PKCS12_KEY_GEN_UTF8_EX(3ossl)

📦
version 3.5.9 · 8 versions
, in fedora 43, fedora 44

💖 PKCS12_KEY_GEN_UTF8_EX 💖

okay bestie, so this is a page from the OpenSSL manual, section 3ossl — it's the one about PKCS12_key_gen_asc, and her whole little family of sisters. it's giving "password-based key derivation, but make it PKCS#12" ✨

🌸 NAME 🌸

PKCS12_key_gen_asc, PKCS12_key_gen_asc_ex, PKCS12_key_gen_uni, PKCS12_key_gen_uni_ex, PKCS12_key_gen_utf8, PKCS12_key_gen_utf8_ex — literally PKCS#12 Password based key derivation, no cap 🎀

✨ SYNOPSIS ✨

#include <openssl/pkcs12.h>

int PKCS12_key_gen_asc(const char *pass, int passlen, unsigned char *salt,
                       int saltlen, int id, int iter, int n,
                       unsigned char *out, const EVP_MD *md_type);
int PKCS12_key_gen_asc_ex(const char *pass, int passlen, unsigned char *salt,
                          int saltlen, int id, int iter, int n,
                          unsigned char *out, const EVP_MD *md_type,
                          OSSL_LIB_CTX *ctx, const char *propq);
int PKCS12_key_gen_uni(unsigned char *pass, int passlen, unsigned char *salt,
                       int saltlen, int id, int iter, int n,
                       unsigned char *out, const EVP_MD *md_type);
int PKCS12_key_gen_uni_ex(unsigned char *pass, int passlen, unsigned char *salt,
                          int saltlen, int id, int iter, int n,
                          unsigned char *out, const EVP_MD *md_type,
                          OSSL_LIB_CTX *ctx, const char *propq);
int PKCS12_key_gen_utf8(const char *pass, int passlen, unsigned char *salt,
                        int saltlen, int id, int iter, int n,
                        unsigned char *out, const EVP_MD *md_type);
int PKCS12_key_gen_utf8_ex(const char *pass, int passlen, unsigned char *salt,
                           int saltlen, int id, int iter, int n,
                           unsigned char *out, const EVP_MD *md_type,
                           OSSL_LIB_CTX *ctx, const char *propq);

💅 DESCRIPTION 💅

so these methods do a key derivation per PKCS#12 (that's RFC7292, iykyk) and they take:

  • an input password pass, of length passlen
  • a salt salt, of length saltlen
  • an iteration count iter
  • a digest algorithm md_type

and the ID byte id decides what the resulting key is actually for, bestie:

  • If ID=1, then the pseudorandom bits being produced are to be used as key material for performing encryption or decryption. 🔐
  • If ID=2, then the pseudorandom bits being produced are to be used as an IV (Initial Value) for encryption or decryption.
  • If ID=3, then the pseudorandom bits being produced are to be used as an integrity key for MACing.

and the format of the password you hand over depends on which sister you picked, so listen up:

  • PKCS12_key_gen_asc() and PKCS12_key_gen_asc_ex() expect an ASCII-formatted password.
  • PKCS12_key_gen_uni() and PKCS12_key_gen_uni_ex() expect a Unicode-formatted password.
  • PKCS12_key_gen_utf8() and PKCS12_key_gen_utf8_ex() expect a UTF-8 encoded password.

now the deets on each param, one by one, because we do not skip 🫶

pass is the password used in the derivation of length passlen. pass is an optional parameter and can be NULL. If passlen is -1, then the function will calculate the length of pass using strlen(). iconic behaviour honestly.

salt is the salt used in the derivation of length saltlen. If the salt is NULL, then saltlen must be 0. The function will not attempt to calculate the length of the salt because it is not assumed to be NULL terminated. so don't come for her about it 💀

iter is the iteration count and its value should be greater than or equal to 1. RFC 2898 suggests an iteration count of at least 1000. Any iter less than 1 is treated as a single iteration. (yes, even 0. even -5. one iteration, periodt.)

digest is the message digest function used in the derivation.

The derived key will be written to out. The size of the out buffer is specified via n. so like, n bytes go in, n bytes come out, that's the vibe check ✅

and the plot twist: functions ending in _ex() allow for a library context ctx and property query propq to be used to select algorithm implementations. fancy!! 👑

🦋 NOTES 🦋

A typical application of this function is to derive keying material for an encryption algorithm from a password in the pass, a salt in salt, and an iteration count. that's the whole main character arc right there.

Increasing the iter parameter slows down the algorithm which makes it harder for an attacker to perform a brute force attack using a large number of candidate passwords. so like… crank it up, bestie, it's a security feature not a bug 🌈

🎀 RETURN VALUES 🎀

Returns 1 on success or 0 on error. that's it, that's the whole personality. binary queen 💅

⭐ CONFORMING TO ⭐

IETF RFC 7292 (<https://tools.ietf.org/html/rfc7292>) — she follows the rules, she just does it with flair ✨

🔥 SEE ALSO 🔥

go read those too, they're all in the same friend group 🫶

🌈 HISTORY 🌈

PKCS12_key_gen_asc_ex(), PKCS12_key_gen_uni_ex() and PKCS12_key_gen_utf8_ex() were added in OpenSSL 3.0. glow-up era fr fr.

Copyright 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>.

⚠️ okay so legally speaking: you may not use this file except in compliance with the License. the license is not optional, it's not a suggestion, it's the whole vibe. read it, bestie. 🙈

and that's a wrap!! 🎀 this was OpenSSL 3.5.9, dated 2026-09-29, filed under PKCS12_KEY_GEN_UTF8_EX(3ossl) — thanks for coming to my ted talk, stay hydrated, salt your passwords (literally, salt is a parameter), and may all your derivations return 1 💖✨🦋🍓

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