Random generation
Legacy HAL

Description

Functions that provide access to random numbers.

These functions may be hardware accelerated, though often are not.

See random.h for source code.

Functions

psa_status_t psa_generate_random (uint8_t *output, size_t output_size)
Generate random bytes.
psa_status_t psa_generate_key (const psa_key_attributes_t *attributes, mbedtls_svc_key_id_t *key)
Generate a key or key pair.
void halStackSeedRandom (uint32_t seed)
Seeds the halCommonGetRandom() pseudorandom number generator.
uint16_t halCommonGetRandom (void)
Runs a standard LFSR to generate pseudorandom numbers.

Function Documentation

◆ psa_generate_random()

psa_status_t psa_generate_random ( uint8_t * output,
size_t output_size
)

Generate random bytes.

Warning
This function can fail! Callers MUST check the return status and MUST NOT use the content of the output buffer if the return status is not PSA_SUCCESS .
Note
To generate a key, use psa_generate_key() instead.
Parameters
[out] output Output buffer for the generated data.
output_size Number of bytes to generate and output.
Return values
PSA_SUCCESS
PSA_ERROR_NOT_SUPPORTED
PSA_ERROR_INSUFFICIENT_ENTROPY
PSA_ERROR_INSUFFICIENT_MEMORY
PSA_ERROR_COMMUNICATION_FAILURE
PSA_ERROR_HARDWARE_FAILURE
PSA_ERROR_CORRUPTION_DETECTED
PSA_ERROR_BAD_STATE The library has not been previously initialized by psa_crypto_init() . It is implementation-dependent whether a failure to initialize results in this error code.

◆ psa_generate_key()

psa_status_t psa_generate_key ( const psa_key_attributes_t * attributes,
mbedtls_svc_key_id_t * key
)

Generate a key or key pair.

The key is generated randomly. Its location, usage policy, type and size are taken from attributes .

Implementations must reject an attempt to generate a key of size 0.

The following type-specific considerations apply:

  • For RSA keys ( PSA_KEY_TYPE_RSA_KEY_PAIR ), the public exponent is 65537. The modulus is a product of two probabilistic primes between 2^{n-1} and 2^n where n is the bit size specified in the attributes.
Parameters
[in] attributes The attributes for the new key.
[out] key On success, an identifier for the newly created key. For persistent keys, this is the key identifier defined in attributes . 0 on failure.
Return values
PSA_SUCCESS Success. If the key is persistent, the key material and the key's metadata have been saved to persistent storage.
PSA_ERROR_ALREADY_EXISTS This is an attempt to create a persistent key, and there is already a persistent key with the given identifier.
PSA_ERROR_NOT_SUPPORTED
PSA_ERROR_INVALID_ARGUMENT
PSA_ERROR_INSUFFICIENT_MEMORY
PSA_ERROR_INSUFFICIENT_ENTROPY
PSA_ERROR_COMMUNICATION_FAILURE
PSA_ERROR_HARDWARE_FAILURE
PSA_ERROR_CORRUPTION_DETECTED
PSA_ERROR_INSUFFICIENT_STORAGE
PSA_ERROR_DATA_INVALID
PSA_ERROR_DATA_CORRUPT
PSA_ERROR_STORAGE_FAILURE
PSA_ERROR_BAD_STATE The library has not been previously initialized by psa_crypto_init() . It is implementation-dependent whether a failure to initialize results in this error code.

◆ halStackSeedRandom()

void halStackSeedRandom ( uint32_t seed )

Seeds the halCommonGetRandom() pseudorandom number generator.

Called by the stack during initialization with a seed from the radio.

Parameters
seed A seed for the pseudorandom number generator.

◆ halCommonGetRandom()

uint16_t halCommonGetRandom ( void )

Runs a standard LFSR to generate pseudorandom numbers.

Called by the MAC in the stack to choose random backoff slots.

Complicated implementations may improve the MAC's ability to avoid collisions in large networks, but it is critical to implement this function to return quickly.