pkcs8(1ssl)pkcs8(1ssl)NAMEpkcs8 - PKCS#8 format private key conversion tool
openssl pkcs8 [-topk8] [-inform PEM | DER] [-outform PEM | DER]
[-infilename] [-passinarg] [-outfilename] [-passoutarg] [-noiter]
[-nocrypt] [-nooct] [-embed] [-nsdb] [-v2alg] [-v1alg]
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. Therefore it can be assumed that the PKCS#5 v2.0 imple‐
mentation is reasonably accurate, at least as far as these algorithms
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.
Normally a PKCS#8 private key is expected on input and a traditional
format private key will be written. With the -topk8 option the situa‐
tion is reversed; it reads a traditional format private key and writes
a PKCS#8 format key. Specifies the input format. If a PKCS#8 format
key is expected on input then either a DER or PEM encoded version of a
PKCS#8 key will be expected. Otherwise the DER or PEM format of the
traditional format private key is used. Specifies the output format.
The options have the same meaning as the -inform option. Specifies the
input filename to read a key from or standard input if this option is
not specified. If the key is encrypted there is a prompt for a pass
phrase. Input file password source. For more information about the
format of arg, see the Pass Phrase Arguments section in openssl(1ssl).
Specifies the output filename to write a key to or standard output by
default. If any encryption options are set, there is a prompt for a
pass phrase. The output filename should not be the same as the input
filename. Output file password source. For more information about the
format of arg see the Pass Phrase Arguments section in openssl(1ssl).
PKCS#8 keys generated or input are normally PKCS#8 EncryptedPrivateKey‐
Info structures using an appropriate password based encryption algo‐
rithm. With this option an unencrypted PrivateKeyInfo structure is
expected or output. This option does not encrypt private keys, and
should only be used when absolutely necessary. Certain software such as
some versions of Java code signing software used unencrypted private
keys. Generates RSA private keys in a broken format used by some soft‐
ware. Specifically the private key should be enclosed in a octet
string, but some software only includes the structure itself without
the surrounding octet string. Generates DSA keys in a broken format.
The DSA parameters are embedded inside the PrivateKey structure. In
this form the octet string contains an ASN1 sequence consisting of two
structures: a sequence containing the parameters and an ASN1 integer
containing the private key. Generates DSA keys in a broken format com‐
patible with Netscape private key databases. The PrivateKey contains a
sequence consisting of the public and private keys respectively.
Enables the use of PKCS#5 v2.0 algorithms. Normally PKCS#8 private keys
are encrypted with the password based encryption algorithm called pbe‐
WithMD5AndDES-CBC. This uses 56-bit DES encryption, but it was the
strongest encryption algorithm supported in PKCS#5 v1.5. Using the -v2
option PKCS#5 v2.0 algorithms are used which can use any encryption
algorithm such as 168-bit triple DES or 128-bit RC2. However, not many
implementations support PKCS#5 v2.0. If you are using private keys only
with OpenSSL then this doesn't matter.
The alg argument is the encryption algorithm to use. Valid val‐
ues include des, des3 and rc2. We recommend that des3 be used.
Specifies a PKCS#5 v1.5 or PKCS#12 algorithm to use. A complete
list of possible algorithms is included below.
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. These algorithms were included in the original PKCS#5 v1.5
specification. They only offer 56 bits of protection since they both
use 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. These algorithms use the PKCS#12
password based encryption algorithm and allow strong encryption algo‐
rithms like triple DES or 128-bit RC2 to be used.
The pkcs8 command processes private keys in PKCS#8 format. It can han‐
dle both unencrypted PKCS#8 PrivateKeyInfo format and EncryptedPri‐
vateKeyInfo format with a variety of PKCS#5 (v1.5 and v2.0) and PKCS#12
The encrypted form of PEM encoded PKCS#8 files uses the following head‐
ers 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 than those encrypted using the traditional
SSLeay compatible formats. If additional security is important, the
keys should be converted.
The default encryption is only 56 bits because this is the encryption
that most current implementations of PKCS#8 will support.
Some software may use PKCS#12 password based encryption algorithms with
PKCS#8 format private keys. These are handled automatically, but there
is no option to produce them.
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.
There should be an option that prints out the encryption algorithm in
use and other details such as the iteration count.
PKCS#8 using triple DES and PKCS#5 v2.0 should be the default private
key format for OpenSSL. For compatibility, several of the utilities use
the old format.
Convert a private from traditional 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#8 using a PKCS#5 1.5 compatible algorithm
(DES): openssl pkcs8-in key.pem -topk8 -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-
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 format to traditional format:
openssl pkcs8-in pk8.pem -out key.pem
Commands: dsa(1ssl), rsa(1ssl), genrsa(1ssl), gendsa(1ssl)pkcs8(1ssl)