5 pkcs8 - PKCS#8 format private key conversion tool
35 The B<pkcs8> command processes private keys in PKCS#8 format. It can handle
36 both unencrypted PKCS#8 PrivateKeyInfo format and EncryptedPrivateKeyInfo
37 format with a variety of PKCS#5 (v1.5 and v2.0) and PKCS#12 algorithms.
39 =head1 COMMAND OPTIONS
45 Print out a usage message.
49 Normally a PKCS#8 private key is expected on input and a traditional format
50 private key will be written. With the B<-topk8> option the situation is
51 reversed: it reads a traditional format private key and writes a PKCS#8
54 =item B<-inform DER|PEM>
56 This specifies the input format. If a PKCS#8 format key is expected on input
57 then either a B<DER> or B<PEM> encoded version of a PKCS#8 key will be
58 expected. Otherwise the B<DER> or B<PEM> format of the traditional format
61 =item B<-outform DER|PEM>
63 This specifies the output format, the options have the same meaning as the
68 This specifies the input filename to read a key from or standard input if this
69 option is not specified. If the key is encrypted a pass phrase will be
74 the input file password source. For more information about the format of B<arg>
75 see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)>.
77 =item B<-out filename>
79 This specifies the output filename to write a key to or standard output by
80 default. If any encryption options are set then a pass phrase will be
81 prompted for. The output filename should B<not> be the same as the input
86 the output file password source. For more information about the format of B<arg>
87 see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)>.
91 When creating new PKCS#8 containers, use a given number of iterations on
92 the password in deriving the encryption key for the PKCS#8 output.
93 High values increase the time required to brute-force a PKCS#8 container.
97 PKCS#8 keys generated or input are normally PKCS#8 EncryptedPrivateKeyInfo
98 structures using an appropriate password based encryption algorithm. With
99 this option an unencrypted PrivateKeyInfo structure is expected or output.
100 This option does not encrypt private keys at all and should only be used
101 when absolutely necessary. Certain software such as some versions of Java
102 code signing software used unencrypted private keys.
106 This option generates RSA private keys in a broken format that some software
107 uses. Specifically the private key should be enclosed in a OCTET STRING
108 but some software just includes the structure itself without the
109 surrounding OCTET STRING.
113 This option generates DSA keys in a broken format. The DSA parameters are
114 embedded inside the PrivateKey structure. In this form the OCTET STRING
115 contains an ASN1 SEQUENCE consisting of two structures: a SEQUENCE containing
116 the parameters and an ASN1 INTEGER containing the private key.
120 This option generates DSA keys in a broken format compatible with Netscape
121 private key databases. The PrivateKey contains a SEQUENCE consisting of
122 the public and private keys respectively.
126 This option enables the use of PKCS#5 v2.0 algorithms. Normally PKCS#8
127 private keys are encrypted with the password based encryption algorithm
128 called B<pbeWithMD5AndDES-CBC> this uses 56 bit DES encryption but it
129 was the strongest encryption algorithm supported in PKCS#5 v1.5. Using
130 the B<-v2> option PKCS#5 v2.0 algorithms are used which can use any
131 encryption algorithm such as 168 bit triple DES or 128 bit RC2 however
132 not many implementations support PKCS#5 v2.0 yet. If you are just using
133 private keys with OpenSSL then this doesn't matter.
135 The B<alg> argument is the encryption algorithm to use, valid values include
136 B<des>, B<des3> and B<rc2>. It is recommended that B<des3> is used.
140 This option sets the PRF algorithm to use with PKCS#5 v2.0. A typical value
141 values would be B<hmacWithSHA256>. If this option isn't set then the default
142 for the cipher is used or B<hmacWithSHA1> if there is no default.
146 This option specifies a PKCS#5 v1.5 or PKCS#12 algorithm to use. A complete
147 list of possible algorithms is included below.
151 specifying an engine (by its unique B<id> string) will cause B<pkcs8>
152 to attempt to obtain a functional reference to the specified engine,
153 thus initialising it if needed. The engine will then be set as the default
154 for all available algorithms.
158 uses the B<scrypt> algorithm for private key encryption using default
159 parameters: currently N=1024, r=8 and p=16 and AES in CBC mode with a 256 bit
160 key. These parameters can be modified using the B<-scrypt_N>, B<-scrypt_r>,
161 B<-scrypt_p> and B<-v2> options.
163 B<-scrypt_N N> B<-scrypt_r r> B<-scrypt_p p>
165 sets the scrypt B<N>, B<r> or B<p> parameters.
171 The encrypted form of a PEM encode PKCS#8 files uses the following
174 -----BEGIN ENCRYPTED PRIVATE KEY-----
175 -----END ENCRYPTED PRIVATE KEY-----
177 The unencrypted form uses:
179 -----BEGIN PRIVATE KEY-----
180 -----END PRIVATE KEY-----
182 Private keys encrypted using PKCS#5 v2.0 algorithms and high iteration
183 counts are more secure that those encrypted using the traditional
184 SSLeay compatible formats. So if additional security is considered
185 important the keys should be converted.
187 The default encryption is only 56 bits because this is the encryption
188 that most current implementations of PKCS#8 will support.
190 Some software may use PKCS#12 password based encryption algorithms
191 with PKCS#8 format private keys: these are handled automatically
192 but there is no option to produce them.
194 It is possible to write out DER encoded encrypted private keys in
195 PKCS#8 format because the encryption details are included at an ASN1
196 level whereas the traditional format includes them at a PEM level.
198 =head1 PKCS#5 v1.5 and PKCS#12 algorithms.
200 Various algorithms can be used with the B<-v1> command line option,
201 including PKCS#5 v1.5 and PKCS#12. These are described in more detail
206 =item B<PBE-MD2-DES PBE-MD5-DES>
208 These algorithms were included in the original PKCS#5 v1.5 specification.
209 They only offer 56 bits of protection since they both use DES.
211 =item B<PBE-SHA1-RC2-64 PBE-MD2-RC2-64 PBE-MD5-RC2-64 PBE-SHA1-DES>
213 These algorithms are not mentioned in the original PKCS#5 v1.5 specification
214 but they use the same key derivation algorithm and are supported by some
215 software. They are mentioned in PKCS#5 v2.0. They use either 64 bit RC2 or
218 =item B<PBE-SHA1-RC4-128 PBE-SHA1-RC4-40 PBE-SHA1-3DES PBE-SHA1-2DES PBE-SHA1-RC2-128 PBE-SHA1-RC2-40>
220 These algorithms use the PKCS#12 password based encryption algorithm and
221 allow strong encryption algorithms like triple DES or 128 bit RC2 to be used.
227 Convert a private from traditional to PKCS#5 v2.0 format using triple
230 openssl pkcs8 -in key.pem -topk8 -v2 des3 -out enckey.pem
232 Convert a private from traditional to PKCS#5 v2.0 format using AES with
233 256 bits in CBC mode and B<hmacWithSHA256> PRF:
235 openssl pkcs8 -in key.pem -topk8 -v2 aes-256-cbc -v2prf hmacWithSHA256 -out enckey.pem
237 Convert a private key to PKCS#8 using a PKCS#5 1.5 compatible algorithm
240 openssl pkcs8 -in key.pem -topk8 -out enckey.pem
242 Convert a private key to PKCS#8 using a PKCS#12 compatible algorithm
245 openssl pkcs8 -in key.pem -topk8 -out enckey.pem -v1 PBE-SHA1-3DES
247 Read a DER unencrypted PKCS#8 format private key:
249 openssl pkcs8 -inform DER -nocrypt -in key.der -out key.pem
251 Convert a private key from any PKCS#8 format to traditional format:
253 openssl pkcs8 -in pk8.pem -out key.pem
255 Convert a private key to PKCS#8 format, encrypting with AES-256 and with
256 one million iterations of the password:
258 openssl pkcs8 -in raw.pem -topk8 -v2 aes-256-cbc -iter 1000000 -out pk8.pem
262 Test vectors from this PKCS#5 v2.0 implementation were posted to the
263 pkcs-tng mailing list using triple DES, DES and RC2 with high iteration
264 counts, several people confirmed that they could decrypt the private
265 keys produced and Therefore it can be assumed that the PKCS#5 v2.0
266 implementation is reasonably accurate at least as far as these
267 algorithms are concerned.
269 The format of PKCS#8 DSA (and other) private keys is not well documented:
270 it is hidden away in PKCS#11 v2.01, section 11.9. OpenSSL's default DSA
271 PKCS#8 private key format complies with this standard.
275 There should be an option that prints out the encryption algorithm
276 in use and other details such as the iteration count.
278 PKCS#8 using triple DES and PKCS#5 v2.0 should be the default private
279 key format for OpenSSL: for compatibility several of the utilities use
280 the old format at present.
284 L<dsa(1)>, L<rsa(1)>, L<genrsa(1)>,
289 The B<-iter> option was added to OpenSSL 1.1.0.