133 lines
4.4 KiB
Plaintext
133 lines
4.4 KiB
Plaintext
|
.\" This file is dual-licensed. Choose whichever you want.
|
||
|
|
.\"
|
||
|
|
.\" The first licence is a regular 2-clause BSD licence. The second licence
|
||
|
|
.\" is the CC-0 from Creative Commons. It is intended to release Monocypher
|
||
|
|
.\" to the public domain. The BSD licence serves as a fallback option.
|
||
|
|
.\"
|
||
|
|
.\" SPDX-License-Identifier: BSD-2-Clause OR CC0-1.0
|
||
|
|
.\"
|
||
|
|
.\" ----------------------------------------------------------------------------
|
||
|
|
.\"
|
||
|
|
.\" Copyright (c) 2019-2020 Fabio Scotoni
|
||
|
|
.\" All rights reserved.
|
||
|
|
.\"
|
||
|
|
.\"
|
||
|
|
.\" Redistribution and use in source and binary forms, with or without
|
||
|
|
.\" modification, are permitted provided that the following conditions are
|
||
|
|
.\" met:
|
||
|
|
.\"
|
||
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
||
|
|
.\" notice, this list of conditions and the following disclaimer.
|
||
|
|
.\"
|
||
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
||
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
||
|
|
.\" documentation and/or other materials provided with the
|
||
|
|
.\" distribution.
|
||
|
|
.\"
|
||
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
|
||
|
|
.\" "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
|
||
|
|
.\" LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
|
||
|
|
.\" A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
|
||
|
|
.\" HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
|
||
|
|
.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
|
||
|
|
.\" LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
|
||
|
|
.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
|
||
|
|
.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
|
||
|
|
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
|
||
|
|
.\" OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
||
|
|
.\"
|
||
|
|
.\" ----------------------------------------------------------------------------
|
||
|
|
.\"
|
||
|
|
.\" Written in 2019-2020 by Fabio Scotoni
|
||
|
|
.\"
|
||
|
|
.\" To the extent possible under law, the author(s) have dedicated all copyright
|
||
|
|
.\" and related neighboring rights to this software to the public domain
|
||
|
|
.\" worldwide. This software is distributed without any warranty.
|
||
|
|
.\"
|
||
|
|
.\" You should have received a copy of the CC0 Public Domain Dedication along
|
||
|
|
.\" with this software. If not, see
|
||
|
|
.\" <https://creativecommons.org/publicdomain/zero/1.0/>
|
||
|
|
.\"
|
||
|
|
.Dd March 31, 2020
|
||
|
|
.Dt CRYPTO_IETF_CHACHA20 3MONOCYPHER
|
||
|
|
.Os
|
||
|
|
.Sh NAME
|
||
|
|
.Nm crypto_ietf_chacha20 ,
|
||
|
|
.Nm crypto_ietf_chacha20_ctr
|
||
|
|
.Nd IETF Chacha20 encryption functions
|
||
|
|
.Sh SYNOPSIS
|
||
|
|
.In monocypher.h
|
||
|
|
.Ft void
|
||
|
|
.Fo crypto_ietf_chacha20
|
||
|
|
.Fa "uint8_t *cipher_text"
|
||
|
|
.Fa "const uint8_t *plain_text"
|
||
|
|
.Fa "size_t text_size"
|
||
|
|
.Fa "const uint8_t key[32]"
|
||
|
|
.Fa "const uint8_t nonce[12]"
|
||
|
|
.Fc
|
||
|
|
.Ft void
|
||
|
|
.Fo crypto_ietf_chacha20_ctr
|
||
|
|
.Fa "uint8_t *cipher_text"
|
||
|
|
.Fa "const uint8_t *plain_text"
|
||
|
|
.Fa "size_t text_size"
|
||
|
|
.Fa "const uint8_t key[32]"
|
||
|
|
.Fa "const uint8_t nonce[12]"
|
||
|
|
.Fa "const uint32_t ctr"
|
||
|
|
.Fc
|
||
|
|
.Sh DESCRIPTION
|
||
|
|
These functions provide an interface for the Chacha20 encryption
|
||
|
|
primitive as specified by the IETF in RFC 8439.
|
||
|
|
They are provided strictly for compatibility with existing systems
|
||
|
|
or strict standards compliance.
|
||
|
|
New programs are strongly encouraged to use
|
||
|
|
.Xr crypto_xchacha20 3monocypher
|
||
|
|
instead.
|
||
|
|
.Pp
|
||
|
|
Chacha20 is a low-level primitive.
|
||
|
|
Consider using authenticated encryption, implemented by
|
||
|
|
.Xr crypto_lock 3monocypher .
|
||
|
|
.Pp
|
||
|
|
The
|
||
|
|
.Fn crypto_ietf_chacha20
|
||
|
|
and
|
||
|
|
.Fn crypto_ietf_chacha20_ctr
|
||
|
|
functions behave the same as
|
||
|
|
.Xr crypto_chacha20
|
||
|
|
and
|
||
|
|
.Xr crypto_chacha20_ctr ,
|
||
|
|
respectively,
|
||
|
|
but use differently-sized nonce and counter values.
|
||
|
|
The nonce encompasses 12 bytes and the counter is correspondingly
|
||
|
|
reduced to 4 bytes.
|
||
|
|
The short counter limits a single pair of key and nonce to 256 GiB of
|
||
|
|
data.
|
||
|
|
A nonce of 12 bytes is
|
||
|
|
.Em just barely too short
|
||
|
|
to be safely chosen at random;
|
||
|
|
use a message counter instead.
|
||
|
|
RFC 8439 also permits linear feedback shift registers to generate
|
||
|
|
nonces.
|
||
|
|
.Sh RETURN VALUES
|
||
|
|
.Fn crypto_ietf_chacha20
|
||
|
|
returns nothing.
|
||
|
|
.Fn crypto_ietf_chacha20_ctr
|
||
|
|
functions return the next
|
||
|
|
.Fa ctr
|
||
|
|
to use with the same key and nonce values;
|
||
|
|
this is always
|
||
|
|
.Fa text_size
|
||
|
|
divided by 64;
|
||
|
|
plus one if there was a remainder.
|
||
|
|
.Sh SEE ALSO
|
||
|
|
.Xr crypto_chacha20 3monocypher ,
|
||
|
|
.Xr crypto_lock 3monocypher ,
|
||
|
|
.Xr crypto_wipe 3monocypher ,
|
||
|
|
.Xr intro 3monocypher
|
||
|
|
.Sh STANDARDS
|
||
|
|
These functions implement Chacha20 as described in RFC 8439.
|
||
|
|
.Sh HISTORY
|
||
|
|
.Fn crypto_ietf_chacha20
|
||
|
|
and
|
||
|
|
.Fn crypto_ietf_chacha20_ctr
|
||
|
|
were added in Monocypher 3.0.0.
|