=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 void DH_set_default_method(DH_METHOD *meth); DH_METHOD *DH_get_default_method(void); DH_METHOD *DH_set_method(DH *dh, DH_METHOD *meth); DH *DH_new_method(DH_METHOD *meth); DH_METHOD *DH_OpenSSL(void); =head1 DESCRIPTION A B specifies the functions that OpenSSL uses for Diffie-Hellman operations. By modifying the method, alternative implementations such as hardware accelerators may be used. Initially, the default is to use the OpenSSL internal implementation. DH_OpenSSL() returns a pointer to that method. DH_set_default_method() makes B the default method for all B structures created later. DH_get_default_method() returns a pointer to the current default method. DH_set_method() selects B for all operations using the structure B. DH_new_method() allocates and initializes a B structure so that B will be used for the DH operations. If B is B, the 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 Bs. DH_set_default_method() returns no value. DH_set_method() returns a pointer to the B previously associated with B. DH_new_method() returns B and sets an error code that can be obtained by L if the allocation fails. Otherwise it returns a pointer to the newly allocated structure. =head1 SEE ALSO L, L =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. =cut