chacha20.h File Reference

This file contains ChaCha20 definitions and functions. More...

#include "config.h"
#include <stdint.h>
#include <stddef.h>

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Classes
struct	mbedtls_chacha20_context

Macros
#define	MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA   -0x0051
#define	MBEDTLS_ERR_CHACHA20_FEATURE_UNAVAILABLE   -0x0053
#define	MBEDTLS_ERR_CHACHA20_HW_ACCEL_FAILED   -0x0055

Typedefs
typedef struct mbedtls_chacha20_context	mbedtls_chacha20_context

Functions
void	mbedtls_chacha20_init (mbedtls_chacha20_context *ctx)
	This function initializes the specified ChaCha20 context. More...
void	mbedtls_chacha20_free (mbedtls_chacha20_context *ctx)
	This function releases and clears the specified ChaCha20 context. More...
int	mbedtls_chacha20_setkey (mbedtls_chacha20_context *ctx, const unsigned char key[32])
	This function sets the encryption/decryption key. More...
int	mbedtls_chacha20_starts (mbedtls_chacha20_context *ctx, const unsigned char nonce[12], uint32_t counter)
	This function sets the nonce and initial counter value. More...
int	mbedtls_chacha20_update (mbedtls_chacha20_context *ctx, size_t size, const unsigned char *input, unsigned char *output)
	This function encrypts or decrypts data. More...
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)
	This function encrypts or decrypts data with ChaCha20 and the given key and nonce. More...

Detailed Description

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 damak.nosp@m.i.gh.nosp@m.@gmai.nosp@m.l.co.nosp@m.m

Macro Definition Documentation

MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA

#define MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA   -0x0051

Invalid input parameter(s).

MBEDTLS_ERR_CHACHA20_FEATURE_UNAVAILABLE

#define MBEDTLS_ERR_CHACHA20_FEATURE_UNAVAILABLE   -0x0053

Feature not available. For example, s part of the API is not implemented.

MBEDTLS_ERR_CHACHA20_HW_ACCEL_FAILED

#define MBEDTLS_ERR_CHACHA20_HW_ACCEL_FAILED   -0x0055

Chacha20 hardware accelerator failed.

Typedef Documentation

mbedtls_chacha20_context

typedef struct mbedtls_chacha20_context mbedtls_chacha20_context

Function Documentation

mbedtls_chacha20_crypt()

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
	)

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 input and output pointers must either be equal or point to non-overlapping buffers.

Parameters

key	The encryption/decryption key. This must be 32 Bytes in length.
nonce	The nonce. This must be 12 Bytes in size.
counter	The initial counter value. This is usually 0.
size	The length of the input data in Bytes.
input	The buffer holding the input data. This pointer can be NULL if size == 0.
output	The buffer holding the output data. This must be able to hold size Bytes. This pointer can be NULL if size == 0.

Returns

0 on success.

A negative error code on failure.

mbedtls_chacha20_free()

void mbedtls_chacha20_free

(

mbedtls_chacha20_context *

ctx

)

This function releases and clears the specified ChaCha20 context.

Parameters

ctx	The ChaCha20 context to clear. This may be NULL, in which case this function is a no-op. If it is not NULL, it must point to an initialized context.

mbedtls_chacha20_init()

void mbedtls_chacha20_init

(

mbedtls_chacha20_context *

ctx

)

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().

Parameters

ctx	The ChaCha20 context to initialize. This must not be NULL.

mbedtls_chacha20_setkey()

int mbedtls_chacha20_setkey	(	mbedtls_chacha20_context *	ctx,
		const unsigned char	key[32]
	)

This function sets the encryption/decryption key.

Note

After using this function, you must also call mbedtls_chacha20_starts() to set a nonce before you start encrypting/decrypting data with mbedtls_chacha_update().

Parameters

ctx	The ChaCha20 context to which the key should be bound. It must be initialized.
key	The encryption/decryption key. This must be 32 Bytes in length.

Returns

0 on success.

MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA if ctx or key is NULL.

mbedtls_chacha20_starts()

int mbedtls_chacha20_starts	(	mbedtls_chacha20_context *	ctx,
		const unsigned char	nonce[12],
		uint32_t	counter
	)

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.

Parameters

ctx	The ChaCha20 context to which the nonce should be bound. It must be initialized and bound to a key.
nonce	The nonce. This must be 12 Bytes in size.
counter	The initial counter value. This is usually 0.

Returns

0 on success.

MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA if ctx or nonce is NULL.

mbedtls_chacha20_update()

int mbedtls_chacha20_update	(	mbedtls_chacha20_context *	ctx,
		size_t	size,
		const unsigned char *	input,
		unsigned char *	output
	)

This function encrypts or decrypts data.

             Since ChaCha20 is a stream cipher, the same operation is
             used for encrypting and decrypting data.

Note

The input and output pointers must either be equal or point to non-overlapping buffers.

mbedtls_chacha20_setkey() and mbedtls_chacha20_starts() must be called at least once to setup the context before this function can be called.

This function can be called multiple times in a row in order to encrypt of decrypt data piecewise with the same key and nonce.

Parameters

ctx	The ChaCha20 context to use for encryption or decryption. It must be initialized and bound to a key and nonce.
size	The length of the input data in Bytes.
input	The buffer holding the input data. This pointer can be NULL if size == 0.
output	The buffer holding the output data. This must be able to hold size Bytes. This pointer can be NULL if size == 0.

Returns

0 on success.

A negative error code on failure.