1=pod 2 3=head1 NAME 4 5RAND_set_rand_method, RAND_get_rand_method, RAND_SSLeay - select RAND method 6 7=head1 SYNOPSIS 8 9 #include <openssl/rand.h> 10 11 void RAND_set_rand_method(const RAND_METHOD *meth); 12 13 const RAND_METHOD *RAND_get_rand_method(void); 14 15 RAND_METHOD *RAND_SSLeay(void); 16 17=head1 DESCRIPTION 18 19A B<RAND_METHOD> specifies the functions that OpenSSL uses for random number 20generation. By modifying the method, alternative implementations such as 21hardware RNGs may be used. IMPORTANT: See the NOTES section for important 22information about how these RAND API functions are affected by the use of 23B<ENGINE> API calls. 24 25Initially, the default RAND_METHOD is the OpenSSL internal implementation, as 26returned by RAND_SSLeay(). 27 28RAND_set_default_method() makes B<meth> the method for PRNG use. B<NB>: This is 29true only whilst no ENGINE has been set as a default for RAND, so this function 30is no longer recommended. 31 32RAND_get_default_method() returns a pointer to the current RAND_METHOD. 33However, the meaningfulness of this result is dependant on whether the ENGINE 34API is being used, so this function is no longer recommended. 35 36=head1 THE RAND_METHOD STRUCTURE 37 38 typedef struct rand_meth_st 39 { 40 void (*seed)(const void *buf, int num); 41 int (*bytes)(unsigned char *buf, int num); 42 void (*cleanup)(void); 43 void (*add)(const void *buf, int num, int entropy); 44 int (*pseudorand)(unsigned char *buf, int num); 45 int (*status)(void); 46 } RAND_METHOD; 47 48The components point to the implementation of RAND_seed(), 49RAND_bytes(), RAND_cleanup(), RAND_add(), RAND_pseudo_rand() 50and RAND_status(). 51Each component may be NULL if the function is not implemented. 52 53=head1 RETURN VALUES 54 55RAND_set_rand_method() returns no value. RAND_get_rand_method() and 56RAND_SSLeay() return pointers to the respective methods. 57 58=head1 NOTES 59 60As of version 0.9.7, RAND_METHOD implementations are grouped together with other 61algorithmic APIs (eg. RSA_METHOD, EVP_CIPHER, etc) in B<ENGINE> modules. If a 62default ENGINE is specified for RAND functionality using an ENGINE API function, 63that will override any RAND defaults set using the RAND API (ie. 64RAND_set_rand_method()). For this reason, the ENGINE API is the recommended way 65to control default implementations for use in RAND and other cryptographic 66algorithms. 67 68=head1 SEE ALSO 69 70L<rand(3)|rand(3)>, L<engine(3)|engine(3)> 71 72=head1 HISTORY 73 74RAND_set_rand_method(), RAND_get_rand_method() and RAND_SSLeay() are 75available in all versions of OpenSSL. 76 77In the engine version of version 0.9.6, RAND_set_rand_method() was altered to 78take an ENGINE pointer as its argument. As of version 0.9.7, that has been 79reverted as the ENGINE API transparently overrides RAND defaults if used, 80otherwise RAND API functions work as before. RAND_set_rand_engine() was also 81introduced in version 0.9.7. 82 83=cut 84