5 pkcs8 - PKCS#8 format private key conversion tool
34 The B<pkcs8> command processes private keys in PKCS#8 format. It can handle
35 both unencrypted PKCS#8 PrivateKeyInfo format and EncryptedPrivateKeyInfo
36 format with a variety of PKCS#5 (v1.5 and v2.0) and PKCS#12 algorithms.
38 =head1 COMMAND OPTIONS
44 Normally a PKCS#8 private key is expected on input and a traditional format
45 private key will be written. With the B<-topk8> option the situation is
46 reversed: it reads a traditional format private key and writes a PKCS#8
49 =item B<-inform DER|PEM>
51 This specifies the input format. If a PKCS#8 format key is expected on input
52 then either a B<DER> or B<PEM> encoded version of a PKCS#8 key will be
53 expected. Otherwise the B<DER> or B<PEM> format of the traditional format
56 =item B<-outform DER|PEM>
58 This specifies the output format, the options have the same meaning as the
63 This specifies the input filename to read a key from or standard input if this
64 option is not specified. If the key is encrypted a pass phrase will be
69 the input file password source. For more information about the format of B<arg>
70 see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)|openssl(1)>.
72 =item B<-out filename>
74 This specifies the output filename to write a key to or standard output by
75 default. If any encryption options are set then a pass phrase will be
76 prompted for. The output filename should B<not> be the same as the input
81 the output file password source. For more information about the format of B<arg>
82 see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)|openssl(1)>.
86 When creating new PKCS#8 containers, use a given number of iterations on
87 the password in deriving the encryption key for the PKCS#8 output.
88 High values increase the time required to brute-force a PKCS#8 container.
92 PKCS#8 keys generated or input are normally PKCS#8 EncryptedPrivateKeyInfo
93 structures using an appropriate password based encryption algorithm. With
94 this option an unencrypted PrivateKeyInfo structure is expected or output.
95 This option does not encrypt private keys at all and should only be used
96 when absolutely necessary. Certain software such as some versions of Java
97 code signing software used unencrypted private keys.
101 This option generates RSA private keys in a broken format that some software
102 uses. Specifically the private key should be enclosed in a OCTET STRING
103 but some software just includes the structure itself without the
104 surrounding OCTET STRING.
108 This option generates DSA keys in a broken format. The DSA parameters are
109 embedded inside the PrivateKey structure. In this form the OCTET STRING
110 contains an ASN1 SEQUENCE consisting of two structures: a SEQUENCE containing
111 the parameters and an ASN1 INTEGER containing the private key.
115 This option generates DSA keys in a broken format compatible with Netscape
116 private key databases. The PrivateKey contains a SEQUENCE consisting of
117 the public and private keys respectively.
121 This option enables the use of PKCS#5 v2.0 algorithms. Normally PKCS#8
122 private keys are encrypted with the password based encryption algorithm
123 called B<pbeWithMD5AndDES-CBC> this uses 56 bit DES encryption but it
124 was the strongest encryption algorithm supported in PKCS#5 v1.5. Using
125 the B<-v2> option PKCS#5 v2.0 algorithms are used which can use any
126 encryption algorithm such as 168 bit triple DES or 128 bit RC2 however
127 not many implementations support PKCS#5 v2.0 yet. If you are just using
128 private keys with OpenSSL then this doesn't matter.
130 The B<alg> argument is the encryption algorithm to use, valid values include
131 B<des>, B<des3> and B<rc2>. It is recommended that B<des3> is used.
135 This option sets the PRF algorithm to use with PKCS#5 v2.0. A typical value
136 values would be B<hmacWithSHA256>. If this option isn't set then the default
137 for the cipher is used or B<hmacWithSHA1> if there is no default.
141 This option specifies a PKCS#5 v1.5 or PKCS#12 algorithm to use. A complete
142 list of possible algorithms is included below.
146 specifying an engine (by its unique B<id> string) will cause B<pkcs8>
147 to attempt to obtain a functional reference to the specified engine,
148 thus initialising it if needed. The engine will then be set as the default
149 for all available algorithms.
153 uses the B<scrypt> algorithm for private key encryption using default
154 parameters: currently N=1024, r=8 and p=16 and AES in CBC mode with a 256 bit
155 key. These parameters can be modified using the B<-scrypt_N>, B<-scrypt_r>,
156 B<-scrypt_p> and B<-v2> options.
158 B<-scrypt_N N> B<-scrypt_r r> B<-scrypt_p p>
160 sets the scrypt B<N>, B<r> or B<p> parameters.
166 The encrypted form of a PEM encode PKCS#8 files uses the following
169 -----BEGIN ENCRYPTED PRIVATE KEY-----
170 -----END ENCRYPTED PRIVATE KEY-----
172 The unencrypted form uses:
174 -----BEGIN PRIVATE KEY-----
175 -----END PRIVATE KEY-----
177 Private keys encrypted using PKCS#5 v2.0 algorithms and high iteration
178 counts are more secure that those encrypted using the traditional
179 SSLeay compatible formats. So if additional security is considered
180 important the keys should be converted.
182 The default encryption is only 56 bits because this is the encryption
183 that most current implementations of PKCS#8 will support.
185 Some software may use PKCS#12 password based encryption algorithms
186 with PKCS#8 format private keys: these are handled automatically
187 but there is no option to produce them.
189 It is possible to write out DER encoded encrypted private keys in
190 PKCS#8 format because the encryption details are included at an ASN1
191 level whereas the traditional format includes them at a PEM level.
193 =head1 PKCS#5 v1.5 and PKCS#12 algorithms.
195 Various algorithms can be used with the B<-v1> command line option,
196 including PKCS#5 v1.5 and PKCS#12. These are described in more detail
201 =item B<PBE-MD2-DES PBE-MD5-DES>
203 These algorithms were included in the original PKCS#5 v1.5 specification.
204 They only offer 56 bits of protection since they both use DES.
206 =item B<PBE-SHA1-RC2-64 PBE-MD2-RC2-64 PBE-MD5-RC2-64 PBE-SHA1-DES>
208 These algorithms are not mentioned in the original PKCS#5 v1.5 specification
209 but they use the same key derivation algorithm and are supported by some
210 software. They are mentioned in PKCS#5 v2.0. They use either 64 bit RC2 or
213 =item B<PBE-SHA1-RC4-128 PBE-SHA1-RC4-40 PBE-SHA1-3DES PBE-SHA1-2DES PBE-SHA1-RC2-128 PBE-SHA1-RC2-40>
215 These algorithms use the PKCS#12 password based encryption algorithm and
216 allow strong encryption algorithms like triple DES or 128 bit RC2 to be used.
222 Convert a private from traditional to PKCS#5 v2.0 format using triple
225 openssl pkcs8 -in key.pem -topk8 -v2 des3 -out enckey.pem
227 Convert a private from traditional to PKCS#5 v2.0 format using AES with
228 256 bits in CBC mode and B<hmacWithSHA256> PRF:
230 openssl pkcs8 -in key.pem -topk8 -v2 aes-256-cbc -v2prf hmacWithSHA256 -out enckey.pem
232 Convert a private key to PKCS#8 using a PKCS#5 1.5 compatible algorithm
235 openssl pkcs8 -in key.pem -topk8 -out enckey.pem
237 Convert a private key to PKCS#8 using a PKCS#12 compatible algorithm
240 openssl pkcs8 -in key.pem -topk8 -out enckey.pem -v1 PBE-SHA1-3DES
242 Read a DER unencrypted PKCS#8 format private key:
244 openssl pkcs8 -inform DER -nocrypt -in key.der -out key.pem
246 Convert a private key from any PKCS#8 format to traditional format:
248 openssl pkcs8 -in pk8.pem -out key.pem
250 Convert a private key to PKCS#8 format, encrypting with AES-256 and with
251 one million iterations of the password:
253 openssl pkcs8 -in raw.pem -topk8 -v2 aes-256-cbc -iter 1000000 -out pk8.pem
257 Test vectors from this PKCS#5 v2.0 implementation were posted to the
258 pkcs-tng mailing list using triple DES, DES and RC2 with high iteration
259 counts, several people confirmed that they could decrypt the private
260 keys produced and Therefore it can be assumed that the PKCS#5 v2.0
261 implementation is reasonably accurate at least as far as these
262 algorithms are concerned.
264 The format of PKCS#8 DSA (and other) private keys is not well documented:
265 it is hidden away in PKCS#11 v2.01, section 11.9. OpenSSL's default DSA
266 PKCS#8 private key format complies with this standard.
270 There should be an option that prints out the encryption algorithm
271 in use and other details such as the iteration count.
273 PKCS#8 using triple DES and PKCS#5 v2.0 should be the default private
274 key format for OpenSSL: for compatibility several of the utilities use
275 the old format at present.
279 L<dsa(1)|dsa(1)>, L<rsa(1)|rsa(1)>, L<genrsa(1)|genrsa(1)>,
280 L<gendsa(1)|gendsa(1)>
284 The B<-iter> option was added to OpenSSL 1.1.0.