ocrypto_chacha20_encode()

void ocrypto_chacha20_encode	(	uint8_t *	c,
		const uint8_t *	m,
		size_t	m_len,
		const uint8_t *	n,
		size_t	n_len,
		const uint8_t	key[(32)],
		uint32_t	count )

#include <crypto/nrf_oberon/include/ocrypto_chacha20.h>

ChaCha20 cipher stream encoder/decoder.

The message m is encrypted by applying the XOR operation with a pseudo random cipher stream derived from the encryption key key, the nonce n, and the initial block counter count.

For decryption, the ciphertext is used as input message m and the resulting decrypted message is written to c.

Parameters

[out]	c	Generated ciphertext. Same length as input message.
	m	Input message.
	m_len	Length of c and m.
	n	Nonce (or IV).
	n_len	Nonce length. n_len = 8, 12, or 24.
	key	Encryption key.
	count	Initial block counter.

Remarks

c may be same as m.

When reusing an encryption key key for a different message m, a different nonce n or initial block counter count must be used.

If n_len = 24, the XChaCha20 algorithm is used.