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Editing: DH_set_default_method.3
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Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH "NAME" DH_set_default_method, DH_get_default_method, DH_set_method, DH_new_method, DH_OpenSSL \- select DH method .SH "SYNOPSIS" .IX Header "SYNOPSIS" .Vb 1 \& #include <openssl/dh.h> \& \& void DH_set_default_method(const DH_METHOD *meth); \& \& const DH_METHOD *DH_get_default_method(void); \& \& int DH_set_method(DH *dh, const DH_METHOD *meth); \& \& DH *DH_new_method(ENGINE *engine); \& \& const DH_METHOD *DH_OpenSSL(void); .Ve .SH "DESCRIPTION" .IX Header "DESCRIPTION" A \fB\s-1DH_METHOD\s0\fR specifies the functions that OpenSSL uses for Diffie-Hellman operations. By modifying the method, alternative implementations such as hardware accelerators may be used. \s-1IMPORTANT:\s0 See the \s-1NOTES\s0 section for important information about how these \s-1DH API\s0 functions are affected by the use of \fB\s-1ENGINE\s0\fR \s-1API\s0 calls. .PP Initially, the default \s-1DH_METHOD\s0 is the OpenSSL internal implementation, as returned by \fBDH_OpenSSL()\fR. .PP \&\fBDH_set_default_method()\fR makes \fBmeth\fR the default method for all \s-1DH\s0 structures created later. \&\fB\s-1NB\s0\fR: This is true only whilst no \s-1ENGINE\s0 has been set as a default for \s-1DH,\s0 so this function is no longer recommended. This function is not thread-safe and should not be called at the same time as other OpenSSL functions. .PP \&\fBDH_get_default_method()\fR returns a pointer to the current default \s-1DH_METHOD.\s0 However, the meaningfulness of this result is dependent on whether the \s-1ENGINE API\s0 is being used, so this function is no longer recommended. .PP \&\fBDH_set_method()\fR selects \fBmeth\fR to perform all operations using the key \fBdh\fR. This will replace the \s-1DH_METHOD\s0 used by the \s-1DH\s0 key and if the previous method was supplied by an \s-1ENGINE,\s0 the handle to that \s-1ENGINE\s0 will be released during the change. It is possible to have \s-1DH\s0 keys that only work with certain \s-1DH_METHOD\s0 implementations (e.g. from an \s-1ENGINE\s0 module that supports embedded hardware-protected keys), and in such cases attempting to change the \s-1DH_METHOD\s0 for the key can have unexpected results. .PP \&\fBDH_new_method()\fR allocates and initializes a \s-1DH\s0 structure so that \fBengine\fR will be used for the \s-1DH\s0 operations. If \fBengine\fR is \s-1NULL,\s0 the default \s-1ENGINE\s0 for \s-1DH\s0 operations is used, and if no default \s-1ENGINE\s0 is set, the \s-1DH_METHOD\s0 controlled by \&\fBDH_set_default_method()\fR is used. .PP A new \s-1DH_METHOD\s0 object may be constructed using \fBDH_meth_new()\fR (see \&\fBDH_meth_new\fR\|(3)). .SH "RETURN VALUES" .IX Header "RETURN VALUES" \&\fBDH_OpenSSL()\fR and \fBDH_get_default_method()\fR return pointers to the respective \&\fB\s-1DH_METHOD\s0\fRs. .PP \&\fBDH_set_default_method()\fR returns no value. .PP \&\fBDH_set_method()\fR returns nonzero if the provided \fBmeth\fR was successfully set as the method for \fBdh\fR (including unloading the \s-1ENGINE\s0 handle if the previous method was supplied by an \s-1ENGINE\s0). .PP \&\fBDH_new_method()\fR returns \s-1NULL\s0 and sets an error code that can be obtained by \&\fBERR_get_error\fR\|(3) if the allocation fails. Otherwise it returns a pointer to the newly allocated structure. .SH "SEE ALSO" .IX Header "SEE ALSO" \&\fBDH_new\fR\|(3), \fBDH_new\fR\|(3), \fBDH_meth_new\fR\|(3) .SH "COPYRIGHT" .IX Header "COPYRIGHT" Copyright 2000\-2020 The OpenSSL Project Authors. All Rights Reserved. .PP Licensed under the OpenSSL license (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at <https://www.openssl.org/source/license.html>.
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