2000-01-23 04:05:23 +08:00
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=pod
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=head1 NAME
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2002-08-06 00:27:01 +08:00
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DH_set_default_method, DH_get_default_method,
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2000-10-27 05:07:28 +08:00
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DH_set_method, DH_new_method, DH_OpenSSL - select DH method
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2000-01-23 04:05:23 +08:00
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=head1 SYNOPSIS
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#include <openssl/dh.h>
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2002-10-29 12:34:43 +08:00
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#include <openssl/engine.h>
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2000-01-23 04:05:23 +08:00
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2002-08-06 00:27:01 +08:00
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void DH_set_default_method(const DH_METHOD *meth);
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2000-01-23 04:05:23 +08:00
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2002-08-06 00:27:01 +08:00
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const DH_METHOD *DH_get_default_method(void);
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2000-01-23 04:05:23 +08:00
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2002-08-06 00:27:01 +08:00
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int DH_set_method(DH *dh, const DH_METHOD *meth);
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2000-01-23 04:05:23 +08:00
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2002-10-29 12:34:43 +08:00
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DH *DH_new_method(ENGINE *engine);
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2000-01-23 04:05:23 +08:00
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2002-08-06 00:27:01 +08:00
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const DH_METHOD *DH_OpenSSL(void);
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2000-01-23 04:05:23 +08:00
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=head1 DESCRIPTION
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A B<DH_METHOD> specifies the functions that OpenSSL uses for Diffie-Hellman
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operations. By modifying the method, alternative implementations
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2002-08-06 00:27:01 +08:00
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such as hardware accelerators may be used. IMPORTANT: See the NOTES section for
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important information about how these DH API functions are affected by the use
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of B<ENGINE> API calls.
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Initially, the default DH_METHOD is the OpenSSL internal implementation, as
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returned by DH_OpenSSL().
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DH_set_default_method() makes B<meth> the default method for all DH
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structures created later. B<NB>: This is true only whilst no ENGINE has been set
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as a default for DH, so this function is no longer recommended.
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DH_get_default_method() returns a pointer to the current default DH_METHOD.
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2007-11-19 17:18:03 +08:00
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However, the meaningfulness of this result is dependent on whether the ENGINE
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2002-08-06 00:27:01 +08:00
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API is being used, so this function is no longer recommended.
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DH_set_method() selects B<meth> to perform all operations using the key B<dh>.
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This will replace the DH_METHOD used by the DH key and if the previous method
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was supplied by an ENGINE, the handle to that ENGINE will be released during the
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change. It is possible to have DH keys that only work with certain DH_METHOD
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implementations (eg. from an ENGINE module that supports embedded
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hardware-protected keys), and in such cases attempting to change the DH_METHOD
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for the key can have unexpected results.
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DH_new_method() allocates and initializes a DH structure so that B<engine> will
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be used for the DH operations. If B<engine> is NULL, the default ENGINE for DH
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operations is used, and if no default ENGINE is set, the DH_METHOD controlled by
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DH_set_default_method() is used.
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2000-01-23 04:05:23 +08:00
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=head1 THE DH_METHOD STRUCTURE
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typedef struct dh_meth_st
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{
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/* name of the implementation */
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const char *name;
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/* generate private and public DH values for key agreement */
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int (*generate_key)(DH *dh);
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/* compute shared secret */
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int (*compute_key)(unsigned char *key, BIGNUM *pub_key, DH *dh);
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2000-03-10 01:07:55 +08:00
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/* compute r = a ^ p mod m (May be NULL for some implementations) */
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2000-01-23 04:05:23 +08:00
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int (*bn_mod_exp)(DH *dh, BIGNUM *r, BIGNUM *a, const BIGNUM *p,
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const BIGNUM *m, BN_CTX *ctx,
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BN_MONT_CTX *m_ctx);
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/* called at DH_new */
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int (*init)(DH *dh);
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/* called at DH_free */
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int (*finish)(DH *dh);
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int flags;
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char *app_data; /* ?? */
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} DH_METHOD;
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=head1 RETURN VALUES
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2002-08-06 00:27:01 +08:00
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DH_OpenSSL() and DH_get_default_method() return pointers to the respective
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B<DH_METHOD>s.
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DH_set_default_method() returns no value.
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DH_set_method() returns non-zero if the provided B<meth> was successfully set as
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the method for B<dh> (including unloading the ENGINE handle if the previous
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method was supplied by an ENGINE).
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2000-01-23 04:05:23 +08:00
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2002-08-06 00:27:01 +08:00
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DH_new_method() returns NULL and sets an error code that can be obtained by
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2015-08-18 03:21:33 +08:00
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L<ERR_get_error(3)> if the allocation fails. Otherwise it
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2002-08-06 00:27:01 +08:00
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returns a pointer to the newly allocated structure.
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2000-01-23 04:05:23 +08:00
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=head1 SEE ALSO
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2015-08-18 03:21:33 +08:00
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L<dh(3)>, L<DH_new(3)>
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2000-01-23 04:05:23 +08:00
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=cut
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