D2I_PKCS8PRIVATEKEY_BIO(3ossl)

🌸 NAME 🌸

okay bestie, welcome to the OpenSSL manual page for D2I_PKCS8PRIVATEKEY_BIO(3ossl) — aka the PKCS#8 format private key functions. The whole squad is:

• d2i_PKCS8PrivateKey_bio
• d2i_PKCS8PrivateKey_fp
• i2d_PKCS8PrivateKey_bio
• i2d_PKCS8PrivateKey_fp
• i2d_PKCS8PrivateKey_nid_bio
• i2d_PKCS8PrivateKey_nid_fp

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✨ SYNOPSIS ✨

#include <openssl/pem.h>

EVP_PKEY *d2i_PKCS8PrivateKey_bio(BIO *bp, EVP_PKEY **x, pem_password_cb *cb, void *u);
EVP_PKEY *d2i_PKCS8PrivateKey_fp(FILE *fp, EVP_PKEY **x, pem_password_cb *cb, void *u);

int i2d_PKCS8PrivateKey_bio(BIO *bp, const EVP_PKEY *x, const EVP_CIPHER *enc,
                            char *kstr, int klen,
                            pem_password_cb *cb, void *u);

int i2d_PKCS8PrivateKey_fp(FILE *fp, const EVP_PKEY *x, const EVP_CIPHER *enc,
                           char *kstr, int klen,
                           pem_password_cb *cb, void *u);

int i2d_PKCS8PrivateKey_nid_bio(BIO *bp, const EVP_PKEY *x, int nid,
                                char *kstr, int klen,
                                pem_password_cb *cb, void *u);

int i2d_PKCS8PrivateKey_nid_fp(FILE *fp, const EVP_PKEY *x, int nid,
                               char *kstr, int klen,
                               pem_password_cb *cb, void *u);

💖 DESCRIPTION 💖

okay so the PKCS#8 functions encode and decode private keys in PKCS#8 format using both PKCS#5 v1.5 and PKCS#5 v2.0 password based encryption algorithms. literally carrying the encryption lore.

Other than the use of DER as opposed to PEM, these functions are identical to the corresponding PEM function as described in PEM_read_PrivateKey(3). twinsies, but make it DER 💅

🫶 NOTES 🫶

• rn these functions are the only way to store encrypted private keys using DER format. iconic and also just the facts.
• currently all the functions use BIOs or FILE pointers; there are no functions which work directly on memory. You can readily work this around by converting the buffers to memory BIOs — see BIO_s_mem(3) for details.
• these functions make no assumption regarding the pass phrase received from the password callback. It will simply be treated as a byte sequence. periodt.

🌈 RETURN VALUES 🌈

• d2i_PKCS8PrivateKey_bio() and d2i_PKCS8PrivateKey_fp() return a valid EVP_PKEY structure or NULL if an error occurred.
• i2d_PKCS8PrivateKey_bio(), i2d_PKCS8PrivateKey_fp(), i2d_PKCS8PrivateKey_nid_bio() and i2d_PKCS8PrivateKey_nid_fp() return 1 on success or 0 on error.

🦋 SEE ALSO 🦋

PEM_read_PrivateKey(3), passphrase-encoding(7)

👑 COPYRIGHT 👑

legal bestie moment, keep it exact:

Copyright 2002-2018 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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mwah 💋 — source/version: 3.5.0, date: 2026-09-25, page id: D2I_PKCS8PRIVATEKEY_BIO(3ossl).