PKCS8(1) OpenSSL PKCS8(1)
NAME
pkcs8 - PKCS#8 format private key conversion tool
LIBRARY
libcrypto, -lcrypto
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 for- mat 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. Oth- erwise 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. 2000-07-22 0.9.6g 1 PKCS8(1) OpenSSL PKCS8(1) -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 appropri- ate password based encryption algorithm. With this option an unencrypted PrivateKeyInfo structure is expected or output. This option does not encrypt pri- vate keys at all and should only be used when abso- lutely necessary. Certain software such as some ver- sions 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 pri- vate 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 contain- ing the private key. -nsdb This option generates DSA keys in a broken format com- patible with Netscape private key databases. The Pri- vateKey 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 pbe- WithMD5AndDES-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 algo- rithms 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 recom- mended that des3 is used. 2000-07-22 0.9.6g 2 PKCS8(1) OpenSSL PKCS8(1) -v1 alg This option specifies a PKCS#5 v1.5 or PKCS#12 algo- rithm to use. A complete list of possible 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 han- dled 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 pro- tection 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 soft- ware. They are mentioned in PKCS#5 v2.0. They use either 64 bit RC2 or 56 bit DES. 2000-07-22 0.9.6g 3 PKCS8(1) OpenSSL PKCS8(1) 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 algo- rithms 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 compat- ible 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 tradi- tional 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 con- firmed 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, sec- tion 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. 2000-07-22 0.9.6g 4 PKCS8(1) OpenSSL PKCS8(1)
SEE ALSO
openssl_dsa(1), openssl_rsa(1), openssl_genrsa(1), openssl_gendsa(1) 2000-07-22 0.9.6g 5
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