5 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 When creating new PKCS#8 containers, use a given number of iterations on the password
83 in deriving the encryption key for the PKCS#8 output. High values increase the time
84 required to brute-force a PKCS#8 container.
88 PKCS#8 keys generated or input are normally PKCS#8 EncryptedPrivateKeyInfo
89 structures using an appropriate password based encryption algorithm. With
90 this option an unencrypted PrivateKeyInfo structure is expected or output.
91 This option does not encrypt private keys at all and should only be used
92 when absolutely necessary. Certain software such as some versions of Java
93 code signing software used unencrypted private keys.
97 This option generates RSA private keys in a broken format that some software
98 uses. Specifically the private key should be enclosed in a OCTET STRING
99 but some software just includes the structure itself without the
100 surrounding OCTET STRING.
104 This option generates DSA keys in a broken format. The DSA parameters are
105 embedded inside the PrivateKey structure. In this form the OCTET STRING
106 contains an ASN1 SEQUENCE consisting of two structures: a SEQUENCE containing
107 the parameters and an ASN1 INTEGER containing the private key.
111 This option generates DSA keys in a broken format compatible with Netscape
112 private key databases. The PrivateKey contains a SEQUENCE consisting of
113 the public and private keys respectively.
117 This option enables the use of PKCS#5 v2.0 algorithms. Normally PKCS#8
118 private keys are encrypted with the password based encryption algorithm
119 called B<pbeWithMD5AndDES-CBC> this uses 56 bit DES encryption but it
120 was the strongest encryption algorithm supported in PKCS#5 v1.5. Using
121 the B<-v2> option PKCS#5 v2.0 algorithms are used which can use any
122 encryption algorithm such as 168 bit triple DES or 128 bit RC2 however
123 not many implementations support PKCS#5 v2.0 yet. If you are just using
124 private keys with OpenSSL then this doesn't matter.
126 The B<alg> argument is the encryption algorithm to use, valid values include
127 B<des>, B<des3> and B<rc2>. It is recommended that B<des3> is used.
131 This option sets the PRF algorithm to use with PKCS#5 v2.0. A typical value
132 values would be B<hmacWithSHA256>. If this option isn't set then the default
133 for the cipher is used or B<hmacWithSHA1> if there is no default.
137 This option specifies a PKCS#5 v1.5 or PKCS#12 algorithm to use. A complete
138 list of possible algorithms is included below.
142 specifying an engine (by its unique B<id> string) will cause B<pkcs8>
143 to attempt to obtain a functional reference to the specified engine,
144 thus initialising it if needed. The engine will then be set as the default
145 for all available algorithms.
151 The encrypted form of a PEM encode PKCS#8 files uses the following
154 -----BEGIN ENCRYPTED PRIVATE KEY-----
155 -----END ENCRYPTED PRIVATE KEY-----
157 The unencrypted form uses:
159 -----BEGIN PRIVATE KEY-----
160 -----END PRIVATE KEY-----
162 Private keys encrypted using PKCS#5 v2.0 algorithms and high iteration
163 counts are more secure that those encrypted using the traditional
164 SSLeay compatible formats. So if additional security is considered
165 important the keys should be converted.
167 The default encryption is only 56 bits because this is the encryption
168 that most current implementations of PKCS#8 will support.
170 Some software may use PKCS#12 password based encryption algorithms
171 with PKCS#8 format private keys: these are handled automatically
172 but there is no option to produce them.
174 It is possible to write out DER encoded encrypted private keys in
175 PKCS#8 format because the encryption details are included at an ASN1
176 level whereas the traditional format includes them at a PEM level.
178 =head1 PKCS#5 v1.5 and PKCS#12 algorithms.
180 Various algorithms can be used with the B<-v1> command line option,
181 including PKCS#5 v1.5 and PKCS#12. These are described in more detail
186 =item B<PBE-MD2-DES PBE-MD5-DES>
188 These algorithms were included in the original PKCS#5 v1.5 specification.
189 They only offer 56 bits of protection since they both use DES.
191 =item B<PBE-SHA1-RC2-64 PBE-MD2-RC2-64 PBE-MD5-RC2-64 PBE-SHA1-DES>
193 These algorithms are not mentioned in the original PKCS#5 v1.5 specification
194 but they use the same key derivation algorithm and are supported by some
195 software. They are mentioned in PKCS#5 v2.0. They use either 64 bit RC2 or
198 =item B<PBE-SHA1-RC4-128 PBE-SHA1-RC4-40 PBE-SHA1-3DES PBE-SHA1-2DES PBE-SHA1-RC2-128 PBE-SHA1-RC2-40>
200 These algorithms use the PKCS#12 password based encryption algorithm and
201 allow strong encryption algorithms like triple DES or 128 bit RC2 to be used.
207 Convert a private from traditional to PKCS#5 v2.0 format using triple
210 openssl pkcs8 -in key.pem -topk8 -v2 des3 -out enckey.pem
212 Convert a private from traditional to PKCS#5 v2.0 format using AES with
213 256 bits in CBC mode and B<hmacWithSHA256> PRF:
215 openssl pkcs8 -in key.pem -topk8 -v2 aes-256-cbc -v2prf hmacWithSHA256 -out enckey.pem
217 Convert a private key to PKCS#8 using a PKCS#5 1.5 compatible algorithm
220 openssl pkcs8 -in key.pem -topk8 -out enckey.pem
222 Convert a private key to PKCS#8 using a PKCS#12 compatible algorithm
225 openssl pkcs8 -in key.pem -topk8 -out enckey.pem -v1 PBE-SHA1-3DES
227 Read a DER unencrypted PKCS#8 format private key:
229 openssl pkcs8 -inform DER -nocrypt -in key.der -out key.pem
231 Convert a private key from any PKCS#8 format to traditional format:
233 openssl pkcs8 -in pk8.pem -out key.pem
235 Convert a private key to PKCS#8 format, encrypting with AES-256 and with
236 one million iterations of the password:
238 openssl pkcs8 -in raw.pem -topk8 -v2 aes-256-cbc -iter 1000000 -out pk8.pem
242 Test vectors from this PKCS#5 v2.0 implementation were posted to the
243 pkcs-tng mailing list using triple DES, DES and RC2 with high iteration
244 counts, several people confirmed that they could decrypt the private
245 keys produced and Therefore it can be assumed that the PKCS#5 v2.0
246 implementation is reasonably accurate at least as far as these
247 algorithms are concerned.
249 The format of PKCS#8 DSA (and other) private keys is not well documented:
250 it is hidden away in PKCS#11 v2.01, section 11.9. OpenSSL's default DSA
251 PKCS#8 private key format complies with this standard.
255 There should be an option that prints out the encryption algorithm
256 in use and other details such as the iteration count.
258 PKCS#8 using triple DES and PKCS#5 v2.0 should be the default private
259 key format for OpenSSL: for compatibility several of the utilities use
260 the old format at present.
264 L<dsa(1)|dsa(1)>, L<rsa(1)|rsa(1)>, L<genrsa(1)|genrsa(1)>,
265 L<gendsa(1)|gendsa(1)>