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.

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.

Calling the function a second time with the generated ciphertext as input message m decrypts it back to the original message.

Parameters

[out]	c	Generated ciphertext. Same length as input message.
	m	Input message.
	m_len	Length of c and m.
	n	Nonce.
	n_len	Nonce length. 0 <= n_len <= ocrypto_chacha20_NONCE_BYTES_MAX.
	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.