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=head1 NAME

RAND_set_rand_method, RAND_get_rand_method, RAND_OpenSSL - select RAND method

=head1 SYNOPSIS

 #include <openssl/rand.h>

 RAND_METHOD *RAND_OpenSSL(void);

 int RAND_set_rand_method(const RAND_METHOD *meth);

 const RAND_METHOD *RAND_get_rand_method(void);

=head1 DESCRIPTION

A B<RAND_METHOD> specifies the functions that OpenSSL uses for random number

generation.

RAND_OpenSSL() returns the default B<RAND_METHOD> implementation by OpenSSL.

This implementation ensures that the PRNG state is unique for each thread.

If an B<ENGINE> is loaded that provides the RAND API, however, it will

be used instead of the method returned by RAND_OpenSSL().

RAND_set_rand_method() makes B<meth> the method for PRNG use.  If an

ENGINE was providing the method, it will be released first.

RAND_get_rand_method() returns a pointer to the current B<RAND_METHOD>.

=head1 THE RAND_METHOD STRUCTURE

 typedef struct rand_meth_st {

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

     int (*bytes)(unsigned char *buf, int num);

     void (*cleanup)(void);

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

     int (*pseudorand)(unsigned char *buf, int num);

     int (*status)(void);

 } RAND_METHOD;

The fields point to functions that are used by, in order,

RAND_seed(), RAND_bytes(), internal RAND cleanup, RAND_add(), RAND_pseudo_rand()

and RAND_status().

Each pointer may be NULL if the function is not implemented.

=head1 RETURN VALUES

RAND_set_rand_method() returns 1 on success and 0 on failure.

RAND_get_rand_method() and RAND_OpenSSL() return pointers to the respective

methods.

=head1 SEE ALSO

L<RAND_bytes(3)>,

L<ENGINE_by_id(3)>,

L<RAND(7)>

=head1 COPYRIGHT

Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (the "License").  You may not use

this file except in compliance with the License.  You can obtain a copy

in the file LICENSE in the source distribution or at

L<https://www.openssl.org/source/license.html>.

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