File chacha20.h
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
Defines
-
MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA
Invalid input parameter(s).
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.
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
.
-
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 notNULL
, it must point to an initialized context.
-
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 withmbedtls_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.- Returns:
MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA if ctx or key is NULL.
-
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.- Returns:
MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA if ctx or nonce is NULL.
-
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
andoutput
pointers must either be equal or point to non-overlapping buffers.Note
mbedtls_chacha20_setkey()
andmbedtls_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.
- 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
ifsize == 0
.output – The buffer holding the output data. This must be able to hold
size
Bytes. This pointer can beNULL
ifsize == 0
.
- Returns:
0
on success.- Returns:
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)
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.
Note
The
input
andoutput
pointers must either be equal or point to non-overlapping buffers.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.
- 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
ifsize == 0
.output – The buffer holding the output data. This must be able to hold
size
Bytes. This pointer can beNULL
ifsize == 0
.
- Returns:
0
on success.- Returns:
A negative error code on failure.
-
int mbedtls_chacha20_self_test(int verbose)
The ChaCha20 checkup routine.
- Returns:
0
on success.- Returns:
1
on failure.
-
struct mbedtls_chacha20_context
- #include <chacha20.h>