This file contains the AEAD-ChaCha20-Poly1305 definitions and functions. More...

#include "config.h"
#include "poly1305.h"
#include "chacha20.h"

Include dependency graph for chachapoly.h:

Data Structures
struct	mbedtls_chachapoly_context

Macros
#define	MBEDTLS_ERR_CHACHAPOLY_BAD_STATE -0x0054
	The requested operation is not permitted in the current state. More...

#define	MBEDTLS_ERR_CHACHAPOLY_AUTH_FAILED -0x0056
	Authenticated decryption failed: data was not authentic. More...

Typedefs
typedef struct mbedtls_chachapoly_context	mbedtls_chachapoly_context

Enumerations
enum	mbedtls_chachapoly_mode_t { MBEDTLS_CHACHAPOLY_ENCRYPT, MBEDTLS_CHACHAPOLY_DECRYPT }

Functions
void	mbedtls_chachapoly_init (mbedtls_chachapoly_context *ctx)
	This function initializes the specified ChaCha20-Poly1305 context. More...

void	mbedtls_chachapoly_free (mbedtls_chachapoly_context *ctx)
	This function releases and clears the specified ChaCha20-Poly1305 context. More...

int	mbedtls_chachapoly_setkey (mbedtls_chachapoly_context *ctx, const unsigned char key[32])
	This function sets the ChaCha20-Poly1305 symmetric encryption key. More...

int	mbedtls_chachapoly_starts (mbedtls_chachapoly_context *ctx, const unsigned char nonce[12], mbedtls_chachapoly_mode_t mode)
	This function starts a ChaCha20-Poly1305 encryption or decryption operation. More...

int	mbedtls_chachapoly_update_aad (mbedtls_chachapoly_context ctx, const unsigned char aad, size_t aad_len)
	This function feeds additional data to be authenticated into an ongoing ChaCha20-Poly1305 operation. More...

int	mbedtls_chachapoly_update (mbedtls_chachapoly_context ctx, size_t len, const unsigned char input, unsigned char *output)
	Thus function feeds data to be encrypted or decrypted into an on-going ChaCha20-Poly1305 operation. More...

int	mbedtls_chachapoly_finish (mbedtls_chachapoly_context *ctx, unsigned char mac[16])
	This function finished the ChaCha20-Poly1305 operation and generates the MAC (authentication tag). More...

int	mbedtls_chachapoly_encrypt_and_tag (mbedtls_chachapoly_context ctx, size_t length, const unsigned char nonce[12], const unsigned char aad, size_t aad_len, const unsigned char input, unsigned char output, unsigned char tag[16])
	This function performs a complete ChaCha20-Poly1305 authenticated encryption with the previously-set key. More...

int	mbedtls_chachapoly_auth_decrypt (mbedtls_chachapoly_context ctx, size_t length, const unsigned char nonce[12], const unsigned char aad, size_t aad_len, const unsigned char tag[16], const unsigned char input, unsigned char output)
	This function performs a complete ChaCha20-Poly1305 authenticated decryption with the previously-set key. More...

int	mbedtls_chachapoly_self_test (int verbose)
	The ChaCha20-Poly1305 checkup routine. More...

Detailed Description

This file contains the AEAD-ChaCha20-Poly1305 definitions and functions.

ChaCha20-Poly1305 is an algorithm for Authenticated Encryption with Associated Data (AEAD) that can be used to encrypt and authenticate data. It is based on ChaCha20 and Poly1305 by Daniel Bernstein and was standardized in RFC 7539.

Author: Daniel King damak.nosp@m.i.gh.nosp@m.@gmai.nosp@m.l.co.nosp@m.m

Definition in file chachapoly.h.

Macro Definition Documentation

#define MBEDTLS_ERR_CHACHAPOLY_AUTH_FAILED -0x0056

Authenticated decryption failed: data was not authentic.

Definition at line 46 of file chachapoly.h.

#define MBEDTLS_ERR_CHACHAPOLY_BAD_STATE -0x0054

The requested operation is not permitted in the current state.

Definition at line 45 of file chachapoly.h.

Typedef Documentation

typedef struct mbedtls_chachapoly_context mbedtls_chachapoly_context

Enumeration Type Documentation

enum mbedtls_chachapoly_mode_t

Enumerator
MBEDTLS_CHACHAPOLY_ENCRYPT	The mode value for performing encryption.
MBEDTLS_CHACHAPOLY_DECRYPT	The mode value for performing decryption.

Definition at line 52 of file chachapoly.h.

Function Documentation

int mbedtls_chachapoly_auth_decrypt	(	mbedtls_chachapoly_context *	ctx,
		size_t	length,
		const unsigned char	nonce[12],
		const unsigned char *	aad,
		size_t	aad_len,
		const unsigned char	tag[16],
		const unsigned char *	input,
		unsigned char *	output
	)

This function performs a complete ChaCha20-Poly1305 authenticated decryption with the previously-set key.

Note: Before using this function, you must set the key with mbedtls_chachapoly_setkey().

Parameters

ctx	The ChaCha20-Poly1305 context to use (holds the key).
length	The length (in Bytes) of the data to decrypt.
nonce	The `96` Bit (`12` bytes) nonce/IV to use.
aad	The buffer containing the additional authenticated data (AAD). This pointer can be `NULL` if `aad_len == 0`.
aad_len	The length (in bytes) of the AAD data to process.
tag	The buffer holding the authentication tag. This must be a readable buffer of length `16` Bytes.
input	The buffer containing the data to decrypt. This pointer can be `NULL` if `ilen == 0`.
output	The buffer to where the decrypted data is written. This pointer can be `NULL` if `ilen == 0`.

Returns: 0 on success.; MBEDTLS_ERR_CHACHAPOLY_AUTH_FAILED if the data was not authentic.; Another negative error code on other kinds of failure.

int mbedtls_chachapoly_encrypt_and_tag	(	mbedtls_chachapoly_context *	ctx,
		size_t	length,
		const unsigned char	nonce[12],
		const unsigned char *	aad,
		size_t	aad_len,
		const unsigned char *	input,
		unsigned char *	output,
		unsigned char	tag[16]
	)

This function performs a complete ChaCha20-Poly1305 authenticated encryption with the previously-set key.

Note: Before using this function, you must set the key with mbedtls_chachapoly_setkey().

Warning: You must never use the same nonce twice with the same key. This would void any confidentiality and authenticity guarantees for the messages encrypted with the same nonce and key.

Parameters

ctx	The ChaCha20-Poly1305 context to use (holds the key). This must be initialized.
length	The length (in bytes) of the data to encrypt or decrypt.
nonce	The 96-bit (12 bytes) nonce/IV to use.
aad	The buffer containing the additional authenticated data (AAD). This pointer can be `NULL` if `aad_len == 0`.
aad_len	The length (in bytes) of the AAD data to process.
input	The buffer containing the data to encrypt or decrypt. This pointer can be `NULL` if `ilen == 0`.
output	The buffer to where the encrypted or decrypted data is written. This pointer can be `NULL` if `ilen == 0`.
tag	The buffer to where the computed 128-bit (16 bytes) MAC is written. This must not be `NULL`.

Returns: 0 on success.; A negative error code on failure.

int mbedtls_chachapoly_finish	(	mbedtls_chachapoly_context *	ctx,
		unsigned char	mac[16]
	)

This function finished the ChaCha20-Poly1305 operation and generates the MAC (authentication tag).

Parameters

ctx	The ChaCha20-Poly1305 context to use. This must be initialized.
mac	The buffer to where the 128-bit (16 bytes) MAC is written.

Warning: Decryption with the piecewise API is discouraged, see the warning on mbedtls_chachapoly_init().

Returns: 0 on success.; MBEDTLS_ERR_CHACHAPOLY_BAD_STATE if the operation has not been started or has been finished.; Another negative error code on other kinds of failure.

void mbedtls_chachapoly_free ( mbedtls_chachapoly_context * ctx )

This function releases and clears the specified ChaCha20-Poly1305 context.

Parameters

ctx	The ChachaPoly context to clear. This may be `NULL`, in which case this function is a no-op.

void mbedtls_chachapoly_init ( mbedtls_chachapoly_context * ctx )

This function initializes the specified ChaCha20-Poly1305 context.

It must be the first API called before using the context. It must be followed by a call to mbedtls_chachapoly_setkey() before any operation can be done, and to mbedtls_chachapoly_free() once all operations with that context have been finished.

In order to encrypt or decrypt full messages at once, for each message you should make a single call to mbedtls_chachapoly_crypt_and_tag() or mbedtls_chachapoly_auth_decrypt().

In order to encrypt messages piecewise, for each message you should make a call to mbedtls_chachapoly_starts(), then 0 or more calls to mbedtls_chachapoly_update_aad(), then 0 or more calls to mbedtls_chachapoly_update(), then one call to mbedtls_chachapoly_finish().

Warning: Decryption with the piecewise API is discouraged! Always use mbedtls_chachapoly_auth_decrypt() when possible!

If however this is not possible because the data is too large to fit in memory, you need to:

call mbedtls_chachapoly_starts() and (if needed) mbedtls_chachapoly_update_aad() as above,
call mbedtls_chachapoly_update() multiple times and ensure its output (the plaintext) is NOT used in any other way than placing it in temporary storage at this point,
call mbedtls_chachapoly_finish() to compute the authentication tag and compared it in constant time to the tag received with the ciphertext.

If the tags are not equal, you must immediately discard all previous outputs of mbedtls_chachapoly_update(), otherwise you can now safely use the plaintext.

Parameters

ctx	The ChachaPoly context to initialize. Must not be `NULL`.

int mbedtls_chachapoly_self_test ( int verbose )

The ChaCha20-Poly1305 checkup routine.

Returns: 0 on success.; 1 on failure.

int mbedtls_chachapoly_setkey	(	mbedtls_chachapoly_context *	ctx,
		const unsigned char	key[32]
	)

This function sets the ChaCha20-Poly1305 symmetric encryption key.

Parameters

ctx	The ChaCha20-Poly1305 context to which the key should be bound. This must be initialized.
key	The `256` Bit (`32` Bytes) key.

Returns: 0 on success.; A negative error code on failure.

int mbedtls_chachapoly_starts	(	mbedtls_chachapoly_context *	ctx,
		const unsigned char	nonce[12],
		mbedtls_chachapoly_mode_t	mode
	)

This function starts a ChaCha20-Poly1305 encryption or decryption operation.

Warning: You must never use the same nonce twice with the same key. This would void any confidentiality and authenticity guarantees for the messages encrypted with the same nonce and key.

Note: If the context is being used for AAD only (no data to encrypt or decrypt) then mode can be set to any value.

Warning: Decryption with the piecewise API is discouraged, see the warning on mbedtls_chachapoly_init().

Parameters

ctx	The ChaCha20-Poly1305 context. This must be initialized and bound to a key.
nonce	The nonce/IV to use for the message. This must be a redable buffer of length `12` Bytes.
mode	The operation to perform: MBEDTLS_CHACHAPOLY_ENCRYPT or MBEDTLS_CHACHAPOLY_DECRYPT (discouraged, see warning).

Returns: 0 on success.; A negative error code on failure.

int mbedtls_chachapoly_update	(	mbedtls_chachapoly_context *	ctx,
		size_t	len,
		const unsigned char *	input,
		unsigned char *	output
	)

Thus function feeds data to be encrypted or decrypted into an on-going ChaCha20-Poly1305 operation.

The direction (encryption or decryption) depends on the mode that was given when calling mbedtls_chachapoly_starts().

You may call this function multiple times to process an arbitrary amount of data. It is permitted to call this function 0 times, if no data is to be encrypted or decrypted.

Warning: Decryption with the piecewise API is discouraged, see the warning on mbedtls_chachapoly_init().

Parameters

ctx	The ChaCha20-Poly1305 context to use. This must be initialized.
len	The length (in bytes) of the data to encrypt or decrypt.
input	The buffer containing the data to encrypt or decrypt. This pointer can be `NULL` if `len == 0`.
output	The buffer to where the encrypted or decrypted data is written. This must be able to hold `len` bytes. This pointer can be `NULL` if `len == 0`.

Returns: 0 on success.; MBEDTLS_ERR_CHACHAPOLY_BAD_STATE if the operation has not been started or has been finished.; Another negative error code on other kinds of failure.

int mbedtls_chachapoly_update_aad	(	mbedtls_chachapoly_context *	ctx,
		const unsigned char *	aad,
		size_t	aad_len
	)

This function feeds additional data to be authenticated into an ongoing ChaCha20-Poly1305 operation.

The Additional Authenticated Data (AAD), also called Associated Data (AD) is only authenticated but not encrypted nor included in the encrypted output. It is usually transmitted separately from the ciphertext or computed locally by each party.

Note: This function is called before data is encrypted/decrypted. I.e. call this function to process the AAD before calling mbedtls_chachapoly_update().

You may call this function multiple times to process an arbitrary amount of AAD. It is permitted to call this function 0 times, if no AAD is used.

This function cannot be called any more if data has been processed by mbedtls_chachapoly_update(), or if the context has been finished.

Warning: Decryption with the piecewise API is discouraged, see the warning on mbedtls_chachapoly_init().

Parameters

ctx	The ChaCha20-Poly1305 context. This must be initialized and bound to a key.
aad_len	The length in Bytes of the AAD. The length has no restrictions.
aad	Buffer containing the AAD. This pointer can be `NULL` if `aad_len == 0`.

Returns: 0 on success.; MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA if ctx or aad are NULL.; MBEDTLS_ERR_CHACHAPOLY_BAD_STATE if the operations has not been started or has been finished, or if the AAD has been finished.

API Documentation (Doxygen generated)

Data Structures

Macros

Typedefs

Enumerations

Functions

Detailed Description

Macro Definition Documentation

Typedef Documentation

Enumeration Type Documentation

Function Documentation