pkcs8 - PKCS#8 format private key conversion tool
SYNOPSIS
openssl 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]
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
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
algorithms is included below.
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
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.
dsa(1), rsa(1), genrsa(1), gendsa(1)
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