TRNG.h

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/*!****************************************************************************
 *  @file       TRNG.h
 *
 *  @brief      TRNG driver header
 *
 *  @anchor ti_drivers_TRNG_Overview
 *  # Overview #
 *  The True Random Number Generator (TRNG) module generates numbers of variable
 *  lengths from a source of entropy. The output is suitable for applications
 *  requiring cryptographically random numbers such as keying material for
 *  private or symmetric keys.
 *
 *  @anchor ti_drivers_TRNG_Usage
 *  # Usage #
 *
 *  ## Before starting a TRNG operation #
 *
 *  Before starting a TRNG operation, the application must do the following:
 *      - Call TRNG_init() to initialize the driver.
 *      - Call TRNG_Params_init() to initialize the TRNG_Params to default values.
 *      - Modify the TRNG_Params as desired.
 *      - Call TRNG_open() to open an instance of the driver.
 *      - Initialize a blank CryptoKey. These opaque datastructures are representations
 *        of keying material and its storage. Depending on how the keying material
 *        is stored (RAM or flash, key store, key blob), the CryptoKey must be
 *        initialized differently. The TRNG API can handle all types of CryptoKey.
 *        However, not all device-specific implementions support all types of CryptoKey.
 *        Devices without a key store will not support CryptoKeys with keying material
 *        stored in a key store for example.
 *        All devices support plaintext CryptoKeys.
 *
 *  ## TRNG operations #
 *
 *  TRNG_generateEntropy() provides the most basic functionality. Use it to
 *  generate random numbers of a specified width without further restrictions.
 *  An example use-case would be generating a symmetric key for AES encryption
 *  and / or authentication.
 *
 *  To generate an ECC private key, you should use rejection sampling to ensure
 *  that the keying material is in the interval [1, n - 1]. The ECDH public key
 *  genreation APIs will reject private keys that are outside of this interval.
 *  This information may be used to generate keying material until a suitable
 *  key is generated. For most curves, it is improbable to generate a random number
 *  outside of this interval because n is a large number close to the maximum
 *  number that would fit in the k-byte keying material array. An example
 *  of how to do this is given below.
 *
 *  ## After the TRNG operation completes #
 *
 *  After the TRNG operation completes, the application should either start another operation
 *  or close the driver by calling TRNG_close().
 *
 *  @anchor ti_drivers_TRNG_Synopsis
 *  ## Synopsis
 *  @anchor ti_drivers_TRNG_Synopsis_Code
 *  @code
 *  // Import TRNG Driver definitions
 *  #include <ti/drivers/TRNG.h>
 *  #include <ti/drivers/cryptoutils/cryptokey/CryptoKeyPlaintext.h>
 *
 *  // Define name for TRNG channel index
 *  #define TRNG_INSTANCE 0
 *
 *  #define KEY_LENGTH_BYTES 16
 *
 *  TRNG_init();
 *
 *  handle = TRNG_open(TRNG_INSTANCE, NULL);
 *
 *  CryptoKeyPlaintext_initBlankKey(&entropyKey, entropyBuffer, KEY_LENGTH_BYTES);
 *
 *  result = TRNG_generateEntropy(handle, &entropyKey);
 *
 *  TRNG_close(handle);
 *
 *  @endcode
 *
 *  @anchor ti_drivers_TRNG_Examples
 *  ## Examples
 *
 *  ### Generate symmetric encryption key #
 *  @code
 *
 *  #include <ti/drivers/TRNG.h>
 *  #include <ti/drivers/cryptoutils/cryptokey/CryptoKeyPlaintext.h>
 *
 *  #define KEY_LENGTH_BYTES 16
 *
 *  TRNG_Handle handle;
 *  int_fast16_t result;
 *
 *  CryptoKey entropyKey;
 *  uint8_t entropyBuffer[KEY_LENGTH_BYTES];
 *
 *  handle = TRNG_open(0, NULL);
 *
 *  if (!handle) {
 *      // Handle error
 *      while(1);
 *  }
 *
 *  CryptoKeyPlaintext_initBlankKey(&entropyKey, entropyBuffer, KEY_LENGTH_BYTES);
 *
 *  result = TRNG_generateEntropy(handle, &entropyKey);
 *
 *  if (result != TRNG_STATUS_SUCCESS) {
 *      // Handle error
 *      while(1);
 *  }
 *
 *  TRNG_close(handle);
 *
 *  @endcode
 *
 *  ### Generate ECC private and public key using rejection sampling #
 *  @code
 *
 *  #include <ti/drivers/TRNG.h>
 *  #include <ti/drivers/ECDH.h>
 *  #include <ti/drivers/cryptoutils/cryptokey/CryptoKeyPlaintext.h>
 *  #include <ti/drivers/cryptoutils/ecc/ECCParams.h>
 *
 *  TRNG_Handle trngHandle;
 *  ECDH_Handle ecdhHandle;
 *
 *  CryptoKey privateKey;
 *  CryptoKey publicKey;
 *
 *  int_fast16_t trngResult;
 *  int_fast16_t ecdhResult;
 *
 *  uint8_t privateKeyingMaterial[32];
 *  uint8_t publicKeyingMaterial[64];
 *
 *  ECDH_OperationGeneratePublicKey genPubKeyOperation;
 *
 *  trngHandle = TRNG_open(0, NULL);
 *  if (!trngHandle) {
 *      while(1);
 *  }
 *
 *  ecdhHandle = ECDH_open(0, NULL);
 *  if (!ecdhHandle) {
 *      while(1);
 *  }
 *
 *  // Repeatedly generate random numbers until they are in the range [1, n - 1].
 *  // Since the NIST-P256 order is so close to 2^256, the probability of needing
 *  // to generate more than one random number is incredibly low but not non-zero.
 *  do {
 *
 *      CryptoKeyPlaintext_initBlankKey(&privateKey, privateKeyingMaterial, ECCParams_NISTP256.length);
 *      CryptoKeyPlaintext_initBlankKey(&publicKey, publicKeyingMaterial, 2 * ECCParams_NISTP256.length);
 *
 *      trngResult = TRNG_generateEntropy(trngHandle, &privateKey);
 *
 *      if (trngResult != TRNG_STATUS_SUCCESS) {
 *          while(1);
 *      }
 *
 *      ECDH_OperationGeneratePublicKey_init(&genPubKeyOperation);
 *      genPubKeyOperation.curve = &ECCParams_NISTP256;
 *      genPubKeyOperation.myPrivateKey = &privateKey;
 *      genPubKeyOperation.myPublicKey = &publicKey;
 *
 *      ecdhResult = ECDH_generatePublicKey(ecdhHandle, &genPubKeyOperation);
 *
 *  } while(ecdhResult == ECDH_STATUS_PRIVATE_KEY_LARGER_EQUAL_ORDER || ecdhResult == ECDH_STATUS_PRIVATE_KEY_ZERO);
 *
 *  TRNG_close(trngHandle);
 *  ECDH_close(ecdhHandle);
 *
 *  @endcode
 */

#ifndef ti_drivers_TRNG__include
#define ti_drivers_TRNG__include

#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>

#include <ti/drivers/cryptoutils/cryptokey/CryptoKey.h>

#ifdef __cplusplus
extern "C" {
#endif

#define TRNG_STATUS_RESERVED        (-32)

#define TRNG_STATUS_SUCCESS         (0)

#define TRNG_STATUS_ERROR           (-1)

#define TRNG_STATUS_RESOURCE_UNAVAILABLE (-2)

typedef struct {
    void               *object;

    void         const *hwAttrs;
} TRNG_Config;

typedef TRNG_Config  *TRNG_Handle;

typedef enum {
    TRNG_RETURN_BEHAVIOR_CALLBACK = 1,    
    TRNG_RETURN_BEHAVIOR_BLOCKING = 2,    
    TRNG_RETURN_BEHAVIOR_POLLING  = 4,    
} TRNG_ReturnBehavior;

typedef void (*TRNG_CallbackFxn) (TRNG_Handle handle,
                                  int_fast16_t returnValue,
                                  CryptoKey *entropy);

typedef struct {
    TRNG_ReturnBehavior     returnBehavior;             
    TRNG_CallbackFxn        callbackFxn;                
    uint32_t                timeout;                    
    void                   *custom;                     
} TRNG_Params;

extern const TRNG_Params TRNG_defaultParams;

void TRNG_init(void);

void TRNG_Params_init(TRNG_Params *params);

TRNG_Handle TRNG_open(uint_least8_t index, TRNG_Params *params);

void TRNG_close(TRNG_Handle handle);

int_fast16_t TRNG_generateEntropy(TRNG_Handle handle, CryptoKey *entropy);

TRNG_Handle TRNG_construct(TRNG_Config *config, const TRNG_Params *params);


#ifdef __cplusplus
}
#endif

#endif /* ti_drivers_TRNG__include */