OpenSL pkcs8(1openssl)
NAME
pkcs8 - PKCS#8 format private key conversion tool
SYNOPSIS
openssl pkcs8 [-topk8] [-inform PEMDER] [-outform PEMDER]
[-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.
COMAND 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 DERPEM
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 DERPEM
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 PAS 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
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the output file password source. For more information
about the format of arg see the PAS 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 OpenSL 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.
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-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 it's unique id string) will
cause req 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 SLeay 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
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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-RC2-128 PBE-SHA1-RC2-40
PBE-SHA1-RC4-128 PBE-SHA1-RC4-40 PBE-SHA1-3DES PBE-SHA1-2DES
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. OpenSL's default DSA PKCS#8 private key
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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 OpenSL: for compatibility
several of the utilities use the old format at present.
SEE ALSO
dsa(1), rsa(1), genrsa(1), gendsa(1)
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