You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
129 lines
4.6 KiB
129 lines
4.6 KiB
=pod
|
|
|
|
=head1 NAME
|
|
|
|
DH_set_default_method, DH_get_default_method,
|
|
DH_set_method, DH_new_method, DH_OpenSSL - select DH method
|
|
|
|
=head1 SYNOPSIS
|
|
|
|
#include <openssl/dh.h>
|
|
#include <openssl/engine.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);
|
|
|
|
=head1 DESCRIPTION
|
|
|
|
A B<DH_METHOD> specifies the functions that OpenSSL uses for Diffie-Hellman
|
|
operations. By modifying the method, alternative implementations
|
|
such as hardware accelerators may be used. IMPORTANT: See the NOTES section for
|
|
important information about how these DH API functions are affected by the use
|
|
of B<ENGINE> API calls.
|
|
|
|
Initially, the default DH_METHOD is the OpenSSL internal implementation, as
|
|
returned by DH_OpenSSL().
|
|
|
|
DH_set_default_method() makes B<meth> the default method for all DH
|
|
structures created later. B<NB>: This is true only whilst no ENGINE has been set
|
|
as a default for DH, so this function is no longer recommended.
|
|
|
|
DH_get_default_method() returns a pointer to the current default DH_METHOD.
|
|
However, the meaningfulness of this result is dependent on whether the ENGINE
|
|
API is being used, so this function is no longer recommended.
|
|
|
|
DH_set_method() selects B<meth> to perform all operations using the key B<dh>.
|
|
This will replace the DH_METHOD used by the DH key and if the previous method
|
|
was supplied by an ENGINE, the handle to that ENGINE will be released during the
|
|
change. It is possible to have DH keys that only work with certain DH_METHOD
|
|
implementations (eg. from an ENGINE module that supports embedded
|
|
hardware-protected keys), and in such cases attempting to change the DH_METHOD
|
|
for the key can have unexpected results.
|
|
|
|
DH_new_method() allocates and initializes a DH structure so that B<engine> will
|
|
be used for the DH operations. If B<engine> is NULL, the default ENGINE for DH
|
|
operations is used, and if no default ENGINE is set, the DH_METHOD controlled by
|
|
DH_set_default_method() is used.
|
|
|
|
=head1 THE DH_METHOD STRUCTURE
|
|
|
|
typedef struct dh_meth_st
|
|
{
|
|
/* name of the implementation */
|
|
const char *name;
|
|
|
|
/* generate private and public DH values for key agreement */
|
|
int (*generate_key)(DH *dh);
|
|
|
|
/* compute shared secret */
|
|
int (*compute_key)(unsigned char *key, BIGNUM *pub_key, DH *dh);
|
|
|
|
/* compute r = a ^ p mod m (May be NULL for some implementations) */
|
|
int (*bn_mod_exp)(DH *dh, BIGNUM *r, BIGNUM *a, const BIGNUM *p,
|
|
const BIGNUM *m, BN_CTX *ctx,
|
|
BN_MONT_CTX *m_ctx);
|
|
|
|
/* called at DH_new */
|
|
int (*init)(DH *dh);
|
|
|
|
/* called at DH_free */
|
|
int (*finish)(DH *dh);
|
|
|
|
int flags;
|
|
|
|
char *app_data; /* ?? */
|
|
|
|
} DH_METHOD;
|
|
|
|
=head1 RETURN VALUES
|
|
|
|
DH_OpenSSL() and DH_get_default_method() return pointers to the respective
|
|
B<DH_METHOD>s.
|
|
|
|
DH_set_default_method() returns no value.
|
|
|
|
DH_set_method() returns non-zero if the provided B<meth> was successfully set as
|
|
the method for B<dh> (including unloading the ENGINE handle if the previous
|
|
method was supplied by an ENGINE).
|
|
|
|
DH_new_method() returns NULL and sets an error code that can be obtained by
|
|
L<ERR_get_error(3)|ERR_get_error(3)> if the allocation fails. Otherwise it
|
|
returns a pointer to the newly allocated structure.
|
|
|
|
=head1 NOTES
|
|
|
|
As of version 0.9.7, DH_METHOD implementations are grouped together with other
|
|
algorithmic APIs (eg. RSA_METHOD, EVP_CIPHER, etc) in B<ENGINE> modules. If a
|
|
default ENGINE is specified for DH functionality using an ENGINE API function,
|
|
that will override any DH defaults set using the DH API (ie.
|
|
DH_set_default_method()). For this reason, the ENGINE API is the recommended way
|
|
to control default implementations for use in DH and other cryptographic
|
|
algorithms.
|
|
|
|
=head1 SEE ALSO
|
|
|
|
L<dh(3)|dh(3)>, L<DH_new(3)|DH_new(3)>
|
|
|
|
=head1 HISTORY
|
|
|
|
DH_set_default_method(), DH_get_default_method(), DH_set_method(),
|
|
DH_new_method() and DH_OpenSSL() were added in OpenSSL 0.9.4.
|
|
|
|
DH_set_default_openssl_method() and DH_get_default_openssl_method() replaced
|
|
DH_set_default_method() and DH_get_default_method() respectively, and
|
|
DH_set_method() and DH_new_method() were altered to use B<ENGINE>s rather than
|
|
B<DH_METHOD>s during development of the engine version of OpenSSL 0.9.6. For
|
|
0.9.7, the handling of defaults in the ENGINE API was restructured so that this
|
|
change was reversed, and behaviour of the other functions resembled more closely
|
|
the previous behaviour. The behaviour of defaults in the ENGINE API now
|
|
transparently overrides the behaviour of defaults in the DH API without
|
|
requiring changing these function prototypes.
|
|
|
|
=cut
|
|
|