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=head1 NAME

d2i_PKCS8PrivateKey_bio, d2i_PKCS8PrivateKey_fp,
i2d_PKCS8PrivateKey_bio, i2d_PKCS8PrivateKey_fp,
i2d_PKCS8PrivateKey_nid_bio, i2d_PKCS8PrivateKey_nid_fp - PKCS#8 format private key functions

=head1 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);

=head1 DESCRIPTION

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.

Other than the use of DER as opposed to PEM these functions are identical to the
corresponding B<PEM> function as described in L<PEM_read_PrivateKey(3)>.

=head1 NOTES

These functions are currently the only way to store encrypted private keys using DER format.

Currently all the functions use BIOs or FILE pointers, there are no functions
which support password-protection and work directly on memory: this can be
readily worked around by converting the buffers to memory BIOs, see
L<BIO_s_mem(3)> for details.
If password-protection is not required, the L<i2d_PKCS8PrivateKey(3)> function
encodes a private key to an unencrypted DER B<PKCS#8> form.

These functions make no assumption regarding the pass phrase received from the
password callback.
It will simply be treated as a byte sequence.

=head1 RETURN VALUES

d2i_PKCS8PrivateKey_bio() and d2i_PKCS8PrivateKey_fp() return a valid B<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.

=head1 SEE ALSO

L<i2d_PKCS8PrivateKey(3)>,
L<PEM_read_PrivateKey(3)>,
L<passphrase-encoding(7)>

=head1 HISTORY

L<i2d_PKCS8PrivateKey(3)> was added in OpenSSL 3.6.

=head1 COPYRIGHT

Copyright 2002-2025 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
L<https://www.openssl.org/source/license.html>.

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