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pkcs8(1ssl)
NAME
pkcs8 - PKCS#8 format private key conversion tool
SYNOPSIS
openssl pkcs8 [-topk8] [-inform PEM | DER] [-outform PEM | DER]
[-infilename] [-passinarg] [-outfilename] [-passoutarg] [-noiter]
[-nocrypt] [-nooct] [-embed] [-nsdb] [-v2alg] [-v1alg]
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.
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.
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
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
Specifies the output format. The options have the same meaning as
the -inform option.
-in filename
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.
-passin arg
Input file password source. For more information about the format
of arg, see the Pass Phrase Arguments section in openssl(1ssl).
-out filename
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.
-passoutarg
Output file password source. For more information about the format
of arg see the Pass Phrase Arguments section in openssl(1ssl).
-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, and should only be used when absolutely
necessary. Certain software such as some versions of Java code
signing software used unencrypted private keys.
-nooct Generates RSA private keys in a broken format used by some
software. Specifically the private key should be enclosed in a
octet string, but some software only includes the structure itself
without the surrounding octet string.
-embed 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 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.
-v2alg 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. If you are
using private keys only with OpenSSL then this doesn't matter.
The alg argument is the encryption algorithm to use. Valid values
include des, des3 and rc2. We recommend that des3 be used.
-v1alg 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.
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-RC2-40
PBE-SHA1-RC4-128 PBE-SHA1-RC4-40 PBE-SHA1-3DES PBE-
SHA1-2DES PBE-SHA1-RC2-128
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.
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.
NOTES
The encrypted form of PEM encoded 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 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.
RESTRICTIONS
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.
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
SEE ALSO
Commands: dsa(1ssl), rsa(1ssl), genrsa(1ssl), gendsa(1ssl)
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