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DH_SET_METHOD(3) FreeBSD Library Functions Manual DH_SET_METHOD(3) NAME DH_set_default_method, DH_get_default_method, DH_set_method, DH_new_method, DH_OpenSSL - select DH method SYNOPSIS #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); DESCRIPTION A DH_METHOD object contains pointers to the functions used for Diffie- Hellman operations. By default, the internal implementation returned by DH_OpenSSL() is used. By selecting another method, alternative implementations such as hardware accelerators may be used. DH_set_default_method() selects meth as the default method for all DH structures created later. DH_get_default_method() returns a pointer to the current default method. DH_set_method() selects meth to perform all operations using the key dh. This replaces the DH_METHOD used by the dh key. It is possible to have DH keys that only work with certain DH_METHOD implementations, 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. The engine argument is ignored and the default method controlled by DH_set_default_method() is used. The DH_METHOD structure is defined as follows: 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; RETURN VALUES DH_OpenSSL() and DH_get_default_method() return pointers to the respective DH_METHOD. DH_set_method() returns 1 on success or 0 on failure. Currently, it cannot fail. DH_new_method() returns NULL and sets an error code that can be obtained by ERR_get_error(3) if the allocation fails. Otherwise it returns a pointer to the newly allocated structure. SEE ALSO DH_new(3) HISTORY DH_set_default_method(), DH_get_default_method(), DH_set_method(), DH_new_method() and DH_OpenSSL() first appeared in OpenSSL 0.9.5 and have been available since OpenBSD 2.7. FreeBSD 14.1-RELEASE-p8 November 19, 2023 FreeBSD 14.1-RELEASE-p8