pkcs8Namepkcs8 -- PKCS#8 format private key conversion tool Synopsisopenssl pkcs8
[-topk8]
[-inform PEM|DER]
[-outform PEM|DER]
[-in filename]
[-passin arg]
[-out filename]
[-passout arg]
[-noiter]
[-nocrypt]
[-nooct]
[-embed]
[-nsdb]
[-v2 alg]
[-v1 alg]
[-engine id] |
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.
COMMAND OPTIONS - -topk8
Normally a PKCS#8 private key is expected on input and a
traditional format private key will be written. With the
-topk8 option the situation
is reversed: it reads a traditional format private key and
writes a PKCS#8 format key.
- -inform DER|PEM
This 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.
- -outform DER|PEM
This specifies the output format, the options have the same
meaning as the -inform
option.
- -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).
- -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.
- -nooct
This option generates RSA private keys in a broken format
that some software uses. Specifically the private key should
be enclosed in a OCTET STRING but some software just includes
the structure itself without the surrounding OCTET STRING.
- -embed
This option 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.
- -nsdb
This option generates DSA keys in a broken format compatible
with Netscape private key databases. The PrivateKey contains
a SEQUENCE consisting of the public and private keys
respectively.
- -v2 alg
This option enables the use of PKCS#5 v2.0 algorithms.
Normally PKCS#8 private keys are encrypted with the password
based encryption algorithm called pbeWithMD5AndDES-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 yet. If you are just using private keys
with OpenSSL then this doesn't matter.
The alg argument is the
encryption algorithm to use, valid values include des, des3 and rc2. It is recommended that des3 is used.
- -v1 alg
This option specifies a PKCS#5 v1.5 or PKCS#12 algorithm to
use. A complete list of possible algorithms is included
below.
- -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.
NOTES 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.
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.
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 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-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 format to traditional format:
openssl pkcs8 -in pk8.pem -out key.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.
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 at present.
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