PKCS12_KEY_GEN_UTF8_EX(3ossl)

📦 version 3.5.0, in opensuse-leap 16.0

💅 PKCS12_KEY_GEN_UTF8_EX — the OpenSSL 3ossl manual, but make it make sense

okay so bestie, this is the 3ossl section of the OpenSSL manual, and today's main character is PKCS#12 password-based key derivation. no cap, it's lowkey iconic 🎀

✨ 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 — PKCS#12 Password based key derivation 🦋

✨ 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 according to PKCS#12 (RFC7292). you feed them a password pass of length passlen, a salt salt of length saltlen, an iteration count iter, and a digest algorithm md_type. then the ID byte id decides what the resulting key is actually for 👑

🎀 the id byte, aka the vibe check

  • ID=1 — the pseudorandom bits being produced are to be used as key material for performing encryption or decryption 🔥
  • ID=2 — the pseudorandom bits being produced are to be used as an IV (Initial Value) for encryption or decryption ✨
  • ID=3 — the pseudorandom bits being produced are to be used as an integrity key for MACing 💅

🧚 which password format, tho?

the intended format of the supplied password is determined by the method you chose, so pick correctly bestie:

  • 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.

🍓 the actual arguments

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(). 🫶

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. 🙈

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. ⭐

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. 💖

Functions ending in _ex() allow for a library context ctx and property query propq to be used to select algorithm implementations. 🦋

🌈 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.

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. literally security through slowing the haters down 💀

💜 RETURN VALUES 💜

Returns 1 on success or 0 on error. that's it, that's the whole vibe check.

👑 CONFORMING TO 👑

IETF RFC 7292 (https://tools.ietf.org/html/rfc7292)

🎀 SEE ALSO 🎀

PKCS12_create_ex(3), PKCS12_pbe_crypt_ex(3), passphrase-encoding(7)

⭐ HISTORY ⭐

PKCS12_key_gen_asc_ex(), PKCS12_key_gen_uni_ex() and PKCS12_key_gen_utf8_ex() were added in OpenSSL 3.0. the _ex girlies are the new gen, iykyk ✨

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 that's the whole page, no notes 💅 mwah! this one's sourced from OpenSSL 3.5.0, dated 2026-09-25, and the manual section is PKCS12_KEY_GEN_UTF8_EX(3ossl) — go derive some keys, bestie, you got this 🫶🎀

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