1=pod 2 3=head1 NAME 4 5DH_set_default_method, DH_get_default_method, 6DH_set_method, DH_new_method, DH_OpenSSL - select DH method 7 8=head1 SYNOPSIS 9 10 #include <openssl/dh.h> 11 12 void DH_set_default_method(const DH_METHOD *meth); 13 14 const DH_METHOD *DH_get_default_method(void); 15 16 int DH_set_method(DH *dh, const DH_METHOD *meth); 17 18 DH *DH_new_method(ENGINE *engine); 19 20 const DH_METHOD *DH_OpenSSL(void); 21 22=head1 DESCRIPTION 23 24A B<DH_METHOD> specifies the functions that OpenSSL uses for Diffie-Hellman 25operations. By modifying the method, alternative implementations 26such as hardware accelerators may be used. IMPORTANT: See the NOTES section for 27important information about how these DH API functions are affected by the use 28of B<ENGINE> API calls. 29 30Initially, the default DH_METHOD is the OpenSSL internal implementation, as 31returned by DH_OpenSSL(). 32 33DH_set_default_method() makes B<meth> the default method for all DH 34structures created later. 35B<NB>: This is true only whilst no ENGINE has been set 36as a default for DH, so this function is no longer recommended. 37This function is not thread-safe and should not be called at the same time 38as other OpenSSL functions. 39 40DH_get_default_method() returns a pointer to the current default DH_METHOD. 41However, the meaningfulness of this result is dependent on whether the ENGINE 42API is being used, so this function is no longer recommended. 43 44DH_set_method() selects B<meth> to perform all operations using the key B<dh>. 45This will replace the DH_METHOD used by the DH key and if the previous method 46was supplied by an ENGINE, the handle to that ENGINE will be released during the 47change. It is possible to have DH keys that only work with certain DH_METHOD 48implementations (eg. from an ENGINE module that supports embedded 49hardware-protected keys), and in such cases attempting to change the DH_METHOD 50for the key can have unexpected results. 51 52DH_new_method() allocates and initializes a DH structure so that B<engine> will 53be used for the DH operations. If B<engine> is NULL, the default ENGINE for DH 54operations is used, and if no default ENGINE is set, the DH_METHOD controlled by 55DH_set_default_method() is used. 56 57A new DH_METHOD object may be constructed using DH_meth_new() (see 58L<DH_meth_new(3)>). 59 60=head1 RETURN VALUES 61 62DH_OpenSSL() and DH_get_default_method() return pointers to the respective 63B<DH_METHOD>s. 64 65DH_set_default_method() returns no value. 66 67DH_set_method() returns non-zero if the provided B<meth> was successfully set as 68the method for B<dh> (including unloading the ENGINE handle if the previous 69method was supplied by an ENGINE). 70 71DH_new_method() returns NULL and sets an error code that can be obtained by 72L<ERR_get_error(3)> if the allocation fails. Otherwise it 73returns a pointer to the newly allocated structure. 74 75=head1 SEE ALSO 76 77L<DH_new(3)>, L<DH_new(3)>, L<DH_meth_new(3)> 78 79=head1 COPYRIGHT 80 81Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved. 82 83Licensed under the OpenSSL license (the "License"). You may not use 84this file except in compliance with the License. You can obtain a copy 85in the file LICENSE in the source distribution or at 86L<https://www.openssl.org/source/license.html>. 87 88=cut 89