/*---------------------------------------------------------------------------*/
void
adaptivesec_aead(uint8_t *key, int shall_encrypt, uint8_t *result, int forward)
{
uint8_t nonce[CCM_STAR_NONCE_LENGTH];
uint8_t *m;
uint8_t m_len;
uint8_t *a;
uint8_t a_len;
ccm_star_packetbuf_set_nonce(nonce, forward);
a = packetbuf_hdrptr();
if(shall_encrypt) {
#if AKES_NBR_WITH_GROUP_KEYS && PACKETBUF_WITH_UNENCRYPTED_BYTES
a_len = packetbuf_hdrlen() + packetbuf_attr(PACKETBUF_ATTR_UNENCRYPTED_BYTES);
#else /* AKES_NBR_WITH_GROUP_KEYS && PACKETBUF_WITH_UNENCRYPTED_BYTES */
a_len = packetbuf_hdrlen();
#endif /* AKES_NBR_WITH_GROUP_KEYS && PACKETBUF_WITH_UNENCRYPTED_BYTES */
m = a + a_len;
m_len = packetbuf_totlen() - a_len;
} else {
a_len = packetbuf_totlen();
m = NULL;
m_len = 0;
}
AES_128_GET_LOCK();
ADAPTIVESEC_SET_KEY(key);
CCM_STAR.aead(nonce,
m, m_len,
a, a_len,
result, adaptivesec_mic_len(),
forward);
AES_128_RELEASE_LOCK();
}
/*
* We use AES-128 as a key derivation function (KDF). This is possible due to
* simple circumstances. Speaking in terms of the extract-then-expand paradigm
* [RFC 5869], we can skip over the extraction step since we already have a
* uniformly-distributed key which we want to expand into session keys. For
* implementing the expansion step, we may just use AES-128 [Paar and Pelzl,
* Understanding Cryptography].
*/
static void
generate_pairwise_key(uint8_t *result, uint8_t *shared_secret)
{
AES_128_GET_LOCK();
AES_128.set_key(shared_secret);
AES_128.encrypt(result);
AES_128_RELEASE_LOCK();
}
/*
* We use output feedback mode (OFB) for generating cryptographic pseudo-random
* numbers [RFC 4086]. A potential problem with OFB is that OFB at some point
* enters a cycle. However, the expected cycle length given a random key and a
* random starting point is about 2^127 in our instantiation [Davies and Parkin,
* The Average Cycle Size of The Key Stream in Output Feedback Encipherment].
*/
void
csprng_rand(uint8_t *result, uint8_t len)
{
uint16_t pos;
AES_128_GET_LOCK();
AES_128.set_key(seed.key);
for(pos = 0; pos < len; pos += 16) {
AES_128.encrypt(seed.state);
memcpy(result + pos, seed.state, MIN(len - pos, 16));
}
AES_128_RELEASE_LOCK();
}
