EVP_PKEY_COPY_PARAMETERS(3SSL)

✨ NAME ✨

EVP_PKEY_missing_parameters, EVP_PKEY_copy_parameters, EVP_PKEY_parameters_eq, EVP_PKEY_cmp_parameters, EVP_PKEY_eq, EVP_PKEY_cmp — public key parameter and comparison functions 💅

okay so this is the OpenSSL page for all the little pals that do public key parameter checkin' and key comparison. yes bestie, we're in the 3SSL section, get cozy 🫶

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🌸 SYNOPSIS 🌸

#include <openssl/evp.h>

int EVP_PKEY_missing_parameters(const EVP_PKEY *pkey);
int EVP_PKEY_copy_parameters(EVP_PKEY *to, const EVP_PKEY *from);

int EVP_PKEY_parameters_eq(const EVP_PKEY *a, const EVP_PKEY *b);
int EVP_PKEY_eq(const EVP_PKEY *a, const EVP_PKEY *b);

now heads up because the next two are giving retired icon energy — 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):

int EVP_PKEY_cmp_parameters(const EVP_PKEY *a, const EVP_PKEY *b);
int EVP_PKEY_cmp(const EVP_PKEY *a, const EVP_PKEY *b);

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💖 DESCRIPTION 💖

• EVP_PKEY_missing_parameters() — returns 1 if the public key parameters of pkey are missing, and 0 if they are present or the algorithm doesn't use parameters. like... it's literally just vibe-checking whether the params showed up or not 🕵️♀️
• EVP_PKEY_copy_parameters() — copies the parameters from key from to key to. An error is returned if the parameters are missing in from, or present in both from and to and they mismatch 👀. If the parameters in from and to are both present and match, this function has no effect — it just be like that, nothing to do, no notes.
• EVP_PKEY_parameters_eq() — checks the parameters of keys a and b for equality. are they the same babe or not 🔍
• EVP_PKEY_eq() — checks the keys a and b for equality, including their parameters if they are available. full glow-up comparison, not just the surface.

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📝 NOTES 📝

The main purpose of EVP_PKEY_missing_parameters() and EVP_PKEY_copy_parameters() is to handle public keys in certificates where the parameters are sometimes omitted from a public key if they are inherited from the CA that signed it. no cap, it's a real inheritance-situation thing 👑

The deprecated functions EVP_PKEY_cmp() and EVP_PKEY_cmp_parameters() differ in their return values compared to other _cmp() functions. they are aliases for EVP_PKEY_eq() and EVP_PKEY_parameters_eq(). so like, same girlies, different paperwork 💀

The function EVP_PKEY_cmp() previously only checked the key parameters (if there are any) and the public key, assuming that there always was a public key and that private key equality could be derived from that. Because it's no longer assumed that the private key in an EVP_PKEY(3) is always accompanied by a public key, the comparison can not rely on public key comparison alone. awkward!! it used to assume and now it cannot 😭

Instead, EVP_PKEY_eq() (and therefore also EVP_PKEY_cmp()) now compares:

1. the key parameters (if there are any)
2. the public keys or the private keys of the two EVP_PKEYs, depending on what they both contain.

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🎀 RETURN VALUES 🎀

• EVP_PKEY_missing_parameters() returns 1 if the public key parameters of pkey are missing and 0 if they are present or the algorithm doesn't use parameters.
• these functions — EVP_PKEY_copy_parameters() — returns 1 for success and 0 for failure. (yes the original really phrases it like that, i'm just the messenger bestie 💅)
• EVP_PKEY_cmp_parameters(), EVP_PKEY_parameters_eq(), EVP_PKEY_cmp() and EVP_PKEY_eq() return:
  • 1 if their inputs match ✅
  • 0 if they don't match ❌
  • -1 if the key types are different 🫠
  • -2 if the operation is not supported 🚫

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👀 SEE ALSO 👀

EVP_PKEY_CTX_new(3), EVP_PKEY_keygen(3)

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🌈 HISTORY 🌈

• The EVP_PKEY_cmp() and EVP_PKEY_cmp_parameters() functions were deprecated in OpenSSL 3.0.
• The EVP_PKEY_eq() and EVP_PKEY_parameters_eq() were added in OpenSSL 3.0 to replace EVP_PKEY_cmp() and EVP_PKEY_cmp_parameters(). out with the old, in with the iconic ✨

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📜 COPYRIGHT 📜

Copyright 2006-2021 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 EVP_PKEY_COPY_PARAMETERS(3SSL) from OpenSSL version 4.0.3, dated 2026-09-29 — slay, stay hydrated, go copy some parameters responsibly 💖✨