DH_NEW_BY_NID(3ossl)

💖 DH_NEW_BY_NID 💖

okay bestie, we're doing a whole page from the OpenSSL manual set — this one is DH_new_by_nid(3ossl), and it's about named DH parameters. yes, Diffie-Hellman, we love her, we respect her, and honestly? she's lowkey deprecated now. let's get into it 🫶

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✨ NAME ✨

DH_new_by_nid, DH_get_nid — create or get DH named parameters 🌸

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✨ SYNOPSIS ✨

#include <openssl/dh.h>

okay so heads up: 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 — go peek at openssl_user_macros(7) for the deets 💅

DH *DH_new_by_nid(int nid);

int DH_get_nid(const DH *dh);

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✨ DESCRIPTION ✨

🦋 DH_new_by_nid()

she creates and returns a DH structure containing named parameters nid. that's it, that's the job 💖

currently nid must be one of these, no substitutions, no vibes-based guessing:

• NID_ffdhe2048
• NID_ffdhe3072
• NID_ffdhe4096
• NID_ffdhe6144
• NID_ffdhe8192
• NID_modp_1536
• NID_modp_2048
• NID_modp_3072
• NID_modp_4096
• NID_modp_6144
• NID_modp_8192

like, that's the whole guest list, bestie 🎀

🦋 DH_get_nid()

this one looks at the parameters sitting inside dh and is like "hmm, do I know you?" — she determines if they match any named safe prime group 🌈

she returns the NID corresponding to the matching parameters, or NID_undef if there's no match. simple as that ✨

🚨 and yes, this function is deprecated. saying it again so it sticks 💀

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✨ RETURN VALUES ✨

• DH_new_by_nid() returns a set of DH parameters, or NULL if an error occurred 😭
• DH_get_nid() returns the NID of the matching set of parameters for p and g and optionally q, otherwise it returns NID_undef if there is no match 🙈

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✨ HISTORY ✨

all of these functions were deprecated in OpenSSL 3.0. the way that the entire page is basically a farewell tour 😭💜

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✨ COPYRIGHT ✨

Copyright 2017-2020 The OpenSSL Project Authors. All Rights Reserved. 👑

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> 📜

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and that's the whole page, bestie!! this was DH_NEW_BY_NID(3ossl) from the OpenSSL docs — version 3.5.9, dated 2026-09-29 ✨ go forth and use named parameters responsibly, ily, mwah 💅💖🦋