tc_ctr_prng.c File Reference

#include "tc_ctr_prng.h"
#include "tc_utils.h"
#include "tc_constants.h"
#include <string.h>

Functions
static void	arrInc (uint8_t arr[], unsigned int len)
	Array incrementer Treats the supplied array as one contiguous number (MSB in arr[0]), and increments it by one. More...
static void	tc_ctr_prng_update (TCCtrPrng_t *const ctx, uint8_t const *const providedData)
	CTR PRNG update Updates the internal state of supplied the CTR PRNG context increments it by one. More...
int	tc_ctr_prng_init (TCCtrPrng_t *const ctx, uint8_t const *const entropy, unsigned int entropyLen, uint8_t const *const personalization, unsigned int pLen)
	CTR-PRNG initialization procedure Initializes prng context with entropy and personalization string (if any) More...
int	tc_ctr_prng_reseed (TCCtrPrng_t *const ctx, uint8_t const *const entropy, unsigned int entropyLen, uint8_t const *const additional_input, unsigned int additionallen)
	CTR-PRNG reseed procedure Mixes entropy and additional_input into the prng context. More...
int	tc_ctr_prng_generate (TCCtrPrng_t *const ctx, uint8_t const *const additional_input, unsigned int additionallen, uint8_t *const out, unsigned int outlen)
	CTR-PRNG generate procedure Generates outlen pseudo-random bytes into out buffer, updates prng. More...
void	tc_ctr_prng_uninstantiate (TCCtrPrng_t *const ctx)
	CTR-PRNG uninstantiate procedure Zeroes the internal state of the supplied prng context. More...

Function Documentation

arrInc()

static void arrInc ( uint8_t  arr[], unsigned int  len  )

static

Array incrementer Treats the supplied array as one contiguous number (MSB in arr[0]), and increments it by one.

Returns

none

Parameters

arr	IN/OUT – array to be incremented
len	IN – size of arr in bytes

tc_ctr_prng_generate()

int tc_ctr_prng_generate	(	TCCtrPrng_t *const	ctx,
		uint8_t const *const	additional_input,
		unsigned int	additionallen,
		uint8_t *const	out,
		unsigned int	outlen
	)

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

Returns

returns TC_CRYPTO_SUCCESS (1) returns TC_CTR_PRNG_RESEED_REQ (-1) if a reseed is needed returns TC_CRYPTO_FAIL (0) if: ctx == NULL, out == NULL, outlen >= 2^16

Note

Assumes tc_ctr_prng_init has been called for ctx

Parameters

ctx	IN/OUT – the PRNG context
additional_input	IN – additional input to the prng (may be null)
additionallen	IN – additional input length in bytes
out	IN/OUT – buffer to receive output
outlen	IN – size of out buffer in bytes

tc_ctr_prng_init()

int tc_ctr_prng_init	(	TCCtrPrng_t *const	ctx,
		uint8_t const *const	entropy,
		unsigned int	entropyLen,
		uint8_t const *const	personalization,
		unsigned int	pLen
	)

CTR-PRNG initialization procedure Initializes prng context with entropy and personalization string (if any)

Returns

returns TC_CRYPTO_SUCCESS (1) returns TC_CRYPTO_FAIL (0) if: ctx == NULL, entropy == NULL, entropyLen < (TC_AES_KEY_SIZE + TC_AES_BLOCK_SIZE)

Note

Only the first (TC_AES_KEY_SIZE + TC_AES_BLOCK_SIZE) bytes of both the entropy and personalization inputs are used - supplying additional bytes has no effect.

Parameters

ctx	IN/OUT – the PRNG context to initialize
entropy	IN – entropy used to seed the PRNG
entropyLen	IN – entropy length in bytes
personalization	IN – personalization string used to seed the PRNG (may be null)
plen	IN – personalization length in bytes

tc_ctr_prng_reseed()

int tc_ctr_prng_reseed	(	TCCtrPrng_t *const	ctx,
		uint8_t const *const	entropy,
		unsigned int	entropyLen,
		uint8_t const *const	additional_input,
		unsigned int	additionallen
	)

CTR-PRNG reseed procedure Mixes entropy and additional_input into the prng context.

Returns

returns TC_CRYPTO_SUCCESS (1) returns TC_CRYPTO_FAIL (0) if: ctx == NULL, entropy == NULL, entropylen < (TC_AES_KEY_SIZE + TC_AES_BLOCK_SIZE)

Note

It is better to reseed an existing prng context rather than re-initialise, so that any existing entropy in the context is presereved. This offers some protection against undetected failures of the entropy source.

Assumes tc_ctr_prng_init has been called for ctx

Parameters

ctx	IN/OUT – the PRNG state
entropy	IN – entropy to mix into the prng
entropylen	IN – length of entropy in bytes
additional_input	IN – additional input to the prng (may be null)
additionallen	IN – additional input length in bytes

tc_ctr_prng_uninstantiate()

void tc_ctr_prng_uninstantiate

(

TCCtrPrng_t *const

ctx

)

CTR-PRNG uninstantiate procedure Zeroes the internal state of the supplied prng context.

Returns

none

Parameters

ctx	IN/OUT – the PRNG context

tc_ctr_prng_update()

static void tc_ctr_prng_update ( TCCtrPrng_t *const  ctx, uint8_t const *const  providedData  )

static

CTR PRNG update Updates the internal state of supplied the CTR PRNG context increments it by one.

Returns

none

Note

Assumes: providedData is (TC_AES_KEY_SIZE + TC_AES_BLOCK_SIZE) bytes long

Parameters

ctx	IN/OUT – CTR PRNG state
providedData	IN – data used when updating the internal state