ocrypto_chacha20_poly1305_encrypt()

void ocrypto_chacha20_poly1305_encrypt	(	uint8_t	tag[(16)],
		uint8_t *	c,
		const uint8_t *	m,
		size_t	m_len,
		const uint8_t *	a,
		size_t	a_len,
		const uint8_t *	n,
		size_t	n_len,
		const uint8_t	k[(32)] )

#include <crypto/nrf_oberon/include/ocrypto_chacha20_poly1305.h>

AEAD ChaCha20-Poly1305 encrypt.

The message m is encrypted using a ChaCha20 cipher stream derived from the encryption key k and the nonce n. The resulting ciphertext has the same length m_len as the input message m and is put into c.

Additionally, the ciphertext c, as well as the additional authenticated data a, is authenticated with a tag that is generated with Poly1305 using a unique subkey derived from k and n, and then put into tag.

Parameters

[out]	tag	Generated authentication tag.
[out]	c	Generated ciphertext. Same length as input message.
	m	Input message.
	m_len	Length of m and c.
	a	Additional authenticated data.
	a_len	Length of a. May be 0.
	n	Nonce (or IV).
	n_len	Length of n. n_len = 8, 12, or 24.
	k	Encryption key.

Remarks

c may be same as m.

When reusing an encryption key k for a different message m or different additional authenticated data a, a different nonce n must be used.

If n_len = 24, the XChaCha20-Poly1305 algorithm is used.