linux/lib/crypto/chacha.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * The "hash function" used as the core of the ChaCha stream cipher (RFC7539)
 *
 * Copyright (C) 2015 Martin Willi
 */

#include <linux/bug.h>
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/bitops.h>
#include <linux/string.h>
#include <asm/unaligned.h>
#include <crypto/chacha.h>

static void chacha_permute(u32 *x, int nrounds)
{ … }

/**
 * chacha_block_generic - generate one keystream block and increment block counter
 * @state: input state matrix (16 32-bit words)
 * @stream: output keystream block (64 bytes)
 * @nrounds: number of rounds (20 or 12; 20 is recommended)
 *
 * This is the ChaCha core, a function from 64-byte strings to 64-byte strings.
 * The caller has already converted the endianness of the input.  This function
 * also handles incrementing the block counter in the input matrix.
 */
void chacha_block_generic(u32 *state, u8 *stream, int nrounds)
{ … }
EXPORT_SYMBOL(…);

/**
 * hchacha_block_generic - abbreviated ChaCha core, for XChaCha
 * @state: input state matrix (16 32-bit words)
 * @stream: output (8 32-bit words)
 * @nrounds: number of rounds (20 or 12; 20 is recommended)
 *
 * HChaCha is the ChaCha equivalent of HSalsa and is an intermediate step
 * towards XChaCha (see https://cr.yp.to/snuffle/xsalsa-20081128.pdf).  HChaCha
 * skips the final addition of the initial state, and outputs only certain words
 * of the state.  It should not be used for streaming directly.
 */
void hchacha_block_generic(const u32 *state, u32 *stream, int nrounds)
{ … }
EXPORT_SYMBOL(…);