=pod
{- OpenSSL::safe::output_do_not_edit_headers(); -}

=head1 NAME

openssl-pkcs8 - PKCS#8 format private key conversion command

=head1 SYNOPSIS

B<openssl> B<pkcs8>
[B<-help>]
[B<-topk8>]
[B<-inform> B<DER>|B<PEM>]
[B<-outform> B<DER>|B<PEM>]
[B<-in> I<filename>]
[B<-passin> I<arg>]
[B<-out> I<filename>]
[B<-passout> I<arg>]
[B<-iter> I<count>]
[B<-noiter>]
[B<-nocrypt>]
[B<-traditional>]
[B<-v2> I<alg>]
[B<-v2prf> I<alg>]
[B<-v1> I<alg>]
[B<-scrypt>]
[B<-scrypt_N> I<N>]
[B<-scrypt_r> I<r>]
[B<-scrypt_p> I<p>]
{- $OpenSSL::safe::opt_r_synopsis -}
{- $OpenSSL::safe::opt_engine_synopsis -}{- $OpenSSL::safe::opt_provider_synopsis -}

=head1 DESCRIPTION

This command processes private keys in PKCS#8 format. It can handle
both unencrypted PKCS#8 PrivateKeyInfo format and EncryptedPrivateKeyInfo
format with a variety of PKCS#5 (v1.5 and v2.0) and PKCS#12 algorithms.

=head1 OPTIONS

=over 4

=item B<-help>

Print out a usage message.

=item B<-topk8>

Normally a PKCS#8 private key is expected on input and a private key will be
written to the output file. With the B<-topk8> option the situation is
reversed: it reads a private key and writes a PKCS#8 format key.

=item B<-inform> B<DER>|B<PEM>, B<-outform> B<DER>|B<PEM>

The input and formats; the default is B<PEM>.
See L<openssl-format-options(1)> for details.

If a key is being converted from PKCS#8 form (i.e. the B<-topk8> option is
not used) then the input file must be in PKCS#8 format. An encrypted
key is expected unless B<-nocrypt> is included.

If B<-topk8> is not used and B<PEM> mode is set the output file will be an
unencrypted private key in PKCS#8 format. If the B<-traditional> option is
used then a traditional format private key is written instead.

If B<-topk8> is not used and B<DER> mode is set the output file will be an
unencrypted private key in traditional DER format.

If B<-topk8> is used then any supported private key can be used for the input
file in a format specified by B<-inform>. The output file will be encrypted
PKCS#8 format using the specified encryption parameters unless B<-nocrypt>
is included.

=item B<-traditional>

When this option is present and B<-topk8> is not, a traditional format private
key is written.

=item B<-in> I<filename>

This specifies the input filename to read a key from or standard input if this
option is not specified. If the key is encrypted a pass phrase will be
prompted for.

=item B<-passin> I<arg>, B<-passout> I<arg>

The password source for the input and output file.
For more information about the format of B<arg>
see L<openssl-passphrase-options(1)>.

=item B<-out> I<filename>

This specifies the output filename to write a key to or standard output by
default. If any encryption options are set then a pass phrase will be
prompted for. The output filename should B<not> be the same as the input
filename.

=item B<-iter> I<count>

When creating new PKCS#8 containers, use a given number of iterations on
the password in deriving the encryption key for the PKCS#8 output.
High values increase the time required to brute-force a PKCS#8 container.

=item B<-noiter>

When creating new PKCS#8 containers, use 1 as iteration count.

=item B<-nocrypt>

PKCS#8 keys generated or input are normally PKCS#8 EncryptedPrivateKeyInfo
structures using an appropriate password based encryption algorithm. With
this option an unencrypted PrivateKeyInfo structure is expected or output.
This option does not encrypt private keys at all and should only be used
when absolutely necessary. Certain software such as some versions of Java
code signing software used unencrypted private keys.

=item B<-v2> I<alg>

This option sets the PKCS#5 v2.0 algorithm.

The I<alg> argument is the encryption algorithm to use, valid values include
B<aes128>, B<aes256> and B<des3>. If this option isn't specified then B<aes256>
is used.

=item B<-v2prf> I<alg>

This option sets the PRF algorithm to use with PKCS#5 v2.0. A typical value
value would be B<hmacWithSHA256>. If this option isn't set then the default
for the cipher is used or B<hmacWithSHA256> if there is no default.

Some implementations may not support custom PRF algorithms and may require
the B<hmacWithSHA1> option to work.

=item B<-v1> I<alg>

This option indicates a PKCS#5 v1.5 or PKCS#12 algorithm should be used.  Some
older implementations may not support PKCS#5 v2.0 and may require this option.
If not specified PKCS#5 v2.0 form is used.

=item B<-scrypt>

Uses the B<scrypt> algorithm for private key encryption using default
parameters: currently N=16384, r=8 and p=1 and AES in CBC mode with a 256 bit
key. These parameters can be modified using the B<-scrypt_N>, B<-scrypt_r>,
B<-scrypt_p> and B<-v2> options.

=item B<-scrypt_N> I<N>, B<-scrypt_r> I<r>, B<-scrypt_p> I<p>

Sets the scrypt I<N>, I<r> or I<p> parameters.

{- $OpenSSL::safe::opt_r_item -}

{- $OpenSSL::safe::opt_engine_item -}

{- $OpenSSL::safe::opt_provider_item -}

=back

=head1 NOTES

By default, when converting a key to PKCS#8 format, PKCS#5 v2.0 using 256 bit
AES with HMAC and SHA256 is used.

Some older implementations do not support PKCS#5 v2.0 format and require
the older PKCS#5 v1.5 form instead, possibly also requiring insecure weak
encryption algorithms such as 56 bit DES.

Private keys encrypted using PKCS#5 v2.0 algorithms and high iteration
counts are more secure that those encrypted using the traditional
SSLeay compatible formats. So if additional security is considered
important the keys should be converted.

It is possible to write out DER encoded encrypted private keys in
PKCS#8 format because the encryption details are included at an ASN1
level whereas the traditional format includes them at a PEM level.

=head1 PKCS#5 V1.5 AND PKCS#12 ALGORITHMS

Various algorithms can be used with the B<-v1> command line option,
including PKCS#5 v1.5 and PKCS#12. These are described in more detail
below.

=over 4

=item B<PBE-MD2-DES PBE-MD5-DES>

These algorithms were included in the original PKCS#5 v1.5 specification.
They only offer 56 bits of protection since they both use DES.

=item B<PBE-SHA1-RC2-64>, B<PBE-MD2-RC2-64>, B<PBE-MD5-RC2-64>, B<PBE-SHA1-DES>

These algorithms are not mentioned in the original PKCS#5 v1.5 specification
but they use the same key derivation algorithm and are supported by some
software. They are mentioned in PKCS#5 v2.0. They use either 64 bit RC2 or
56 bit DES.

=item B<PBE-SHA1-RC4-128>, B<PBE-SHA1-RC4-40>, B<PBE-SHA1-3DES>, B<PBE-SHA1-2DES>, B<PBE-SHA1-RC2-128>, B<PBE-SHA1-RC2-40>

These algorithms use the PKCS#12 password based encryption algorithm and
allow strong encryption algorithms like triple DES or 128 bit RC2 to be used.

=back

=head1 EXAMPLES

Convert a private key to PKCS#8 format using default parameters (AES with
256 bit key and B<hmacWithSHA256>):

 openssl pkcs8 -in key.pem -topk8 -out enckey.pem

Convert a private key to PKCS#8 unencrypted format:

 openssl pkcs8 -in key.pem -topk8 -nocrypt -out enckey.pem

Convert a private key to PKCS#5 v2.0 format using triple DES:

 openssl pkcs8 -in key.pem -topk8 -v2 des3 -out enckey.pem

Convert a private key to PKCS#5 v2.0 format using AES with 256 bits in CBC
mode and B<hmacWithSHA512> PRF:

 openssl pkcs8 -in key.pem -topk8 -v2 aes-256-cbc -v2prf hmacWithSHA512 -out enckey.pem

Convert a private key to PKCS#8 using a PKCS#5 1.5 compatible algorithm
(DES):

 openssl pkcs8 -in key.pem -topk8 -v1 PBE-MD5-DES -out enckey.pem

Convert a private key to PKCS#8 using a PKCS#12 compatible algorithm
(3DES):

 openssl pkcs8 -in key.pem -topk8 -out enckey.pem -v1 PBE-SHA1-3DES

Read a DER unencrypted PKCS#8 format private key:

 openssl pkcs8 -inform DER -nocrypt -in key.der -out key.pem

Convert a private key from any PKCS#8 encrypted format to traditional format:

 openssl pkcs8 -in pk8.pem -traditional -out key.pem

Convert a private key to PKCS#8 format, encrypting with AES-256 and with
one million iterations of the password:

 openssl pkcs8 -in key.pem -topk8 -v2 aes-256-cbc -iter 1000000 -out pk8.pem

=head1 STANDARDS

Test vectors from this PKCS#5 v2.0 implementation were posted to the
pkcs-tng mailing list using triple DES, DES and RC2 with high iteration
counts, several people confirmed that they could decrypt the private
keys produced and therefore, it can be assumed that the PKCS#5 v2.0
implementation is reasonably accurate at least as far as these
algorithms are concerned.

The format of PKCS#8 DSA (and other) private keys is not well documented:
it is hidden away in PKCS#11 v2.01, section 11.9. OpenSSL's default DSA
PKCS#8 private key format complies with this standard.

=head1 BUGS

There should be an option that prints out the encryption algorithm
in use and other details such as the iteration count.

=head1 SEE ALSO

L<openssl(1)>,
L<openssl-dsa(1)>,
L<openssl-rsa(1)>,
L<openssl-genrsa(1)>,
L<openssl-gendsa(1)>

=head1 HISTORY

The B<-iter> option was added in OpenSSL 1.1.0.

The B<-engine> option was deprecated in OpenSSL 3.0.

=head1 COPYRIGHT

Copyright 2000-2026 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>.

=cut
