RANDsetrandmethod(3) OpenSSL RANDsetrandmethod(3)

NAME
       RANDsetrandmethod, RANDgetrandmethod, RANDSSLeay - select RAND
       method

SYNOPSIS
        #include 

        void RANDsetrandmethod(const RANDMETHOD *meth);

        const RANDMETHOD *RANDgetrandmethod(void);

        RANDMETHOD *RANDSSLeay(void);

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

       Initially, the default RANDMETHOD is the OpenSSL internal
       implementation, as returned by RANDSSLeay().

       RANDsetdefaultmethod() makes mmeetthh the method for PRNG use. NNBB: This
       is true only whilst no ENGINE has been set as a default for RAND, so
       this function is no longer recommended.

       RANDgetdefaultmethod() returns a pointer to the current RANDMETHOD.
       However, the meaningfulness of this result is dependant on whether the
       ENGINE API is being used, so this function is no longer recommended.

TTHHEE RRAANNDDMMEETTHHOODD SSTTRRUUCCTTUURREE
        typedef struct randmethst
        {
               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);
        } RANDMETHOD;

       The components point to the implementation of RANDseed(),
       RANDbytes(), RANDcleanup(), RANDadd(), RANDpseudorand() and
       RANDstatus().  Each component may be NULL if the function is not
       implemented.

RETURN VALUES
       RANDsetrandmethod() returns no value. RANDgetrandmethod() and
       RANDSSLeay() return pointers to the respective methods.

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

SEE ALSO
       rand(3), engine(3)

HISTORY       RANDsetrandmethod(), RANDgetrandmethod() and RANDSSLeay() are
       available in all versions of OpenSSL.

       In the engine version of version 0.9.6, RANDsetrandmethod() was
       altered to take an ENGINE pointer as its argument. As of version 0.9.7,
       that has been reverted as the ENGINE API transparently overrides RAND
       defaults if used, otherwise RAND API functions work as before.
       RANDsetrandengine() was also introduced in version 0.9.7.



0.9.7l                            2002-08-05           RANDsetrandmethod(3)