5 openssl-pkcs8 - PKCS#8 format private key conversion tool
12 [B<-inform> B<DER>|B<PEM>]
13 [B<-outform> B<DER>|B<PEM>]
21 [B<-writerand> I<file>]
33 =for openssl ifdef engine scrypt scrypt_N scrypt_r scrypt_p
37 This command processes private keys in PKCS#8 format. It can handle
38 both unencrypted PKCS#8 PrivateKeyInfo format and EncryptedPrivateKeyInfo
39 format with a variety of PKCS#5 (v1.5 and v2.0) and PKCS#12 algorithms.
47 Print out a usage message.
51 Normally a PKCS#8 private key is expected on input and a private key will be
52 written to the output file. With the B<-topk8> option the situation is
53 reversed: it reads a private key and writes a PKCS#8 format key.
55 =item B<-inform> B<DER>|B<PEM>
57 This specifies the input format: see L<KEY FORMATS> for more details. The default
60 =item B<-outform> B<DER>|B<PEM>
62 This specifies the output format: see L<KEY FORMATS> for more details. The default
67 When this option is present and B<-topk8> is not a traditional format private
70 =item B<-in> I<filename>
72 This specifies the input filename to read a key from or standard input if this
73 option is not specified. If the key is encrypted a pass phrase will be
76 =item B<-passin> I<arg>, B<-passout> I<arg>
78 The password source for the input and output file.
79 For more information about the format of B<arg>
80 see L<openssl(1)/Pass Phrase Options>.
82 =item B<-out> I<filename>
84 This specifies the output filename to write a key to or standard output by
85 default. If any encryption options are set then a pass phrase will be
86 prompted for. The output filename should B<not> be the same as the input
89 =item B<-iter> I<count>
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.
104 =item B<-rand> I<files>
106 The files containing random data used to seed the random number generator.
107 Multiple files can be specified separated by an OS-dependent character.
108 The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
111 =item B<-writerand> I<file>
113 Writes random data to the specified I<file> upon exit.
114 This can be used with a subsequent B<-rand> flag.
118 This option sets the PKCS#5 v2.0 algorithm.
120 The I<alg> argument is the encryption algorithm to use, valid values include
121 B<aes128>, B<aes256> and B<des3>. If this option isn't specified then B<aes256>
124 =item B<-v2prf> I<alg>
126 This option sets the PRF algorithm to use with PKCS#5 v2.0. A typical value
127 value would be B<hmacWithSHA256>. If this option isn't set then the default
128 for the cipher is used or B<hmacWithSHA256> if there is no default.
130 Some implementations may not support custom PRF algorithms and may require
131 the B<hmacWithSHA1> option to work.
135 This option indicates a PKCS#5 v1.5 or PKCS#12 algorithm should be used. Some
136 older implementations may not support PKCS#5 v2.0 and may require this option.
137 If not specified PKCS#5 v2.0 form is used.
139 =item B<-engine> I<id>
141 Specifying an engine (by its unique I<id> string) will cause this command
142 to attempt to obtain a functional reference to the specified engine,
143 thus initialising it if needed. The engine will then be set as the default
144 for all available algorithms.
148 Uses the B<scrypt> algorithm for private key encryption using default
149 parameters: currently N=16384, r=8 and p=1 and AES in CBC mode with a 256 bit
150 key. These parameters can be modified using the B<-scrypt_N>, B<-scrypt_r>,
151 B<-scrypt_p> and B<-v2> options.
153 =item B<-scrypt_N> I<N>, B<-scrypt_r> I<r>, B<-scrypt_p> I<p>
155 Sets the scrypt I<N>, I<r> or I<p> parameters.
161 Various different formats are used by this command. These are detailed
164 If a key is being converted from PKCS#8 form (i.e. the B<-topk8> option is
165 not used) then the input file must be in PKCS#8 format. An encrypted
166 key is expected unless B<-nocrypt> is included.
168 If B<-topk8> is not used and B<PEM> mode is set the output file will be an
169 unencrypted private key in PKCS#8 format. If the B<-traditional> option is
170 used then a traditional format private key is written instead.
172 If B<-topk8> is not used and B<DER> mode is set the output file will be an
173 unencrypted private key in traditional DER format.
175 If B<-topk8> is used then any supported private key can be used for the input
176 file in a format specified by B<-inform>. The output file will be encrypted
177 PKCS#8 format using the specified encryption parameters unless B<-nocrypt>
182 By default, when converting a key to PKCS#8 format, PKCS#5 v2.0 using 256 bit
183 AES with HMAC and SHA256 is used.
185 Some older implementations do not support PKCS#5 v2.0 format and require
186 the older PKCS#5 v1.5 form instead, possibly also requiring insecure weak
187 encryption algorithms such as 56 bit DES.
189 The encrypted form of a PEM encode PKCS#8 files uses the following
192 -----BEGIN ENCRYPTED PRIVATE KEY-----
193 -----END ENCRYPTED PRIVATE KEY-----
195 The unencrypted form uses:
197 -----BEGIN PRIVATE KEY-----
198 -----END PRIVATE KEY-----
200 Private keys encrypted using PKCS#5 v2.0 algorithms and high iteration
201 counts are more secure that those encrypted using the traditional
202 SSLeay compatible formats. So if additional security is considered
203 important the keys should be converted.
205 It is possible to write out DER encoded encrypted private keys in
206 PKCS#8 format because the encryption details are included at an ASN1
207 level whereas the traditional format includes them at a PEM level.
209 =head1 PKCS#5 V1.5 AND PKCS#12 ALGORITHMS
211 Various algorithms can be used with the B<-v1> command line option,
212 including PKCS#5 v1.5 and PKCS#12. These are described in more detail
217 =item B<PBE-MD2-DES PBE-MD5-DES>
219 These algorithms were included in the original PKCS#5 v1.5 specification.
220 They only offer 56 bits of protection since they both use DES.
222 =item B<PBE-SHA1-RC2-64>, B<PBE-MD2-RC2-64>, B<PBE-MD5-RC2-64>, B<PBE-SHA1-DES>
224 These algorithms are not mentioned in the original PKCS#5 v1.5 specification
225 but they use the same key derivation algorithm and are supported by some
226 software. They are mentioned in PKCS#5 v2.0. They use either 64 bit RC2 or
229 =item B<PBE-SHA1-RC4-128>, B<PBE-SHA1-RC4-40>, B<PBE-SHA1-3DES>, B<PBE-SHA1-2DES>, B<PBE-SHA1-RC2-128>, B<PBE-SHA1-RC2-40>
231 These algorithms use the PKCS#12 password based encryption algorithm and
232 allow strong encryption algorithms like triple DES or 128 bit RC2 to be used.
238 Convert a private key to PKCS#8 format using default parameters (AES with
239 256 bit key and B<hmacWithSHA256>):
241 openssl pkcs8 -in key.pem -topk8 -out enckey.pem
243 Convert a private key to PKCS#8 unencrypted format:
245 openssl pkcs8 -in key.pem -topk8 -nocrypt -out enckey.pem
247 Convert a private key to PKCS#5 v2.0 format using triple DES:
249 openssl pkcs8 -in key.pem -topk8 -v2 des3 -out enckey.pem
251 Convert a private key to PKCS#5 v2.0 format using AES with 256 bits in CBC
252 mode and B<hmacWithSHA512> PRF:
254 openssl pkcs8 -in key.pem -topk8 -v2 aes-256-cbc -v2prf hmacWithSHA512 -out enckey.pem
256 Convert a private key to PKCS#8 using a PKCS#5 1.5 compatible algorithm
259 openssl pkcs8 -in key.pem -topk8 -v1 PBE-MD5-DES -out enckey.pem
261 Convert a private key to PKCS#8 using a PKCS#12 compatible algorithm
264 openssl pkcs8 -in key.pem -topk8 -out enckey.pem -v1 PBE-SHA1-3DES
266 Read a DER unencrypted PKCS#8 format private key:
268 openssl pkcs8 -inform DER -nocrypt -in key.der -out key.pem
270 Convert a private key from any PKCS#8 encrypted format to traditional format:
272 openssl pkcs8 -in pk8.pem -traditional -out key.pem
274 Convert a private key to PKCS#8 format, encrypting with AES-256 and with
275 one million iterations of the password:
277 openssl pkcs8 -in key.pem -topk8 -v2 aes-256-cbc -iter 1000000 -out pk8.pem
281 Test vectors from this PKCS#5 v2.0 implementation were posted to the
282 pkcs-tng mailing list using triple DES, DES and RC2 with high iteration
283 counts, several people confirmed that they could decrypt the private
284 keys produced and Therefore it can be assumed that the PKCS#5 v2.0
285 implementation is reasonably accurate at least as far as these
286 algorithms are concerned.
288 The format of PKCS#8 DSA (and other) private keys is not well documented:
289 it is hidden away in PKCS#11 v2.01, section 11.9. OpenSSL's default DSA
290 PKCS#8 private key format complies with this standard.
294 There should be an option that prints out the encryption algorithm
295 in use and other details such as the iteration count.
302 L<openssl-genrsa(1)>,
307 The B<-iter> option was added in OpenSSL 1.1.0.
311 Copyright 2000-2019 The OpenSSL Project Authors. All Rights Reserved.
313 Licensed under the Apache License 2.0 (the "License"). You may not use
314 this file except in compliance with the License. You can obtain a copy
315 in the file LICENSE in the source distribution or at
316 L<https://www.openssl.org/source/license.html>.