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✏️ Editing: EVP_chacha20.3

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.\" ========================================================================
.\"
.IX Title "EVP_CHACHA20 3"
.TH EVP_CHACHA20 3 "2023-09-11" "1.1.1w" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
EVP_chacha20, EVP_chacha20_poly1305 \&\- EVP ChaCha20 stream cipher
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/evp.h>
\&
\& const EVP_CIPHER *EVP_chacha20(void)
\& const EVP_CIPHER *EVP_chacha20_poly1305(void)
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The ChaCha20 stream cipher for \s-1EVP.\s0
.IP "\fBEVP_chacha20()\fR" 4
.IX Item "EVP_chacha20()"
The ChaCha20 stream cipher. The key length is 256 bits, the \s-1IV\s0 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:
.Sp
000000000000000000000002
.Sp
With an initial counter of 42 (2a in hex) would be expressed as:
.Sp
2a000000000000000000000000000002
.IP "\fBEVP_chacha20_poly1305()\fR" 4
.IX Item "EVP_chacha20_poly1305()"
Authenticated encryption with ChaCha20\-Poly1305. Like \fBEVP_chacha20()\fR, the key
is 256 bits and the \s-1IV\s0 is 96 bits. This supports additional authenticated data
(\s-1AAD\s0) and produces a 128\-bit authentication tag. See the
\&\*(L"\s-1AEAD\s0 Interface\*(R" in \fBEVP_EncryptInit\fR\|(3) section for more information.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
These functions return an \fB\s-1EVP_CIPHER\s0\fR structure that contains the
implementation of the symmetric cipher. See \fBEVP_CIPHER_meth_new\fR\|(3) for
details of the \fB\s-1EVP_CIPHER\s0\fR structure.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBevp\fR\|(7),
\&\fBEVP_EncryptInit\fR\|(3),
\&\fBEVP_CIPHER_meth_new\fR\|(3)
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2017\-2019 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the OpenSSL license (the \*(L"License\*(R").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file \s-1LICENSE\s0 in the source distribution or at
<https://www.openssl.org/source/license.html>.

MR SKB