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Title "RAND_set_rand_method 3" C RAND_set_rand_method, RAND_get_rand_method, RAND_SSLeay - select \s-1RAND\s0 method Header "SYNOPSIS" .Vb 1 #include <openssl/rand.h> .Ve .Vb 1 void RAND_set_rand_method(const RAND_METHOD *meth); .Ve .Vb 1 const RAND_METHOD *RAND_get_rand_method(void); .Ve .Vb 1 RAND_METHOD *RAND_SSLeay(void); .Ve Header "DESCRIPTION" A \s-1RAND_METHOD\s0 specifies the functions that OpenSSL uses for random number generation. By modifying the method, alternative implementations such as hardware RNGs may be used. \s-1IMPORTANT:\s0 See the \s-1NOTES\s0 section for important information about how these \s-1RAND\s0 \s-1API\s0 functions are affected by the use of \fB\s-1ENGINE\s0 \s-1API\s0 calls.

Initially, the default \s-1RAND_METHOD\s0 is the OpenSSL internal implementation, as returned by RAND_SSLeay().

\fIRAND_set_default_method() makes meth the method for \s-1PRNG\s0 use. \s-1NB\s0: This is true only whilst no \s-1ENGINE\s0 has been set as a default for \s-1RAND\s0, so this function is no longer recommended.

\fIRAND_get_default_method() returns a pointer to the current \s-1RAND_METHOD\s0. However, the meaningfulness of this result is dependant on whether the \s-1ENGINE\s0 \s-1API\s0 is being used, so this function is no longer recommended.

Header "THE RAND_METHOD STRUCTURE" .Vb 9 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; .Ve The components point to the implementation of RAND_seed(), \fIRAND_bytes(), RAND_cleanup(), RAND_add(), RAND_pseudo_rand() and RAND_status(). Each component may be \s-1NULL\s0 if the function is not implemented. Header "RETURN VALUES" \fIRAND_set_rand_method() returns no value. RAND_get_rand_method() and \fIRAND_SSLeay() return pointers to the respective methods. Header "NOTES" As of version 0.9.7, \s-1RAND_METHOD\s0 implementations are grouped together with other algorithmic APIs (eg. \s-1RSA_METHOD\s0, \s-1EVP_CIPHER\s0, etc) in \s-1ENGINE\s0 modules. If a default \s-1ENGINE\s0 is specified for \s-1RAND\s0 functionality using an \s-1ENGINE\s0 \s-1API\s0 function, that will override any \s-1RAND\s0 defaults set using the \s-1RAND\s0 \s-1API\s0 (ie. \fIRAND_set_rand_method()). For this reason, the \s-1ENGINE\s0 \s-1API\s0 is the recommended way to control default implementations for use in \s-1RAND\s0 and other cryptographic algorithms. Header "SEE ALSO" rand(3), engine(3) Header "HISTORY" \fIRAND_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 \s-1ENGINE\s0 pointer as its argument. As of version 0.9.7, that has been reverted as the \s-1ENGINE\s0 \s-1API\s0 transparently overrides \s-1RAND\s0 defaults if used, otherwise \s-1RAND\s0 \s-1API\s0 functions work as before. RAND_set_rand_engine() was also introduced in version 0.9.7.