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/**
* \file chacha20.h
*
* \brief This file contains ChaCha20 definitions and functions.
*
* ChaCha20 is a stream cipher that can encrypt and decrypt
* information. ChaCha was created by Daniel Bernstein as a variant of
* its Salsa cipher https://cr.yp.to/chacha/chacha-20080128.pdf
* ChaCha20 is the variant with 20 rounds, that was also standardized
* in RFC 7539.
*
* \author Daniel King <damaki.gh@gmail.com>
*/
/*
* Copyright The Mbed TLS Contributors
* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
*/
#ifndef MBEDTLS_CHACHA20_H
#define MBEDTLS_CHACHA20_H
#include "mbedtls/private_access.h"
#include "mbedtls/build_info.h"
#include <stdint.h>
#include <stddef.h>
/** Invalid input parameter(s). */
#define MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA -0x0051
#ifdef __cplusplus
extern "C" {
#endif
#if !defined(MBEDTLS_CHACHA20_ALT)
typedef struct mbedtls_chacha20_context {
uint32_t MBEDTLS_PRIVATE(state)[16]; /*! The state (before round operations). */
uint8_t MBEDTLS_PRIVATE(keystream8)[64]; /*! Leftover keystream bytes. */
size_t MBEDTLS_PRIVATE(keystream_bytes_used); /*! Number of keystream bytes already used. */
}
mbedtls_chacha20_context;
#else /* MBEDTLS_CHACHA20_ALT */
#include "chacha20_alt.h"
#endif /* MBEDTLS_CHACHA20_ALT */
/**
* \brief This function initializes the specified ChaCha20 context.
*
* It must be the first API called before using
* the context.
*
* It is usually followed by calls to
* \c mbedtls_chacha20_setkey() and
* \c mbedtls_chacha20_starts(), then one or more calls to
* to \c mbedtls_chacha20_update(), and finally to
* \c mbedtls_chacha20_free().
*
* \param ctx The ChaCha20 context to initialize.
* This must not be \c NULL.
*/
void mbedtls_chacha20_init(mbedtls_chacha20_context *ctx);
/**
* \brief This function releases and clears the specified
* ChaCha20 context.
*
* \param ctx The ChaCha20 context to clear. This may be \c NULL,
* in which case this function is a no-op. If it is not
* \c NULL, it must point to an initialized context.
*
*/
void mbedtls_chacha20_free(mbedtls_chacha20_context *ctx);
/**
* \brief This function sets the encryption/decryption key.
*
* \note After using this function, you must also call
* \c mbedtls_chacha20_starts() to set a nonce before you
* start encrypting/decrypting data with
* \c mbedtls_chacha_update().
*
* \param ctx The ChaCha20 context to which the key should be bound.
* It must be initialized.
* \param key The encryption/decryption key. This must be \c 32 Bytes
* in length.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA if ctx or key is NULL.
*/
int mbedtls_chacha20_setkey(mbedtls_chacha20_context *ctx,
const unsigned char key[32]);
/**
* \brief This function sets the nonce and initial counter value.
*
* \note A ChaCha20 context can be re-used with the same key by
* calling this function to change the nonce.
*
* \warning You must never use the same nonce twice with the same key.
* This would void any confidentiality guarantees for the
* messages encrypted with the same nonce and key.
*
* \param ctx The ChaCha20 context to which the nonce should be bound.
* It must be initialized and bound to a key.
* \param nonce The nonce. This must be \c 12 Bytes in size.
* \param counter The initial counter value. This is usually \c 0.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA if ctx or nonce is
* NULL.
*/
int mbedtls_chacha20_starts(mbedtls_chacha20_context *ctx,
const unsigned char nonce[12],
uint32_t counter);
/**
* \brief This function encrypts or decrypts data.
*
* Since ChaCha20 is a stream cipher, the same operation is
* used for encrypting and decrypting data.
*
* \note The \p input and \p output pointers must either be equal or
* point to non-overlapping buffers.
*
* \note \c mbedtls_chacha20_setkey() and
* \c mbedtls_chacha20_starts() must be called at least once
* to setup the context before this function can be called.
*
* \note This function can be called multiple times in a row in
* order to encrypt of decrypt data piecewise with the same
* key and nonce.
*
* \param ctx The ChaCha20 context to use for encryption or decryption.
* It must be initialized and bound to a key and nonce.
* \param size The length of the input data in Bytes.
* \param input The buffer holding the input data.
* This pointer can be \c NULL if `size == 0`.
* \param output The buffer holding the output data.
* This must be able to hold \p size Bytes.
* This pointer can be \c NULL if `size == 0`.
*
* \return \c 0 on success.
* \return A negative error code on failure.
*/
int mbedtls_chacha20_update(mbedtls_chacha20_context *ctx,
size_t size,
const unsigned char *input,
unsigned char *output);
/**
* \brief This function encrypts or decrypts data with ChaCha20 and
* the given key and nonce.
*
* Since ChaCha20 is a stream cipher, the same operation is
* used for encrypting and decrypting data.
*
* \warning You must never use the same (key, nonce) pair more than
* once. This would void any confidentiality guarantees for
* the messages encrypted with the same nonce and key.
*
* \note The \p input and \p output pointers must either be equal or
* point to non-overlapping buffers.
*
* \param key The encryption/decryption key.
* This must be \c 32 Bytes in length.
* \param nonce The nonce. This must be \c 12 Bytes in size.
* \param counter The initial counter value. This is usually \c 0.
* \param size The length of the input data in Bytes.
* \param input The buffer holding the input data.
* This pointer can be \c NULL if `size == 0`.
* \param output The buffer holding the output data.
* This must be able to hold \p size Bytes.
* This pointer can be \c NULL if `size == 0`.
*
* \return \c 0 on success.
* \return A negative error code on failure.
*/
int mbedtls_chacha20_crypt(const unsigned char key[32],
const unsigned char nonce[12],
uint32_t counter,
size_t size,
const unsigned char *input,
unsigned char *output);
#if defined(MBEDTLS_SELF_TEST)
/**
* \brief The ChaCha20 checkup routine.
*
* \return \c 0 on success.
* \return \c 1 on failure.
*/
int mbedtls_chacha20_self_test(int verbose);
#endif /* MBEDTLS_SELF_TEST */
#ifdef __cplusplus
}
#endif
#endif /* MBEDTLS_CHACHA20_H */
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