RAND_add(3) - NetBSD Manual Pages

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RAND_add(3)                  OpenSSL                  RAND_add(3)



NAME

       RAND_add, RAND_seed, RAND_status, RAND_event, RAND_screen
       - add entropy to the PRNG


LIBRARY

       libcrypto, -lcrypto


SYNOPSIS

        #include <openssl/rand.h>

        void RAND_seed(const void *buf, int num);

        void RAND_add(const void *buf, int num, double entropy);

        int  RAND_status(void);

        int  RAND_event(UINT iMsg, WPARAM wParam, LPARAM lParam);
        void RAND_screen(void);



DESCRIPTION

       RAND_add() mixes the num bytes at buf into the PRNG state.
       Thus, if the data at buf are unpredictable to an adver-
       sary, this increases the uncertainty about the state and
       makes the PRNG output less predictable. Suitable input
       comes from user interaction (random key presses, mouse
       movements) and certain hardware events. The entropy argu-
       ment is (the lower bound of) an estimate of how much ran-
       domness is contained in buf, measured in bytes. Details
       about sources of randomness and how to estimate their
       entropy can be found in the literature, e.g. RFC 1750.

       RAND_add() may be called with sensitive data such as user
       entered passwords. The seed values cannot be recovered
       from the PRNG output.

       OpenSSL makes sure that the PRNG state is unique for each
       thread. On systems that provide `/dev/urandom', the ran-
       domness device is used to seed the PRNG transparently.
       However, on all other systems, the application is respon-
       sible for seeding the PRNG by calling RAND_add(),
       RAND_egd(3) or RAND_load_file(3).

       RAND_seed() is equivalent to RAND_add() when num ==
       entropy.

       RAND_event() collects the entropy from Windows events such
       as mouse movements and other user interaction. It should
       be called with the iMsg, wParam and lParam arguments of
       all messages sent to the window procedure. It will esti-
       mate the entropy contained in the event message (if any),
       and add it to the PRNG. The program can then process the
       messages as usual.




2000-07-22                    0.9.6g                            1





RAND_add(3)                  OpenSSL                  RAND_add(3)


       The RAND_screen() function is available for the conve-
       nience of Windows programmers. It adds the current con-
       tents of the screen to the PRNG.  For applications that
       can catch Windows events, seeding the PRNG by calling
       RAND_event() is a significantly better source of random-
       ness. It should be noted that both methods cannot be used
       on servers that run without user interaction.


RETURN VALUES

       RAND_status() and RAND_event() return 1 if the PRNG has
       been seeded with enough data, 0 otherwise.

       The other functions do not return values.


SEE ALSO

       openssl_rand(3), RAND_egd(3), RAND_load_file(3),
       RAND_cleanup(3)


HISTORY

       RAND_seed() and RAND_screen() are available in all ver-
       sions of SSLeay and OpenSSL. RAND_add() and RAND_status()
       have been added in OpenSSL 0.9.5, RAND_event() in OpenSSL
       0.9.5a.


































2000-07-22                    0.9.6g                            2