D2I_DHPARAMS(3)

💅 D2I_DHPARAMS(3) — bestie edition 💅

ok so this one lives in the Library Functions Manual, and honestly? it's a lil niche but it slays at exactly one job and does it perfectly. grab a strawberry 🍓 and let's get into it.

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✨ NAME ✨

d2i_DHparams, i2d_DHparams — the PKCS#3 DH parameter functions, aka the duo that turns DH params into bytes and back again 🎀

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🌸 SYNOPSIS 🌸

bestie it's a library situation — you gotta pull in libcrypto and include the header first:

#include <openssl/dh.h>

then the two little icons themselves:

DH *
d2i_DHparams(DH **a, unsigned char **pp, long length);

int
i2d_DHparams(DH *a, unsigned char **pp);

like, look at them. so simple. so powerful. 😭

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🦋 DESCRIPTION 🦋

okay so here's the vibe: these two functions decode and encode PKCS#3 DH parameters, using the DHparameter structure described in PKCS#3. that's it, that's the whole personality. 👑

otherwise they behave in a way similar to d2i_X509(3) and i2d_X509(3) — so if you already know how those roll, you already know how these roll. iykyk. 💅

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💖 RETURN VALUES 💖

• d2i_DHparams() — returns a DH object 💫 … or NULL if an error occurs. and yes, always check for the NULL, bestie, do not skip the vibe check 🙈
• i2d_DHparams() — returns the number of bytes successfully encoded ✨ … or a value <= 0 if an error occurs. anything at or below zero is a red flag, no cap 💀

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🫶 SEE ALSO 🫶

go read these next, they're literally the main characters:

• d2i_X509(3)
• DH_new(3)

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🌈 HISTORY 🌈

d2i_DHparams() and i2d_DHparams() first appeared in SSLeay 0.5.1 — ancient era, truly the origin story — and have been available since OpenBSD 2.4. iconic longevity, honestly. 👑

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ngl these are lowkey the "small but mighty" functions of the libcrypto world and i'm obsessed. 🧚

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and that's the page, bestie — brought to you by the Debian crew, dated June 8, 2025, serving D2I_DHPARAMS(3) realness from start to finish. periodt. 💜🎀