openssl-pkcs8 - PKCS#8 format private key conversion command
openssl pkcs8 [
-help] [
-topk8] [
-inform
DER|
PEM] [
-outform DER|
PEM] [
-in
filename] [
-passin arg] [
-out filename] [
-passout arg] [
-iter count] [
-noiter] [
-nocrypt] [
-traditional] [
-v2 alg] [
-v2prf alg] [
-v1 alg] [
-scrypt] [
-scrypt_N N] [
-scrypt_r r] [
-scrypt_p
p] [
-rand files] [
-writerand file] [
-engine id] [
-provider name] [
-provider-path path] [
-propquery propq]
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.
- -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, -outform
DER| PEM
- The input and formats; the default is PEM. See
openssl-format-options(1) for details.
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.
- -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, -passout arg
- The password source for the input and output file. For more
information about the format of arg see
openssl-passphrase-options(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.
-
-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.
- -noiter
- When creating new PKCS#8 containers, use 1 as iteration
count.
- -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.
-
-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.
- -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.
-
-rand files, -writerand
file
- See "Random State Options" in openssl(1)
for details.
-
-engine id
- See "Engine Options" in openssl(1). This
option is deprecated.
-
-provider name
-
-provider-path path
-
-propquery propq
- See "Provider Options" in openssl(1),
provider(7), and property(7).
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.
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.
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
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.
There should be an option that prints out the encryption algorithm in use and
other details such as the iteration count.
openssl(1),
openssl-dsa(1),
openssl-rsa(1),
openssl-genrsa(1),
openssl-gendsa(1)
The
-iter option was added in OpenSSL 1.1.0.
The
-engine option was deprecated in OpenSSL 3.0.
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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>.