RANDadd(3) OpenSSL RANDadd(3)

NAME
       RANDadd, RANDseed, RANDstatus, RANDevent, RANDscreen - add entropy
       to the PRNG

SYNOPSIS
        #include 

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

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

        int  RANDstatus(void);

        int  RANDevent(UINT iMsg, WPARAM wParam, LPARAM lParam);
        void RANDscreen(void);

DESCRIPTION
       RANDadd() mixes the nnuumm bytes at bbuuff into the PRNG state. Thus, if the
       data at bbuuff are unpredictable to an adversary, 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 eennttrrooppyy argument is (the
       lower bound of) an estimate of how much randomness is contained in bbuuff,
       measured in bytes. Details about sources of randomness and how to
       estimate their entropy can be found in the literature, e.g. RFC 1750.

       RANDadd() 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 randomness device is used to
       seed the PRNG transparently. However, on all other systems, the
       application is responsible for seeding the PRNG by calling RANDadd(),
       RANDegd(3) or RANDloadfile(3).

       RANDseed() is equivalent to RANDadd() when nnuumm ==== eennttrrooppyy.

       RANDevent() collects the entropy from Windows events such as mouse
       movements and other user interaction. It should be called with the
       iiMMssgg, wwPPaarraamm and llPPaarraamm arguments of all messages sent to the window
       procedure. It will estimate the entropy contained in the event message
       (if any), and add it to the PRNG. The program can then process the
       messages as usual.

       The RANDscreen() function is available for the convenience of Windows
       programmers. It adds the current contents of the screen to the PRNG.
       For applications that can catch Windows events, seeding the PRNG by
       calling RANDevent() is a significantly better source of randomness. It
       should be noted that both methods cannot be used on servers that run
       without user interaction.

RETURN VALUES
       RANDstatus() and RANDevent() return 1 if the PRNG has been seeded
       with enough data, 0 otherwise.

       The other functions do not return values.

SEE ALSO
       rand(3), RANDegd(3), RANDloadfile(3), RANDcleanup(3)

HISTORY       RANDseed() and RANDscreen() are available in all versions of SSLeay
       and OpenSSL. RANDadd() and RANDstatus() have been added in OpenSSL
       0.9.5, RANDevent() in OpenSSL 0.9.5a.



0.9.7l                            2000-03-22                       RANDadd(3)