RAND_SSLeay (3)

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NAME

RAND_set_rand_method, RAND_get_rand_method, RAND_SSLeay - select RAND method

SYNOPSIS

 #include <openssl/rand.h>

 void RAND_set_rand_method(const RAND_METHOD *meth);

 const RAND_METHOD *RAND_get_rand_method(void);

 RAND_METHOD *RAND_SSLeay(void);

DESCRIPTION

A specifies the functions that OpenSSL uses for random number generation. By modifying the method, alternative implementations such as hardware RNGs may be used. See the section for important information about how these functions are affected by the use of calls.

Initially, the default

is the OpenSSL internal implementation, as returned by RAND_SSLeay().

RAND_set_default_method() makes meth the method for

use. : This is true only whilst no has been set as a default for so this function is no longer recommended.

RAND_get_default_method() returns a pointer to the current

However, the meaningfulness of this result is dependent on whether the is being used, so this function is no longer recommended.

THE RAND_METHOD STRUCTURE

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

The components point to the implementation of RAND_seed(), RAND_bytes(), RAND_cleanup(), RAND_add(), RAND_pseudo_rand() and RAND_status(). Each component may be

if the function is not implemented.

RETURN VALUES

RAND_set_rand_method() returns no value. RAND_get_rand_method() and RAND_SSLeay() return pointers to the respective methods.

NOTES

As of version 0.9.7, implementations are grouped together with other algorithmic APIs (eg. etc) in modules. If a default is specified for functionality using an function, that will override any defaults set using the (ie. RAND_set_rand_method()). For this reason, the is the recommended way to control default implementations for use in and other cryptographic algorithms.

SEE ALSO

rand(3), engine(3)

HISTORY

RAND_set_rand_method(), RAND_get_rand_method() and RAND_SSLeay() are available in all versions of OpenSSL.

In the engine version of version 0.9.6, RAND_set_rand_method() was altered to take an

pointer as its argument. As of version 0.9.7, that has been reverted as the transparently overrides defaults if used, otherwise functions work as before. RAND_set_rand_engine() was also introduced in version 0.9.7.