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chacha20.h File Reference
Functions

chacha20.h File Reference

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

Go to the source code of this file.

Functions

void mbedtls_chacha20_init (mbedtls_chacha20_context *ctx)
 This function initializes the specified ChaCha20 context.
void mbedtls_chacha20_free (mbedtls_chacha20_context *ctx)
 This function releases and clears the specified ChaCha20 context.
int mbedtls_chacha20_setkey (mbedtls_chacha20_context *ctx, const unsigned char key[32])
 This function sets the encryption/decryption key.
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.
int mbedtls_chacha20_update (mbedtls_chacha20_context *ctx, size_t size, const unsigned char *input, unsigned char *output)
 This function encrypts or decrypts data.
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.
int mbedtls_chacha20_self_test (int verbose)
 The ChaCha20 checkup routine.

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 <damaki.gh@gmail.com>

Definition in file chacha20.h.

Function Documentation

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:
keyThe encryption/decryption key. This must be 32 Bytes in length.
nonceThe nonce. This must be 12 Bytes in size.
counterThe initial counter value. This is usually 0.
sizeThe length of the input data in Bytes.
inputThe buffer holding the input data. This pointer can be NULL if `size == 0`.
outputThe 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.

Definition at line 320 of file chacha20.c.

void mbedtls_chacha20_free ( mbedtls_chacha20_context *  ctx )

This function releases and clears the specified ChaCha20 context.

Parameters:
ctxThe 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.

Definition at line 199 of file chacha20.c.

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 mbedtls_chacha20_setkey() and mbedtls_chacha20_starts(), then one or more calls to to mbedtls_chacha20_update(), and finally to mbedtls_chacha20_free().

Parameters:
ctxThe ChaCha20 context to initialize. This must not be NULL.

Definition at line 188 of file chacha20.c.

int mbedtls_chacha20_self_test ( int  verbose )

The ChaCha20 checkup routine.

Returns:
0 on success.
1 on failure.

Definition at line 535 of file chacha20.c.

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:
ctxThe ChaCha20 context to which the key should be bound. It must be initialized.
keyThe 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.

Definition at line 207 of file chacha20.c.

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:
ctxThe ChaCha20 context to which the nonce should be bound. It must be initialized and bound to a key.
nonceThe nonce. This must be 12 Bytes in size.
counterThe initial counter value. This is usually 0.
Returns:
0 on success.
MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA if ctx or nonce is NULL.

Definition at line 232 of file chacha20.c.

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:
ctxThe ChaCha20 context to use for encryption or decryption. It must be initialized and bound to a key and nonce.
sizeThe length of the input data in Bytes.
inputThe buffer holding the input data. This pointer can be NULL if `size == 0`.
outputThe 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.

Definition at line 255 of file chacha20.c.

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