6 pkcs8 - PKCS#8 format private key conversion tool
30 The B<pkcs8> command processes private keys in PKCS#8 format. It can handle
31 both unencrypted PKCS#8 PrivateKeyInfo format and EncryptedPrivateKeyInfo
32 format with a variety of PKCS#5 (v1.5 and v2.0) and PKCS#12 algorithms.
34 =head1 COMMAND OPTIONS
40 Normally a PKCS#8 private key is expected on input and a traditional format
41 private key will be written. With the B<-topk8> option the situation is
42 reversed: it reads a traditional format private key and writes a PKCS#8
45 =item B<-inform DER|PEM>
47 This specifies the input format. If a PKCS#8 format key is expected on input
48 then either a B<DER> or B<PEM> encoded version of a PKCS#8 key will be
49 expected. Otherwise the B<DER> or B<PEM> format of the traditional format
52 =item B<-outform DER|PEM>
54 This specifies the output format, the options have the same meaning as the
59 This specifies the input filename to read a key from or standard input if this
60 option is not specified. If the key is encrypted a pass phrase will be
65 the input file password source. For more information about the format of B<arg>
66 see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)|openssl(1)>.
68 =item B<-out filename>
70 This specifies the output filename to write a key to or standard output by
71 default. If any encryption options are set then a pass phrase will be
72 prompted for. The output filename should B<not> be the same as the input
77 the output file password source. For more information about the format of B<arg>
78 see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)|openssl(1)>.
82 PKCS#8 keys generated or input are normally PKCS#8 EncryptedPrivateKeyInfo
83 structures using an appropriate password based encryption algorithm. With
84 this option an unencrypted PrivateKeyInfo structure is expected or output.
85 This option does not encrypt private keys at all and should only be used
86 when absolutely necessary. Certain software such as some versions of Java
87 code signing software used unencrypted private keys.
91 This option generates RSA private keys in a broken format that some software
92 uses. Specifically the private key should be enclosed in a OCTET STRING
93 but some software just includes the structure itself without the
94 surrounding OCTET STRING.
98 This option generates DSA keys in a broken format. The DSA parameters are
99 embedded inside the PrivateKey structure. In this form the OCTET STRING
100 contains an ASN1 SEQUENCE consisting of two structures: a SEQUENCE containing
101 the parameters and an ASN1 INTEGER containing the private key.
105 This option generates DSA keys in a broken format compatible with Netscape
106 private key databases. The PrivateKey contains a SEQUENCE consisting of
107 the public and private keys respectively.
111 This option enables the use of PKCS#5 v2.0 algorithms. Normally PKCS#8
112 private keys are encrypted with the password based encryption algorithm
113 called B<pbeWithMD5AndDES-CBC> this uses 56 bit DES encryption but it
114 was the strongest encryption algorithm supported in PKCS#5 v1.5. Using
115 the B<-v2> option PKCS#5 v2.0 algorithms are used which can use any
116 encryption algorithm such as 168 bit triple DES or 128 bit RC2 however
117 not many implementations support PKCS#5 v2.0 yet. If you are just using
118 private keys with OpenSSL then this doesn't matter.
120 The B<alg> argument is the encryption algorithm to use, valid values include
121 B<des>, B<des3> and B<rc2>. It is recommended that B<des3> is used.
125 This option sets the PRF algorithm to use with PKCS#5 v2.0. A typical value
126 values would be B<hmacWithSHA256>. If this option isn't set then the default
127 for the cipher is used or B<hmacWithSHA1> if there is no default.
131 This option specifies a PKCS#5 v1.5 or PKCS#12 algorithm to use. A complete
132 list of possible algorithms is included below.
136 specifying an engine (by its unique B<id> string) will cause B<pkcs8>
137 to attempt to obtain a functional reference to the specified engine,
138 thus initialising it if needed. The engine will then be set as the default
139 for all available algorithms.
145 The encrypted form of a PEM encode PKCS#8 files uses the following
148 -----BEGIN ENCRYPTED PRIVATE KEY-----
149 -----END ENCRYPTED PRIVATE KEY-----
151 The unencrypted form uses:
153 -----BEGIN PRIVATE KEY-----
154 -----END PRIVATE KEY-----
156 Private keys encrypted using PKCS#5 v2.0 algorithms and high iteration
157 counts are more secure that those encrypted using the traditional
158 SSLeay compatible formats. So if additional security is considered
159 important the keys should be converted.
161 The default encryption is only 56 bits because this is the encryption
162 that most current implementations of PKCS#8 will support.
164 Some software may use PKCS#12 password based encryption algorithms
165 with PKCS#8 format private keys: these are handled automatically
166 but there is no option to produce them.
168 It is possible to write out DER encoded encrypted private keys in
169 PKCS#8 format because the encryption details are included at an ASN1
170 level whereas the traditional format includes them at a PEM level.
172 =head1 PKCS#5 v1.5 and PKCS#12 algorithms.
174 Various algorithms can be used with the B<-v1> command line option,
175 including PKCS#5 v1.5 and PKCS#12. These are described in more detail
180 =item B<PBE-MD2-DES PBE-MD5-DES>
182 These algorithms were included in the original PKCS#5 v1.5 specification.
183 They only offer 56 bits of protection since they both use DES.
185 =item B<PBE-SHA1-RC2-64 PBE-MD2-RC2-64 PBE-MD5-RC2-64 PBE-SHA1-DES>
187 These algorithms are not mentioned in the original PKCS#5 v1.5 specification
188 but they use the same key derivation algorithm and are supported by some
189 software. They are mentioned in PKCS#5 v2.0. They use either 64 bit RC2 or
192 =item B<PBE-SHA1-RC4-128 PBE-SHA1-RC4-40 PBE-SHA1-3DES PBE-SHA1-2DES PBE-SHA1-RC2-128 PBE-SHA1-RC2-40>
194 These algorithms use the PKCS#12 password based encryption algorithm and
195 allow strong encryption algorithms like triple DES or 128 bit RC2 to be used.
201 Convert a private from traditional to PKCS#5 v2.0 format using triple
204 openssl pkcs8 -in key.pem -topk8 -v2 des3 -out enckey.pem
206 Convert a private from traditional to PKCS#5 v2.0 format using AES with
207 256 bits in CBC mode and B<hmacWithSHA256> PRF:
209 openssl pkcs8 -in key.pem -topk8 -v2 aes-256-cbc -v2prf hmacWithSHA256 -out enckey.pem
211 Convert a private key to PKCS#8 using a PKCS#5 1.5 compatible algorithm
214 openssl pkcs8 -in key.pem -topk8 -out enckey.pem
216 Convert a private key to PKCS#8 using a PKCS#12 compatible algorithm
219 openssl pkcs8 -in key.pem -topk8 -out enckey.pem -v1 PBE-SHA1-3DES
221 Read a DER unencrypted PKCS#8 format private key:
223 openssl pkcs8 -inform DER -nocrypt -in key.der -out key.pem
225 Convert a private key from any PKCS#8 format to traditional format:
227 openssl pkcs8 -in pk8.pem -out key.pem
231 Test vectors from this PKCS#5 v2.0 implementation were posted to the
232 pkcs-tng mailing list using triple DES, DES and RC2 with high iteration
233 counts, several people confirmed that they could decrypt the private
234 keys produced and Therefore it can be assumed that the PKCS#5 v2.0
235 implementation is reasonably accurate at least as far as these
236 algorithms are concerned.
238 The format of PKCS#8 DSA (and other) private keys is not well documented:
239 it is hidden away in PKCS#11 v2.01, section 11.9. OpenSSL's default DSA
240 PKCS#8 private key format complies with this standard.
244 There should be an option that prints out the encryption algorithm
245 in use and other details such as the iteration count.
247 PKCS#8 using triple DES and PKCS#5 v2.0 should be the default private
248 key format for OpenSSL: for compatibility several of the utilities use
249 the old format at present.
253 L<dsa(1)|dsa(1)>, L<rsa(1)|rsa(1)>, L<genrsa(1)|genrsa(1)>,
254 L<gendsa(1)|gendsa(1)>