DH_METH_NEW(3SSL)

📦

version 4.0.3 · 13 versions

💖 DH_METH_NEW — the OpenSSL 3SSL era, bestie 💖

okay so. welcome to the DH_METH_NEW(3SSL) page in the OpenSSL manual, bestie. this is the group chat where we build up custom DH methods, and ngl, it's a little bit of a legacy situation. grab a boba, sit down, and let's get into it 🧋✨

🌸 NAME 🌸

DH_meth_new, DH_meth_free, DH_meth_dup, DH_meth_get0_name, DH_meth_set1_name, DH_meth_get_flags, DH_meth_set_flags, DH_meth_get0_app_data, DH_meth_set0_app_data, DH_meth_get_generate_key, DH_meth_set_generate_key, DH_meth_get_compute_key, DH_meth_set_compute_key, DH_meth_get_bn_mod_exp, DH_meth_set_bn_mod_exp, DH_meth_get_init, DH_meth_set_init, DH_meth_get_finish, DH_meth_set_finish, DH_meth_get_generate_params, DH_meth_set_generate_params — literally just routines to build up DH methods 💅

✨ SYNOPSIS ✨

#include <openssl/dh.h>

so the tea is: the following functions have been deprecated since OpenSSL 3.0, and you can hide them entirely by defining OPENSSL_API_COMPAT with a suitable version value — see openssl_user_macros(7). yeah. that's the vibe. 🙈

DH_METHOD *DH_meth_new(const char *name, int flags);

void DH_meth_free(DH_METHOD *dhm);

DH_METHOD *DH_meth_dup(const DH_METHOD *dhm);

const char *DH_meth_get0_name(const DH_METHOD *dhm);
int DH_meth_set1_name(DH_METHOD *dhm, const char *name);

int DH_meth_get_flags(const DH_METHOD *dhm);
int DH_meth_set_flags(DH_METHOD *dhm, int flags);

void *DH_meth_get0_app_data(const DH_METHOD *dhm);
int DH_meth_set0_app_data(DH_METHOD *dhm, void *app_data);

int (*DH_meth_get_generate_key(const DH_METHOD *dhm))(DH *);
int DH_meth_set_generate_key(DH_METHOD *dhm, int (*generate_key)(DH *));

int (*DH_meth_get_compute_key(const DH_METHOD *dhm))
    (unsigned char *key, const BIGNUM *pub_key, DH *dh);
int DH_meth_set_compute_key(DH_METHOD *dhm,
    int (*compute_key)(unsigned char *key, const BIGNUM *pub_key, DH *dh));

int (*DH_meth_get_bn_mod_exp(const DH_METHOD *dhm))
    (const DH *dh, BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
     const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
int DH_meth_set_bn_mod_exp(DH_METHOD *dhm,
    int (*bn_mod_exp)(const DH *dh, BIGNUM *r, const BIGNUM *a,
                      const BIGNUM *p, const BIGNUM *m, BN_CTX *ctx,
                      BN_MONT_CTX *m_ctx));

int (*DH_meth_get_init(const DH_METHOD *dhm))(DH *);
int DH_meth_set_init(DH_METHOD *dhm, int (*init)(DH *));

int (*DH_meth_get_finish(const DH_METHOD *dhm))(DH *);
int DH_meth_set_finish(DH_METHOD *dhm, int (*finish)(DH *));

int (*DH_meth_get_generate_params(const DH_METHOD *dhm))
    (DH *, int, int, BN_GENCB *);
int DH_meth_set_generate_params(DH_METHOD *dhm,
    int (*generate_params)(DH *, int, int, BN_GENCB *));

🦋 DESCRIPTION 🦋

heads up bestie: all of the functions described on this page are deprecated. applications should instead use the provider APIs. no cap. that's the whole mood of this page. 😭

the DH_METHOD type is a structure used for the provision of custom DH implementations. it provides a set of functions that OpenSSL uses to implement the various DH capabilities. it's giving "bring your own math" energy. 🔥

here's the full rundown, one by one:

DH_meth_new() — creates a new DH_METHOD structure. you gotta give it a unique name and a set of flags. the name should be a NULL terminated string, which will be duplicated and stored in the DH_METHOD object — so it's the caller's responsibility to free the original string. the flags get used during the construction of a new DH object based on this DH_METHOD, and any new DH object will have those flags set by default. she's setting the tone for every DH that comes after her 👑
DH_meth_dup() — creates a duplicate copy of the DH_METHOD object passed as a parameter. this might be useful for creating a new DH_METHOD based on an existing one, but with some differences. remix era 🎀
DH_meth_free() — destroys a DH_METHOD structure and frees up any memory associated with it. if the argument is NULL, nothing is done. she said "no thoughts, head empty, we return" ✨
DH_meth_get0_name() — returns a pointer to the name of this DH_METHOD. this is a pointer to the internal name string, so it should not be freed by the caller. DH_meth_set1_name() sets the name of the DH_METHOD to name. the string is duplicated and the copy is stored in the DH_METHOD structure, so the caller remains responsible for freeing the memory associated with the name. shared custody, but you own the original 🫶
DH_meth_get_flags() — returns the current value of the flags associated with this DH_METHOD. DH_meth_set_flags() gives you the ability to set those flags. vibe check passed 💅
DH_meth_get0_app_data() and DH_meth_set0_app_data() — provide the ability to associate implementation specific data with the DH_METHOD. it is the application's responsibility to free this data before the DH_METHOD is freed via a call to DH_meth_free(). so like, clean up your own room bestie, nobody else is doing it 🧹
DH_meth_get_generate_key() and DH_meth_set_generate_key() — get and set the function used for generating a new DH key pair, respectively. this function will be called in response to the application calling DH_generate_key(). the parameter for the function has the same meaning as for DH_generate_key(). 🔑
DH_meth_get_compute_key() and DH_meth_set_compute_key() — get and set the function used for computing a new DH shared secret, respectively. this function will be called in response to the application calling DH_compute_key(). the parameters for the function have the same meaning as for DH_compute_key(). shared secrets, shared vibes 🤝
DH_meth_get_bn_mod_exp() and DH_meth_set_bn_mod_exp() — get and set the function used for computing the following value:

r = a ^ p mod m

this function will be called by the default OpenSSL function for DH_generate_key(). the result is stored in the r parameter. this function may be NULL unless you're using the default generate key function, in which case it must be present. so like, optional until it's literally not. iconic behavior of a required-optional field 💀

DH_meth_get_init() and DH_meth_set_init() — get and set the function used for creating a new DH instance, respectively. this function will be called in response to the application calling DH_new() (if the current default DH_METHOD is this one) or DH_new_method(). the DH_new() and DH_new_method() functions will allocate the memory for the new DH object, and a pointer to this newly allocated structure will be passed as a parameter to the function. this function may be NULL. it's giving main character energy, handling her own grand entrance 🌟
DH_meth_get_finish() and DH_meth_set_finish() — get and set the function used for destroying an instance of a DH object, respectively. this function will be called in response to the application calling DH_free(). a pointer to the DH to be destroyed is passed as a parameter. the destroy function should be used for DH implementation specific clean up. the memory for the DH itself should not be freed by this function. this function may be NULL. do your own dishes, not somebody else's 🍽️
DH_meth_get_generate_params() and DH_meth_set_generate_params() — get and set the function used for generating DH parameters, respectively. this function will be called in response to the application calling DH_generate_parameters_ex() (or DH_generate_parameters()). the parameters for the function have the same meaning as for DH_generate_parameters_ex(). this function may be NULL. parameters are the blueprint, and she's the architect 🏗️

💜 RETURN VALUES 💜

DH_meth_new() and DH_meth_dup() return the newly allocated DH_METHOD object, or NULL on failure. it's giving success or nothing, no in-between 🎭
DH_meth_get0_name() and DH_meth_get_flags() return the name and flags associated with the DH_METHOD, respectively.
all other DH_meth_get_*() functions return the appropriate function pointer that has been set in the DH_METHOD, or NULL if no such pointer has yet been set. empty slot, empty results, that's the rule 🌈
DH_meth_set1_name() and all DH_meth_set_*() functions return 1 on success or 0 on failure. binary queen 👑

(yes, DH_new(3) is listed twice and i'm NOT touching it — the original said it twice, so we said it twice. periodt. 💅)

📜 HISTORY 📜

so basically all of these functions were deprecated in OpenSSL 3.0.

the functions described here were added in OpenSSL 1.1.0. glow-up then glow-down, it's a whole arc 🦋

👑 COPYRIGHT 👑

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html>.

and that's the whole page bestie, we ate and left absolutely no crumbs 🍓✨ this was DH_meth_new(3SSL) from OpenSSL 4.0.3, stamped 2026-09-29. go forth, hug your provider APIs, and stay slaying 💖🎀🦋

📦 where this page comes from

ubuntu stonking: libssl-doc 4.0.3-1ubuntu1 · Apache-2.0
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash on 2026-11-03: a language model's rewrite of the original, under its terms