ocrypto_chacha20_init()

void ocrypto_chacha20_init	(	ocrypto_chacha20_ctx *	ctx,
		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 encoder/decoder initialization.

The generator state ctx is initialized by this function.

Parameters

[out]	ctx	Encoder/decoder state.
	n	Nonce (or IV). May be NULL.
	n_len	Nonce length. n_len = 8, 12, or 24.
	key	Authentication key. May be NULL.
	count	Initial block counter, usually 0 or 1.

Remarks

If key is NULL only n and count are set. If n is NULL only key is set. Both key and n must be set before update is called.

If n_len = 24, the XChaCha20 algorithm is used.

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