RAND_set_rand_method.3ossl - Man Page

select RAND method


 #include <openssl/rand.h>

Deprecated since OpenSSL 3.0, can be hidden entirely by defining OPENSSL_API_COMPAT with a suitable version value, see openssl_user_macros(7):


 int RAND_set_rand_method(const RAND_METHOD *meth);

 const RAND_METHOD *RAND_get_rand_method(void);


All of the functions described on this page are deprecated. Applications should instead use RAND_set_DRBG_type(3), EVP_RAND(3) and EVP_RAND(7).

A RAND_METHOD specifies the functions that OpenSSL uses for random number generation.

RAND_OpenSSL() returns the default RAND_METHOD implementation by OpenSSL. This implementation ensures that the PRNG state is unique for each thread.

If an ENGINE is loaded that provides the RAND API, however, it will be used instead of the method returned by RAND_OpenSSL().  This is deprecated in OpenSSL 3.0.

RAND_set_rand_method() makes meth the method for PRNG use.  If an ENGINE was providing the method, it will be released first.

RAND_get_rand_method() returns a pointer to the current RAND_METHOD.

The Rand_method Structure

 typedef struct rand_meth_st {
     int (*seed)(const void *buf, int num);
     int (*bytes)(unsigned char *buf, int num);
     void (*cleanup)(void);
     int (*add)(const void *buf, int num, double entropy);
     int (*pseudorand)(unsigned char *buf, int num);
     int (*status)(void);

The fields point to functions that are used by, in order, RAND_seed(), RAND_bytes(), internal RAND cleanup, RAND_add(), RAND_pseudo_rand() and RAND_status(). Each pointer may be NULL if the function is not implemented.

Return Values

RAND_set_rand_method() returns 1 on success and 0 on failure. RAND_get_rand_method() and RAND_OpenSSL() return pointers to the respective methods.

See Also

EVP_RAND(3), RAND_set_DRBG_type(3), RAND_bytes(3), ENGINE_by_id(3), EVP_RAND(7), RAND(7)


All of these functions were deprecated in OpenSSL 3.0.

Referenced By

The man pages RAND_get_rand_method.3ossl(3) and RAND_OpenSSL.3ossl(3) are aliases of RAND_set_rand_method.3ossl(3).

2021-09-09 3.0.0 OpenSSL