ctr_drbg.h File Reference

CTR_DRBG is based on AES-256, as defined in NIST SP 800-90A: Recommendation for Random Number Generation Using Deterministic Random Bit Generators. More...

`#include "aes.h"`
`#include "mbedtls/threading.h"`
Include dependency graph for ctr_drbg.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
#define | MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG -0x0036
#define | MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG -0x0038
#define | MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR -0x003A
#define | MBEDTLS_CTR_DRBG_BLOCKSIZE 16
#define | MBEDTLS_CTR_DRBG_KEYSIZE 32
#define | MBEDTLS_CTR_DRBG_KEYBITS ( MBEDTLS_CTR_DRBG_KEYSIZE * 8 )
#define | MBEDTLS_CTR_DRBG_SEEDLEN ( MBEDTLS_CTR_DRBG_KEYSIZE + MBEDTLS_CTR_DRBG_BLOCKSIZE )
#define | MBEDTLS_CTR_DRBG_PR_OFF 0
#define | MBEDTLS_CTR_DRBG_PR_ON 1
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 48
#define | MBEDTLS_CTR_DRBG_RESEED_INTERVAL 10000
#define | MBEDTLS_CTR_DRBG_MAX_INPUT 256
#define | MBEDTLS_CTR_DRBG_MAX_REQUEST 1024
#define | MBEDTLS_CTR_DRBG_MAX_SEED_INPUT 384

## 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 clears CTR_CRBG context data. More...
void | mbedtls_ctr_drbg_set_prediction_resistance (mbedtls_ctr_drbg_context *ctx, int resistance)
| This function turns prediction resistance on or off. The default value is 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. The default value is MBEDTLS_CTR_DRBG_ENTROPY_LEN. More...
void | mbedtls_ctr_drbg_set_reseed_interval (mbedtls_ctr_drbg_context *ctx, int interval)
| This function sets the reseed interval. The default value is MBEDTLS_CTR_DRBG_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...
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...
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...
int | mbedtls_ctr_drbg_write_seed_file (mbedtls_ctr_drbg_context *ctx, const char *path)
| This function writes a seed file. More...
int | mbedtls_ctr_drbg_update_seed_file (mbedtls_ctr_drbg_context *ctx, const char *path)
| This function reads and updates a seed file. The seed is added to this instance. More...
int | mbedtls_ctr_drbg_self_test (int verbose)
| The CTR_DRBG checkup routine. More...
int | mbedtls_ctr_drbg_seed_entropy_len (mbedtls_ctr_drbg_context *, int(*)(void *, unsigned char *, size_t), void *, const unsigned char *, size_t, size_t)

## Detailed Description

CTR_DRBG is based on AES-256, as defined in NIST SP 800-90A: Recommendation for Random Number Generation Using Deterministic Random Bit Generators.

Definition in file ctr_drbg.h.

## Macro Definition Documentation

## MBEDTLS_CTR_DRBG_BLOCKSIZE

#define MBEDTLS_CTR_DRBG_BLOCKSIZE 16

The block size used by the cipher.

Definition at line 42 of file ctr_drbg.h.

## MBEDTLS_CTR_DRBG_ENTROPY_LEN

#define MBEDTLS_CTR_DRBG_ENTROPY_LEN 48

The amount of entropy used per seed by default:

- 48 with SHA-512.
- 32 with SHA-256.

Definition at line 58 of file ctr_drbg.h.

## MBEDTLS_CTR_DRBG_KEYBITS

#define MBEDTLS_CTR_DRBG_KEYBITS ( MBEDTLS_CTR_DRBG_KEYSIZE * 8 )

The key size for the DRBG operation, in bits.

Definition at line 44 of file ctr_drbg.h.

## MBEDTLS_CTR_DRBG_KEYSIZE

#define MBEDTLS_CTR_DRBG_KEYSIZE 32

The key size used by the cipher.

Definition at line 43 of file ctr_drbg.h.

## MBEDTLS_CTR_DRBG_MAX_INPUT

#define MBEDTLS_CTR_DRBG_MAX_INPUT 256

The maximum number of additional input Bytes.

Definition at line 78 of file ctr_drbg.h.

## MBEDTLS_CTR_DRBG_MAX_REQUEST

#define MBEDTLS_CTR_DRBG_MAX_REQUEST 1024

The maximum number of requested Bytes per call.

Definition at line 83 of file ctr_drbg.h.

## MBEDTLS_CTR_DRBG_MAX_SEED_INPUT

#define MBEDTLS_CTR_DRBG_MAX_SEED_INPUT 384

The maximum size of seed or reseed buffer.

Definition at line 88 of file ctr_drbg.h.

## MBEDTLS_CTR_DRBG_PR_OFF

#define MBEDTLS_CTR_DRBG_PR_OFF 0

Prediction resistance is disabled.

Definition at line 94 of file ctr_drbg.h.

## MBEDTLS_CTR_DRBG_PR_ON

#define MBEDTLS_CTR_DRBG_PR_ON 1

Prediction resistance is enabled.

Definition at line 96 of file ctr_drbg.h.

## MBEDTLS_CTR_DRBG_RESEED_INTERVAL

#define MBEDTLS_CTR_DRBG_RESEED_INTERVAL 10000

The interval before reseed is performed by default.

Definition at line 73 of file ctr_drbg.h.

## MBEDTLS_CTR_DRBG_SEEDLEN

#define MBEDTLS_CTR_DRBG_SEEDLEN ( MBEDTLS_CTR_DRBG_KEYSIZE + MBEDTLS_CTR_DRBG_BLOCKSIZE )

The seed length, calculated as (counter + AES key).

Definition at line 45 of file ctr_drbg.h.

## MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED

#define MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED -0x0034

The entropy source failed.

Definition at line 37 of file ctr_drbg.h.

## MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR

#define MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR -0x003A

Read or write error in file.

Definition at line 40 of file ctr_drbg.h.

## MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG

#define MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG -0x0038

The input (entropy + additional data) is too large.

Definition at line 39 of file ctr_drbg.h.

## MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG

#define MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG -0x0036

The requested random buffer length is too big.

Definition at line 38 of file ctr_drbg.h.

## Function Documentation

## mbedtls_ctr_drbg_free()

void mbedtls_ctr_drbg_free | ( | mbedtls_ctr_drbg_context * | ctx | ) |

This function clears CTR_CRBG context data.

Parameters

  ctx | The CTR_DRBG context to clear.

## mbedtls_ctr_drbg_init()

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().

Parameters

  ctx | The CTR_DRBG context to initialize.

## mbedtls_ctr_drbg_random()

int mbedtls_ctr_drbg_random | ( | void * | p_rng,
|  | unsigned char * | output,
|  | size_t | output_len
| ) |  |

This function uses CTR_DRBG to generate random data.

Note
  The function automatically reseeds if the reseed counter is exceeded.

Parameters

  p_rng | The CTR_DRBG context. This must be a pointer to a mbedtls_ctr_drbg_context structure.
  output | The buffer to fill.
  output_len | The length of the buffer.

Returns
  `0` on success, or MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG on failure.

## mbedtls_ctr_drbg_random_with_add()

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.

Note
  The function automatically reseeds if the reseed counter is exceeded.

Parameters

  p_rng | The CTR_DRBG context. This must be a pointer to a mbedtls_ctr_drbg_context structure.
  output | The buffer to fill.
  output_len | The length of the buffer.
  additional | Additional data to update. Can be NULL.
  add_len | The length of the additional data.

Returns
  `0` on success, or MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG on failure.

## mbedtls_ctr_drbg_reseed()

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.

Parameters

  ctx | The CTR_DRBG context.
  additional | Additional data to add to the state. Can be NULL.
  len | The length of the additional data.

Returns
  `0` on success, or MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on failure.

## mbedtls_ctr_drbg_seed()

int mbedtls_ctr_drbg_seed | ( | mbedtls_ctr_drbg_context * | ctx,
|  | int(*)(void *, unsigned char *, size_t) | f_entropy,
|  | void * | p_entropy,
|  | const unsigned char * | custom,
|  | size_t | len
| ) |  |

This function seeds and sets up the CTR_DRBG entropy source for future reseeds.

Note
  Personalization data can be provided in addition to the more generic entropy source, to make this instantiation as unique as possible.

Parameters

  ctx | The CTR_DRBG context to seed.
  f_entropy | The entropy callback, taking as arguments the `p_entropy` context, the buffer to fill, and the length of the buffer.
  p_entropy | The entropy context.
  custom | Personalization data, that is device-specific identifiers. Can be NULL.
  len | The length of the personalization data.

Returns
  `0` on success, or MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on failure.

## mbedtls_ctr_drbg_seed_entropy_len()

int mbedtls_ctr_drbg_seed_entropy_len | ( | mbedtls_ctr_drbg_context * | ,
|  | int(*)(void *, unsigned char *, size_t) | ,
|  | void * | ,
|  | const unsigned char * | ,
|  | size_t | ,
|  | size_t |
| ) |  |

## mbedtls_ctr_drbg_self_test()

int mbedtls_ctr_drbg_self_test | ( | int | verbose | ) |

The CTR_DRBG checkup routine.

Returns
  `0` on success, or `1` on failure.

## mbedtls_ctr_drbg_set_entropy_len()

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. The default value is MBEDTLS_CTR_DRBG_ENTROPY_LEN.

Parameters

  ctx | The CTR_DRBG context.
  len | The amount of entropy to grab.

## mbedtls_ctr_drbg_set_prediction_resistance()

void mbedtls_ctr_drbg_set_prediction_resistance | ( | mbedtls_ctr_drbg_context * | ctx,
|  | int | resistance
| ) |  |

This function turns prediction resistance on or off. The default value is off.

Note
  If enabled, entropy is gathered at the beginning of every call to mbedtls_ctr_drbg_random_with_add(). Only use this if your entropy source has sufficient throughput.

Parameters

  ctx | The CTR_DRBG context.
  resistance | MBEDTLS_CTR_DRBG_PR_ON or MBEDTLS_CTR_DRBG_PR_OFF.

## mbedtls_ctr_drbg_set_reseed_interval()

void mbedtls_ctr_drbg_set_reseed_interval | ( | mbedtls_ctr_drbg_context * | ctx,
|  | int | interval
| ) |  |

This function sets the reseed interval. The default value is MBEDTLS_CTR_DRBG_RESEED_INTERVAL.

Parameters

  ctx | The CTR_DRBG context.
  interval | The reseed interval.

## mbedtls_ctr_drbg_update()

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.

Parameters

  ctx | The CTR_DRBG context.
  additional | The data to update the state with.
  add_len | Length of `additional` data.

Note
  If `add_len` is greater than MBEDTLS_CTR_DRBG_MAX_SEED_INPUT, only the first MBEDTLS_CTR_DRBG_MAX_SEED_INPUT Bytes are used. The remaining Bytes are silently discarded.

## mbedtls_ctr_drbg_update_seed_file()

int mbedtls_ctr_drbg_update_seed_file | ( | mbedtls_ctr_drbg_context * | ctx,
|  | const char * | path
| ) |  |

This function reads and updates a seed file. The seed is added to this instance.

Parameters

  ctx | The CTR_DRBG context.
  path | The name of the file.

Returns
  `0` on success, MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error, MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG on failure.

## mbedtls_ctr_drbg_write_seed_file()

int mbedtls_ctr_drbg_write_seed_file | ( | mbedtls_ctr_drbg_context * | ctx,
|  | const char * | path
| ) |  |

This function writes a seed file.

Parameters

  ctx | The CTR_DRBG context.
  path | The name of the file.

Returns
  `0` on success, MBEDTLS_ERR_CTR_DRBG_FILE_IO_ERROR on file error, or MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED on failure.