or B parameters.
=back
=head1 KEY FORMATS
Various different formats are used by the pkcs8 utility. These are detailed
below.
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 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 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.
=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.
The encrypted form of a PEM encode PKCS#8 files uses the following
headers and footers:
-----BEGIN ENCRYPTED PRIVATE KEY-----
-----END ENCRYPTED PRIVATE KEY-----
The unencrypted form uses:
-----BEGIN PRIVATE KEY-----
-----END PRIVATE KEY-----
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
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, B, B, B
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, B, B, B, B, B
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):
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 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, L, L,
L
=head1 HISTORY
The B<-iter> option was added in OpenSSL 1.1.0.
=head1 COPYRIGHT
Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the OpenSSL license (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.
=cut