ctr_drbg.h File Reference

This file contains definitions and functions for the CTR_DRBG pseudorandom generator. More...

#include "mbedtls/config.h"
#include "mbedtls/aes.h"

Go to the source code of this file.

Data Structures
struct	mbedtls_ctr_drbg_context
	The CTR_DRBG context structure. More...

Macros
#define	MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED   -0x0034
	The entropy source failed. More...
#define	MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG   -0x0036
	The requested random buffer length is too big. More...
#define	MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG   -0x0038
	The input (entropy + additional data) is too large. More...
#define	MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR   -0x003A
	Read or write error in file. More...
#define	MBEDTLS_CTR_DRBG_BLOCKSIZE   16
	The block size used by the cipher. More...
#define	MBEDTLS_CTR_DRBG_KEYSIZE   32
	The key size in bytes used by the cipher. More...
#define	MBEDTLS_CTR_DRBG_KEYBITS   ( MBEDTLS_CTR_DRBG_KEYSIZE * 8 )
	The key size for the DRBG operation, in bits. More...
#define	MBEDTLS_CTR_DRBG_SEEDLEN   ( MBEDTLS_CTR_DRBG_KEYSIZE + MBEDTLS_CTR_DRBG_BLOCKSIZE )
	The seed length, calculated as (counter + AES key). More...
#define	MBEDTLS_CTR_DRBG_PR_OFF   0
	Prediction resistance is disabled. More...
#define	MBEDTLS_CTR_DRBG_PR_ON   1
	Prediction resistance is enabled. More...
#define	MBEDTLS_CTR_DRBG_ENTROPY_NONCE_LEN   ( MBEDTLS_CTR_DRBG_ENTROPY_LEN + 1 ) / 2
	The default length of the nonce read from the entropy source. More...
SECTION: Module settings
The configuration options you can set for this module are in this section. Either change them in config.h or define them using the compiler command line.
#define	MBEDTLS_CTR_DRBG_ENTROPY_LEN   32
	The amount of entropy used per seed by default, in bytes. More...
#define	MBEDTLS_CTR_DRBG_RESEED_INTERVAL   10000
	The interval before reseed is performed by default. More...
#define	MBEDTLS_CTR_DRBG_MAX_INPUT   256
	The maximum number of additional input Bytes. More...
#define	MBEDTLS_CTR_DRBG_MAX_REQUEST   1024
	The maximum number of requested Bytes per call. More...
#define	MBEDTLS_CTR_DRBG_MAX_SEED_INPUT   384
	The maximum size of seed or reseed buffer in bytes. More...

Typedefs
typedef struct mbedtls_ctr_drbg_context	mbedtls_ctr_drbg_context
	The CTR_DRBG context structure. More...

Functions
void	mbedtls_ctr_drbg_init (mbedtls_ctr_drbg_context *ctx)
	This function initializes the CTR_DRBG context, and prepares it for mbedtls_ctr_drbg_seed() or mbedtls_ctr_drbg_free(). More...
int	mbedtls_ctr_drbg_seed (mbedtls_ctr_drbg_context *ctx, int(*f_entropy)(void *, unsigned char *, size_t), void *p_entropy, const unsigned char *custom, size_t len)
	This function seeds and sets up the CTR_DRBG entropy source for future reseeds. More...
void	mbedtls_ctr_drbg_free (mbedtls_ctr_drbg_context *ctx)
	This function resets CTR_DRBG context to the state immediately after initial call of mbedtls_ctr_drbg_init(). More...
void	mbedtls_ctr_drbg_set_prediction_resistance (mbedtls_ctr_drbg_context *ctx, int resistance)
	This function turns prediction resistance on or off. More...
void	mbedtls_ctr_drbg_set_entropy_len (mbedtls_ctr_drbg_context *ctx, size_t len)
	This function sets the amount of entropy grabbed on each seed or reseed. More...
int	mbedtls_ctr_drbg_set_nonce_len (mbedtls_ctr_drbg_context *ctx, size_t len)
	This function sets the amount of entropy grabbed as a nonce for the initial seeding. More...
void	mbedtls_ctr_drbg_set_reseed_interval (mbedtls_ctr_drbg_context *ctx, int interval)
	This function sets the reseed interval. More...
int	mbedtls_ctr_drbg_reseed (mbedtls_ctr_drbg_context *ctx, const unsigned char *additional, size_t len)
	This function reseeds the CTR_DRBG context, that is extracts data from the entropy source. More...
int	mbedtls_ctr_drbg_update_ret (mbedtls_ctr_drbg_context *ctx, const unsigned char *additional, size_t add_len)
	This function updates the state of the CTR_DRBG context. More...
int	mbedtls_ctr_drbg_random_with_add (void *p_rng, unsigned char *output, size_t output_len, const unsigned char *additional, size_t add_len)
	This function updates a CTR_DRBG instance with additional data and uses it to generate random data. More...
int	mbedtls_ctr_drbg_random (void *p_rng, unsigned char *output, size_t output_len)
	This function uses CTR_DRBG to generate random data. More...
void	mbedtls_ctr_drbg_update (mbedtls_ctr_drbg_context *ctx, const unsigned char *additional, size_t add_len)
	This function updates the state of the CTR_DRBG context. More...

Detailed Description

This file contains definitions and functions for the CTR_DRBG pseudorandom generator.

CTR_DRBG is a standardized way of building a PRNG from a block-cipher in counter mode operation, as defined in NIST SP 800-90A: Recommendation for Random Number Generation Using Deterministic Random Bit Generators.

The Mbed TLS implementation of CTR_DRBG uses AES-256 (default) or AES-128 (if MBEDTLS_CTR_DRBG_USE_128_BIT_KEY is enabled at compile time) as the underlying block cipher, with a derivation function.

The security strength as defined in NIST SP 800-90A is 128 bits when AES-128 is used (MBEDTLS_CTR_DRBG_USE_128_BIT_KEY enabled) and 256 bits otherwise, provided that MBEDTLS_CTR_DRBG_ENTROPY_LEN is kept at its default value (and not overridden in config.h) and that the DRBG instance is set up with default parameters. See the documentation of mbedtls_ctr_drbg_seed() for more information.

Definition in file ctr_drbg.h.