RNGA: Random Number Generator Accelerator Driver

Overview

The Kinetis SDK provides Peripheral driver for the Random Number Generator Accelerator (RNGA) block of Kinetis devices.

RNGA Initialization

1. To initialize the RNGA module, call the RNGA_Init() function. This function automatically enables the RNGA module and its clock.
   
2. After calling the RNGA_Init() function, the RNGA is enabled and the counter starts working.
3. To disable the RNGA module, call the RNGA_Deinit() function.

Get random data from RNGA

1. RNGA_GetRandomData() function gets random data from the RNGA module.

RNGA Set/Get Working Mode

The RNGA works either in sleep mode or normal mode

1. RNGA_SetMode() function sets the RNGA mode.
2. RNGA_GetMode() function gets the RNGA working mode.

Seed RNGA

1. RNGA_Seed() function inputs an entropy value that the RNGA can use to seed the pseudo random algorithm.

This example code shows how to initialize and get random data from the RNGA driver:

{
    status_t       status;
    uint32_t       data;

    /* Initialize RNGA 
    status = RNGA_Init(RNG);

    /* Read Random data
    status = RNGA_GetRandomData(RNG, data, sizeof(data));

    if(status == kStatus_Success)
    {
        /* Print data
        PRINTF("Random = 0x%X\r\n", i, data );
        PRINTF("Succeed.\r\n");
    }
    else
    {
        PRINTF("RNGA failed! (0x%x)\r\n", status);
    }

    /* Deinitialize RNGA
    RNGA_Deinit(RNG);
}

Note

It is important to note there is no known cryptographic proof showing this is a secure method of generating random data. In fact, there may be an attack against this random number generator if its output is used directly in a cryptographic application. The attack is based on the linearity of the internal shift registers. Therefore, it is highly recommended that this random data produced by this module be used as an entropy source to provide an input seed to a NIST-approved pseudo-random-number generator based on DES or SHA-1 and defined in NIST FIPS PUB 186-2 Appendix 3 and NIST FIPS PUB SP 800-90. The requirement is to maximize the entropy of this input seed. In order to do this, when data is extracted from RNGA as quickly as the hardware allows, there are about one or two bits of added entropy per 32-bit word. Any single bit of that word contains that entropy. Therefore, when used as an entropy source, a random number should be generated for each bit of entropy required, and the least significant bit (any bit would be equivalent) of each word retained. The remainder of each random number should then be discarded. Used this way, even with full knowledge of the internal state of RNGA and all prior random numbers, an attacker is not able to predict the values of the extracted bits. Other sources of entropy can be used along with RNGA to generate the seed to the pseudorandom algorithm. The more random sources combined to create the seed, the better. The following is a list of sources that can be easily combined with the output of this module:

• Current time using highest precision possible
• Real-time system inputs that can be characterized as "random"
• Other entropy supplied directly by the user

Files
file	fsl_rnga.h

Enumerations
enum	rnga_mode_t {   kRNGA_ModeNormal = 0U,   kRNGA_ModeSleep = 1U }
	RNGA working mode. More...

Functions
void	RNGA_Init (RNG_Type *base)
	Initializes the RNGA. More...
void	RNGA_Deinit (RNG_Type *base)
	Shuts down the RNGA. More...
status_t	RNGA_GetRandomData (RNG_Type *base, void *data, size_t data_size)
	Gets random data. More...
void	RNGA_Seed (RNG_Type *base, uint32_t seed)
	Feeds the RNGA module. More...
void	RNGA_SetMode (RNG_Type *base, rnga_mode_t mode)
	Sets the RNGA in normal mode or sleep mode. More...
rnga_mode_t	RNGA_GetMode (RNG_Type *base)
	Gets the RNGA working mode. More...

Driver version
#define	FSL_RNGA_DRIVER_VERSION   (MAKE_VERSION(2, 0, 1))
	RNGA driver version 2.0.1. More...

Macro Definition Documentation

#define FSL_RNGA_DRIVER_VERSION   (MAKE_VERSION(2, 0, 1))

Enumeration Type Documentation

enum rnga_mode_t

Enumerator
kRNGA_ModeNormal	Normal Mode. The ring-oscillator clocks are active; RNGA generates entropy (randomness) from the clocks and stores it in shift registers.
kRNGA_ModeSleep	Sleep Mode. The ring-oscillator clocks are inactive; RNGA does not generate entropy.

Function Documentation

void RNGA_Init

(

RNG_Type *

base

)

This function initializes the RNGA. When called, the RNGA entropy generation starts immediately.

Parameters

base	RNGA base address

void RNGA_Deinit

(

RNG_Type *

base

)

This function shuts down the RNGA.

Parameters

base	RNGA base address

status_t RNGA_GetRandomData	(	RNG_Type *	base,
		void *	data,
		size_t	data_size
	)

This function gets random data from the RNGA.

Parameters

base	RNGA base address
data	pointer to user buffer to be filled by random data
data_size	size of data in bytes

Returns

RNGA status

void RNGA_Seed	(	RNG_Type *	base,
		uint32_t	seed
	)

This function inputs an entropy value that the RNGA uses to seed its pseudo-random algorithm.

Parameters

base	RNGA base address
seed	input seed value

void RNGA_SetMode	(	RNG_Type *	base,
		rnga_mode_t	mode
	)

This function sets the RNGA in sleep mode or normal mode.

Parameters

base	RNGA base address
mode	normal mode or sleep mode

rnga_mode_t RNGA_GetMode

(

RNG_Type *

base

)

This function gets the RNGA working mode.

Parameters

base	RNGA base address

Returns

normal mode or sleep mode