Algorithms - ChaCha

Functions
WOLFSSL_API int	wc_Chacha_SetIV (ChaCha *ctx, const byte *inIv, word32 counter)
	This function sets the initialization vector (nonce) for a ChaCha object, initializing it for use as a cipher. It should be called after the key has been set, using wc_Chacha_SetKey. A difference nonce should be used for each round of encryption.
WOLFSSL_API int	wc_Chacha_Process (ChaCha *ctx, byte *cipher, const byte *plain, word32 msglen)
	This function processes the text from the buffer input, encrypts or decrypts it, and stores the result in the buffer output.
WOLFSSL_API int	wc_Chacha_SetKey (ChaCha *ctx, const byte *key, word32 keySz)
	This function sets the key for a ChaCha object, initializing it for use as a cipher. It should be called before setting the nonce with wc_Chacha_SetIV, and before using it for encryption with wc_Chacha_Process.

Detailed Description

Function Documentation

wc_Chacha_Process()

WOLFSSL_API int wc_Chacha_Process	(	ChaCha *	ctx,
		byte *	output,
		const byte *	input,
		word32	msglen )

This function processes the text from the buffer input, encrypts or decrypts it, and stores the result in the buffer output.

Returns

0 Returned upon successfully encrypting or decrypting the input

BAD_FUNC_ARG returned if there is an error processing the ctx input argument

Parameters

ctx	pointer to the ChaCha structure on which to set the iv
output	pointer to a buffer in which to store the output ciphertext or decrypted plaintext
input	pointer to the buffer containing the input plaintext to encrypt or the input ciphertext to decrypt
msglen	length of the message to encrypt or the ciphertext to decrypt

Example

ChaCha enc;
// initialize enc with wc_Chacha_SetKey and wc_Chacha_SetIV
 
byte plain[] = { // initialize plaintext };
byte cipher[sizeof(plain)];
if( wc_Chacha_Process(&enc, cipher, plain, sizeof(plain)) != 0) {
    // error processing ChaCha cipher
}

See also

wc_Chacha_SetKey

wc_Chacha_Process

API to encrypt/decrypt a message of any size.

wc_Chacha_SetIV()

WOLFSSL_API int wc_Chacha_SetIV	(	ChaCha *	ctx,
		const byte *	inIv,
		word32	counter )

This function sets the initialization vector (nonce) for a ChaCha object, initializing it for use as a cipher. It should be called after the key has been set, using wc_Chacha_SetKey. A difference nonce should be used for each round of encryption.

Returns

0 Returned upon successfully setting the initialization vector

BAD_FUNC_ARG returned if there is an error processing the ctx input argument

Parameters

ctx	pointer to the ChaCha structure on which to set the iv
inIv	pointer to a buffer containing the 12 byte initialization vector with which to initialize the ChaCha structure
counter	the value at which the block counter should start–usually zero.

Example

ChaCha enc;
// initialize enc with wc_Chacha_SetKey
byte iv[12];
// initialize iv
if( wc_Chacha_SetIV(&enc, iv, 0) != 0) {
    // error initializing ChaCha structure
}

See also

wc_Chacha_SetKey

wc_Chacha_Process

Set up iv(nonce). Earlier versions used 64 bits instead of 96, this version uses the typical AEAD 96 bit nonce and can do record sizes of 256 GB.

wc_Chacha_SetKey()

WOLFSSL_API int wc_Chacha_SetKey	(	ChaCha *	ctx,
		const byte *	key,
		word32	keySz )

This function sets the key for a ChaCha object, initializing it for use as a cipher. It should be called before setting the nonce with wc_Chacha_SetIV, and before using it for encryption with wc_Chacha_Process.

Returns

0 Returned upon successfully setting the key

BAD_FUNC_ARG returned if there is an error processing the ctx input argument or if the key is not 16 or 32 bytes long

Parameters

ctx	pointer to the ChaCha structure in which to set the key
key	pointer to a buffer containing the 16 or 32 byte key with which to initialize the ChaCha structure
keySz	the length of the key passed in

Example

ChaCha enc;
byte key[] = { // initialize key };
 
if( wc_Chacha_SetKey(&enc, key, sizeof(key)) != 0) {
    // error initializing ChaCha structure
}

See also

wc_Chacha_SetIV

wc_Chacha_Process

Key setup. 8 word iv (nonce)