tc_ccm_mode.c File Reference

#include "tc_ccm_mode.h"
#include "tc_constants.h"
#include "tc_utils.h"
#include <stdio.h>

Functions
int	tc_ccm_config (TCCcmMode_t c, TCAesKeySched_t sched, uint8_t *nonce, unsigned int nlen, unsigned int mlen)
	CCM configuration procedure. More...
static void	ccm_cbc_mac (uint8_t *T, const uint8_t *data, unsigned int dlen, unsigned int flag, TCAesKeySched_t sched)
	Variation of CBC-MAC mode used in CCM. More...
static int	ccm_ctr_mode (uint8_t *out, unsigned int outlen, const uint8_t *in, unsigned int inlen, uint8_t *ctr, const TCAesKeySched_t sched)
	Variation of CTR mode used in CCM. More...
int	tc_ccm_generation_encryption (uint8_t *out, unsigned int olen, const uint8_t *associated_data, unsigned int alen, const uint8_t *payload, unsigned int plen, TCCcmMode_t c)
	CCM tag generation and encryption procedure. More...
int	tc_ccm_decryption_verification (uint8_t *out, unsigned int olen, const uint8_t *associated_data, unsigned int alen, const uint8_t *payload, unsigned int plen, TCCcmMode_t c)
	CCM decryption and tag verification procedure. More...

Function Documentation

ccm_cbc_mac()

static void ccm_cbc_mac ( uint8_t *  T, const uint8_t *  data, unsigned int  dlen, unsigned int  flag, TCAesKeySched_t  sched  )

static

Variation of CBC-MAC mode used in CCM.

ccm_ctr_mode()

static int ccm_ctr_mode ( uint8_t *  out, unsigned int  outlen, const uint8_t *  in, unsigned int  inlen, uint8_t *  ctr, const TCAesKeySched_t  sched  )

static

Variation of CTR mode used in CCM.

The CTR mode used by CCM is slightly different than the conventional CTR mode (the counter is increased before encryption, instead of after encryption). Besides, it is assumed that the counter is stored in the last 2 bytes of the nonce.

tc_ccm_config()

int tc_ccm_config	(	TCCcmMode_t	c,
		TCAesKeySched_t	sched,
		uint8_t *	nonce,
		unsigned int	nlen,
		unsigned int	mlen
	)

CCM configuration procedure.

Returns

returns TC_CRYPTO_SUCCESS (1) returns TC_CRYPTO_FAIL (0) if: c == NULL or sched == NULL or nonce == NULL or mlen != {4, 6, 8, 10, 12, 16}

Parameters

c	– CCM state
sched	IN – AES key schedule
nonce	IN - nonce
nlen	– nonce length in bytes
mlen	– mac length in bytes (parameter t in SP-800 38C)

tc_ccm_decryption_verification()

int tc_ccm_decryption_verification	(	uint8_t *	out,
		unsigned int	olen,
		const uint8_t *	associated_data,
		unsigned int	alen,
		const uint8_t *	payload,
		unsigned int	plen,
		TCCcmMode_t	c
	)

CCM decryption and tag verification procedure.

Returns

returns TC_CRYPTO_SUCCESS (1) returns TC_CRYPTO_FAIL (0) if: out == NULL or c == NULL or ((plen > 0) and (payload == NULL)) or ((alen > 0) and (associated_data == NULL)) or (alen >= TC_CCM_AAD_MAX_BYTES) or (plen >= TC_CCM_PAYLOAD_MAX_BYTES) or (olen < plen - c->mlen)

Parameters

out	OUT – decrypted data
associated_data	IN – associated data
alen	IN – associated data length in bytes
payload	IN – payload
plen	IN – payload length in bytes
c	IN – CCM state

Note

: out buffer should be at least (plen - c->mlen) bytes long.

: The sequence b for encryption is formatted as follows: b = [FLAGS | nonce | counter ], where: FLAGS is 1 byte long nonce is 13 bytes long counter is 2 bytes long The byte FLAGS is composed by the following 8 bits: 0-2 bits: used to represent the value of q-1 3-7 btis: always 0's

: The sequence b for authentication is formatted as follows: b = [FLAGS | nonce | length(mac length)], where: FLAGS is 1 byte long nonce is 13 bytes long length(mac length) is 2 bytes long The byte FLAGS is composed by the following 8 bits: 0-2 bits: used to represent the value of q-1 3-5 bits: mac length (encoded as: (mlen-2)/2) 6: Adata (0 if alen == 0, and 1 otherwise) 7: always 0

tc_ccm_generation_encryption()

int tc_ccm_generation_encryption	(	uint8_t *	out,
		unsigned int	olen,
		const uint8_t *	associated_data,
		unsigned int	alen,
		const uint8_t *	payload,
		unsigned int	plen,
		TCCcmMode_t	c
	)

CCM tag generation and encryption procedure.

Returns

returns TC_CRYPTO_SUCCESS (1) returns TC_CRYPTO_FAIL (0) if: out == NULL or c == NULL or ((plen > 0) and (payload == NULL)) or ((alen > 0) and (associated_data == NULL)) or (alen >= TC_CCM_AAD_MAX_BYTES) or (plen >= TC_CCM_PAYLOAD_MAX_BYTES) or (olen < plen + maclength)

Parameters

out	OUT – encrypted data
olen	IN – output length in bytes
associated_data	IN – associated data
alen	IN – associated data length in bytes
payload	IN – payload
plen	IN – payload length in bytes
c	IN – CCM state

Note

: out buffer should be at least (plen + c->mlen) bytes long.

: The sequence b for encryption is formatted as follows: b = [FLAGS | nonce | counter ], where: FLAGS is 1 byte long nonce is 13 bytes long counter is 2 bytes long The byte FLAGS is composed by the following 8 bits: 0-2 bits: used to represent the value of q-1 3-7 btis: always 0's

: The sequence b for authentication is formatted as follows: b = [FLAGS | nonce | length(mac length)], where: FLAGS is 1 byte long nonce is 13 bytes long length(mac length) is 2 bytes long The byte FLAGS is composed by the following 8 bits: 0-2 bits: used to represent the value of q-1 3-5 bits: mac length (encoded as: (mlen-2)/2) 6: Adata (0 if alen == 0, and 1 otherwise) 7: always 0