tc_hmac_prng.c File Reference

#include "tc_hmac_prng.h"
#include "tc_hmac.h"
#include "tc_constants.h"
#include "tc_utils.h"

Functions
static void	update (TCHmacPrng_t prng, const uint8_t *e, unsigned int len)
int	tc_hmac_prng_init (TCHmacPrng_t prng, const uint8_t *personalization, unsigned int plen)
	HMAC-PRNG initialization procedure Initializes prng with personalization, disables tc_hmac_prng_generate. More...
int	tc_hmac_prng_reseed (TCHmacPrng_t prng, const uint8_t *seed, unsigned int seedlen, const uint8_t *additional_input, unsigned int additionallen)
	HMAC-PRNG reseed procedure Mixes seed into prng, enables tc_hmac_prng_generate. More...
int	tc_hmac_prng_generate (uint8_t *out, unsigned int outlen, TCHmacPrng_t prng)
	HMAC-PRNG generate procedure Generates outlen pseudo-random bytes into out buffer, updates prng. More...

Variables
static const unsigned int	MIN_SLEN = 32
static const unsigned int	MAX_SLEN = UINT32_MAX
static const unsigned int	MAX_PLEN = UINT32_MAX
static const unsigned int	MAX_ALEN = UINT32_MAX
static const unsigned int	MAX_GENS = UINT32_MAX
static const unsigned int	MAX_OUT = (1 << 19)

Function Documentation

tc_hmac_prng_generate()

int tc_hmac_prng_generate	(	uint8_t *	out,
		unsigned int	outlen,
		TCHmacPrng_t	prng
	)

HMAC-PRNG generate procedure Generates outlen pseudo-random bytes into out buffer, updates prng.

Returns

returns TC_CRYPTO_SUCCESS (1) returns TC_HMAC_PRNG_RESEED_REQ (-1) if a reseed is needed returns TC_CRYPTO_FAIL (0) if: out == NULL, prng == NULL, outlen == 0, outlen >= MAX_OUT

Note

Assumes tc_hmac_prng_init has been called for prng

Parameters

out	IN/OUT – buffer to receive output
outlen	IN – size of out buffer in bytes
prng	IN/OUT – the PRNG state

tc_hmac_prng_init()

int tc_hmac_prng_init	(	TCHmacPrng_t	prng,
		const uint8_t *	personalization,
		unsigned int	plen
	)

HMAC-PRNG initialization procedure Initializes prng with personalization, disables tc_hmac_prng_generate.

Returns

returns TC_CRYPTO_SUCCESS (1) returns TC_CRYPTO_FAIL (0) if: prng == NULL, personalization == NULL, plen > MAX_PLEN

Note

Assumes: - personalization != NULL. The personalization is a platform unique string (e.g., the host name) and is the last line of defense against failure of the entropy source

Warning

NIST SP 800-90A specifies 3 items as seed material during initialization: entropy seed, personalization, and an optional nonce. TinyCrypts requires instead a non-null personalization (which is easily computed) and indirectly requires an entropy seed (since the reseed function is mandatorily called after init)

Parameters

prng	IN/OUT – the PRNG state to initialize
personalization	IN – personalization string
plen	IN – personalization length in bytes

tc_hmac_prng_reseed()

int tc_hmac_prng_reseed	(	TCHmacPrng_t	prng,
		const uint8_t *	seed,
		unsigned int	seedlen,
		const uint8_t *	additional_input,
		unsigned int	additionallen
	)

HMAC-PRNG reseed procedure Mixes seed into prng, enables tc_hmac_prng_generate.

Returns

returns TC_CRYPTO_SUCCESS (1) returns TC_CRYPTO_FAIL (0) if: prng == NULL, seed == NULL, seedlen < MIN_SLEN, seendlen > MAX_SLEN, additional_input != (const uint8_t *) 0 && additionallen == 0, additional_input != (const uint8_t *) 0 && additionallen > MAX_ALEN

Note

Assumes:- tc_hmac_prng_init has been called for prng

• seed has sufficient entropy.

Parameters

prng	IN/OUT – the PRNG state
seed	IN – entropy to mix into the prng
seedlen	IN – length of seed in bytes
additional_input	IN – additional input to the prng
additionallen	IN – additional input length in bytes

update()

static void update ( TCHmacPrng_t  prng, const uint8_t *  e, unsigned int  len  )

static

Variable Documentation

MAX_ALEN

const unsigned int MAX_ALEN = UINT32_MAX

static

MAX_GENS

const unsigned int MAX_GENS = UINT32_MAX

static

MAX_OUT

const unsigned int MAX_OUT = (1 << 19)

static

MAX_PLEN

const unsigned int MAX_PLEN = UINT32_MAX

static

MAX_SLEN

const unsigned int MAX_SLEN = UINT32_MAX

static

MIN_SLEN

const unsigned int MIN_SLEN = 32

static