NAME
pkcs8 - PKCS#8 format private key conversion tool
SYNOPSIS
ooppeennssssll ppkkccss88 [-ttooppkk88] [-iinnffoorrmm PPEEMM||DDEERR] [-oouuttffoorrmm PPEEMM||DDEERR] [-iinn
ffiilleennaammee] [-ppaassssiinn aarrgg] [-oouutt ffiilleennaammee] [-ppaassssoouutt aarrgg] [-nnooiitteerr]
[-nnooccrryypptt] [-nnoooocctt] [-eemmbbeedd] [-nnssddbb] [-vv22 aallgg] [-vv11 aallgg] [-eennggiinnee iidd]
DESCRIPTION
The ppkkccss88 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.
CCOOMMMMAANNDD OOPPTTIIOONNSS-ttooppkk88
Normally a PKCS#8 private key is expected on input and a
traditional format private key will be written. With the -ttooppkk88
option the situation is reversed: it reads a traditional formatprivate key and writes a PKCS#8 format key.
-iinnffoorrmm DDEERR||PPEEMM
This specifies the input format. If a PKCS#8 format key is expected
on input then either a DDEERR or PPEEMM encoded version of a PKCS#8 key
will be expected. Otherwise the DDEERR or PPEEMM format of the traditional format private key is used.-oouuttffoorrmm DDEERR||PPEEMM
This specifies the output format, the options have the same meaningas the -iinnffoorrmm option.
-iinn ffiilleennaammee
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.-ppaassssiinn aarrgg
the input file password source. For more information about the format of aarrgg see the PPAASSSS PPHHRRAASSEE AARRGGUUMMEENNTTSS section in openssl(1).-oouutt ffiilleennaammee
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 nnoott be the same as the input filename.-ppaassssoouutt aarrgg
the output file password source. For more information about the format of aarrgg see the PPAASSSS PPHHRRAASSEE AARRGGUUMMEENNTTSS section in openssl(1).-nnooccrryypptt
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.-nnoooocctt
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.-eemmbbeedd
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.-nnssddbb
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.-vv22 aallgg
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 ppbbeeWWiitthhMMDD55AAnnddDDEESS-CCBBCC this uses 56 bit
DES encryption but it was the strongest encryption algorithmsupported in PKCS#5 v1.5. Using the -vv22 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 implementationssupport PKCS#5 v2.0 yet. If you are just using private keys with
OpenSSL then this doesn't matter. The aallgg argument is the encryption algorithm to use, valid values include ddeess, ddeess33 and rrcc22. It is recommended that ddeess33 is used.-vv11 aallgg
This option specifies a PKCS#5 v1.5 or PKCS#12 algorithm to use. A
complete list of possible algorithms is included below.-eennggiinnee iidd
specifying an engine (by it's unique iidd string) will cause rreeqq 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. NNOOTTEESSThe 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 encryptionthat 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 inPKCS#8 format because the encryption details are included at an ASN1
level whereas the traditional format includes them at a PEM level.PPKKCCSS##55 vv11..55 aanndd PPKKCCSS##1122 aallggoorriitthhmmss..
Various algorithms can be used with the -vv11 command line option,
including PKCS#5 v1.5 and PKCS#12. These are described in more detail
below.PPBBEE-MMDD22-DDEESS PPBBEE-MMDD55-DDEESS
These algorithms were included in the original PKCS#5 v1.5
specification. They only offer 56 bits of protection since they both use DES.PPBBEE-SSHHAA11-RRCC22-6644 PPBBEE-MMDD22-RRCC22-6644 PPBBEE-MMDD55-RRCC22-6644 PPBBEE-SSHHAA11-DDEESS
These algorithms are not mentioned in the original PKCS#5 v1.5
specification but they use the same key derivation algorithm andare supported by some software. They are mentioned in PKCS#5 v2.0.
They use either 64 bit RC2 or 56 bit DES.PPBBEE-SSHHAA11-RRCC44-112288 PPBBEE-SSHHAA11-RRCC44-4400 PPBBEE-SSHHAA11-33DDEESS PPBBEE-SSHHAA11-22DDEESS
PPBBEE-SSHHAA11-RRCC22-112288 PPBBEE-SSHHAA11-RRCC22-4400
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. EEXXAAMMPPLLEESSConvert 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
STANDARDSTest 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 privatekeys 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.SEE ALSO
dsa(1), rsa(1), genrsa(1), gendsa(1)0.9.7l 2003-01-30 PKCS8(1)