chacha.h

Functions

	Name
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.
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.
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.

Functions Documentation

function wc_Chacha_SetIV

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.

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.

See:

• wc_Chacha_SetKey
• wc_Chacha_Process

Return:

• 0 Returned upon successfully setting the initialization vector
• BAD_FUNC_ARG returned if there is an error processing the ctx input argument

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
}

function wc_Chacha_Process

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.

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

See:

• wc_Chacha_SetKey
• wc_Chacha_Process

Return:

• 0 Returned upon successfully encrypting or decrypting the input
• BAD_FUNC_ARG returned if there is an error processing the ctx input argument

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
}

function wc_Chacha_SetKey

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.

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

See:

• wc_Chacha_SetIV
• wc_Chacha_Process

Return:

• 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

Example

ChaCha enc;
byte key[] = { // initialize key };

if( wc_Chacha_SetKey(&enc, key, sizeof(key)) != 0) {
    // error initializing ChaCha structure
}

Source code

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

int wc_Chacha_Process(ChaCha* ctx, byte* cipher, const byte* plain,
                              word32 msglen);

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

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Updated on 2024-11-07 at 01:17:40 +0000