_EncryptInit(3)/AEAD Interface> section for more information.

=back

=head1 RETURN VALUES

These functions return an B<EVP_CIPHER> structure that contains the
implementation of the symmetric cipher. See L<EVP_CIPHER_meth_new(3)> for
details of the B<EVP_CIPHER> structure.

=head1 SEE ALSO

L<evp(7)>,
L<EVP_EncryptInit(3)>,
L<EVP_CIPHER_meth_new(3)>

=head1 COPYRIGHT

Copyright 2017-2019 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (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
L<https://www.openssl.org/source/license.html>.

=cut