RAND_set_rand_method(3)

RAND_set_rand_method(3) | OpenSSL | RAND_set_rand_method(3)

# NAME

RAND_set_rand_method, RAND_get_rand_method, RAND_OpenSSL - select RAND method

# SYNOPSIS

     #include <openssl/rand.h>

The following functions have been deprecated since OpenSSL 3.0, and can be hidden entirely by defining OPENSSL_API_COMPAT with a suitable version value, see openssl_user_macros(7):

     RAND_METHOD *RAND_OpenSSL(void);
     int RAND_set_rand_method(const RAND_METHOD *meth);
     const RAND_METHOD *RAND_get_rand_method(void);

# DESCRIPTION

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);
     } RAND_METHOD;

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)

# HISTORY

All of these functions were deprecated in OpenSSL 3.0.

# COPYRIGHT

Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html>.

2025-07-01 | 3.5.1