Provided by: openssl_1.1.1f-1ubuntu2.23_amd64 
NAME
openssl-pkcs8, pkcs8 - PKCS#8 format private key conversion tool
SYNOPSIS
openssl pkcs8 [-help] [-topk8] [-inform PEM|DER] [-outform PEM|DER] [-in filename]
[-passin arg] [-out filename] [-passout arg] [-iter count] [-noiter] [-rand file...]
[-writerand file] [-nocrypt] [-traditional] [-v2 alg] [-v2prf alg] [-v1 alg] [-engine id]
[-scrypt] [-scrypt_N N] [-scrypt_r r] [-scrypt_p p]
DESCRIPTION
The pkcs8 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.
OPTIONS
-help
Print out a usage message.
-topk8
Normally a PKCS#8 private key is expected on input and a private key will be written
to the output file. With the -topk8 option the situation is reversed: it reads a
private key and writes a PKCS#8 format key.
-inform DER|PEM
This specifies the input format: see "KEY FORMATS" for more details. The default
format is PEM.
-outform DER|PEM
This specifies the output format: see "KEY FORMATS" for more details. The default
format is PEM.
-traditional
When this option is present and -topk8 is not a traditional format private key is
written.
-in 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.
-passin arg
The input file password source. For more information about the format of arg see the
PASS PHRASE ARGUMENTS section in openssl(1).
-out 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 not be the same as the input filename.
-passout arg
The output file password source. For more information about the format of arg see the
PASS PHRASE ARGUMENTS section in openssl(1).
-iter 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.
-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.
-rand file...
A file or files containing random data used to seed the random number generator.
Multiple files can be specified separated by an OS-dependent character. The separator
is ; for MS-Windows, , for OpenVMS, and : for all others.
[-writerand file]
Writes random data to the specified file upon exit. This can be used with a
subsequent -rand flag.
-v2 alg
This option sets the PKCS#5 v2.0 algorithm.
The alg argument is the encryption algorithm to use, valid values include aes128,
aes256 and des3. If this option isn't specified then aes256 is used.
-v2prf alg
This option sets the PRF algorithm to use with PKCS#5 v2.0. A typical value value
would be hmacWithSHA256. If this option isn't set then the default for the cipher is
used or hmacWithSHA256 if there is no default.
Some implementations may not support custom PRF algorithms and may require the
hmacWithSHA1 option to work.
-v1 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.
-engine id
Specifying an engine (by its unique id string) will cause pkcs8 to attempt to obtain a
functional reference to the specified engine, thus initialising it if needed. The
engine will then be set as the default for all available algorithms.
-scrypt
Uses the 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 -scrypt_N, -scrypt_r, -scrypt_p and -v2 options.
-scrypt_N N -scrypt_r r -scrypt_p p
Sets the scrypt N, r or p parameters.
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 -topk8 option is not used) then the
input file must be in PKCS#8 format. An encrypted key is expected unless -nocrypt is
included.
If -topk8 is not used and PEM mode is set the output file will be an unencrypted private
key in PKCS#8 format. If the -traditional option is used then a traditional format private
key is written instead.
If -topk8 is not used and DER mode is set the output file will be an unencrypted private
key in traditional DER format.
If -topk8 is used then any supported private key can be used for the input file in a
format specified by -inform. The output file will be encrypted PKCS#8 format using the
specified encryption parameters unless -nocrypt is included.
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.
PKCS#5 v1.5 and PKCS#12 algorithms.
Various algorithms can be used with the -v1 command line option, including PKCS#5 v1.5 and
PKCS#12. These are described in more detail below.
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.
PBE-SHA1-RC2-64, PBE-MD2-RC2-64, PBE-MD5-RC2-64, 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.
PBE-SHA1-RC4-128, PBE-SHA1-RC4-40, PBE-SHA1-3DES, PBE-SHA1-2DES, PBE-SHA1-RC2-128,
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.
EXAMPLES
Convert a private key to PKCS#8 format using default parameters (AES with 256 bit key and
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
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
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.
BUGS
There should be an option that prints out the encryption algorithm in use and other
details such as the iteration count.
SEE ALSO
dsa(1), rsa(1), genrsa(1), gendsa(1)
HISTORY
The -iter option was added in OpenSSL 1.1.0.
COPYRIGHT
Copyright 2000-2018 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 <https://www.openssl.org/source/license.html>.