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