RAND_SET_RAND_METHOD

Section: OpenSSL (3)
Updated: 2020-07-28
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NAME

RAND_set_rand_method, RAND_get_rand_method, RAND_OpenSSL - select RAND method

SYNOPSIS

 #include <openssl/rand.h>

 RAND_METHOD *RAND_OpenSSL(void);

 int RAND_set_rand_method(const RAND_METHOD *meth);

 const RAND_METHOD *RAND_get_rand_method(void);

DESCRIPTION

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().

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.

COPYRIGHT

Licensed under the OpenSSL license (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>.