man > openssl-pkcs8(1)

OPENSSL-PKCS8(1SSL)                            OpenSSL                           OPENSSL-PKCS8(1SSL)

NAME
       openssl-pkcs8 - PKCS#8 format private key conversion command

SYNOPSIS
       openssl pkcs8 [-help] [-topk8] [-inform DER|PEM] [-outform DER|PEM] [-in filename] [-passin
       arg] [-out filename] [-passout arg] [-iter count] [-noiter] [-nocrypt] [-traditional] [-v2
       alg] [-v2prf alg] [-v1 alg] [-scrypt] [-scrypt_N N] [-scrypt_r r] [-scrypt_p p] [-rand files]
       [-writerand file] [-engine id] [-provider name] [-provider-path path] [-propquery propq]

DESCRIPTION
       This command processes private keys in PKCS#8 format. It can handle both unencrypted PKCS#8
       PrivateKeyInfo format and EncryptedPrivateKeyInfo format with a variety of PKCS#5 (v1.5 and
       v2.0) and PKCS#12 algorithms.

OPTIONS
       -help
           Print out a usage message.

       -topk8
           Normally  a  PKCS#8 private key is expected on input and a private key will be written to
           the output file. With the -topk8 option the situation is reversed: it reads a private key
           and writes a PKCS#8 format key.

       -inform DER|PEM, -outform DER|PEM
           The input and formats; the default is PEM.  See openssl-format-options(1) for details.

           If a key is being converted from PKCS#8 form (i.e. the -topk8 option is  not  used)  then
           the  input file must be in PKCS#8 format. An encrypted key is expected unless -nocrypt is
           included.

           If -topk8 is not used and PEM mode is set the output file will be an unencrypted  private
           key  in  PKCS#8  format.  If  the  -traditional  option is used then a traditional format
           private key is written instead.

           If -topk8 is not used and DER mode is set the output file will be an unencrypted  private
           key in traditional DER format.

           If  -topk8  is  used  then  any supported private key can be used for the input file in a
           format specified by -inform. The output file will be encrypted PKCS#8  format  using  the
           specified encryption parameters unless -nocrypt is included.

       -traditional
           When  this  option  is  present  and  -topk8  is  not a traditional format private key is
           written.

       -in filename
           This specifies the input filename to read a key from or standard input if this option  is
           not specified. If the key is encrypted a pass phrase will be prompted for.

       -passin arg, -passout arg
           The password source for the input and output file.  For more information about the format
           of arg see openssl-passphrase-options(1).

       -out filename
           This  specifies  the  output filename to write a key to or standard output by default. If
           any encryption options are set then a pass  phrase  will  be  prompted  for.  The  output
           filename should not be the same as the input filename.

       -iter count
           When  creating new PKCS#8 containers, use a given number of iterations on the password in
           deriving the encryption key for  the  PKCS#8  output.   High  values  increase  the  time
           required to brute-force a PKCS#8 container.

       -noiter
           When creating new PKCS#8 containers, use 1 as iteration count.

       -nocrypt
           PKCS#8  keys  generated  or  input are normally PKCS#8 EncryptedPrivateKeyInfo structures
           using an appropriate password based encryption algorithm. With this option an unencrypted
           PrivateKeyInfo structure is expected or output.  This option  does  not  encrypt  private
           keys  at  all and should only be used when absolutely necessary. Certain software such as
           some versions of Java code signing software used unencrypted private keys.

       -v2 alg
           This option sets the PKCS#5 v2.0 algorithm.

           The alg argument is the encryption algorithm to use, valid values include aes128,  aes256
           and des3. If this option isn't specified then aes256 is used.

       -v2prf alg
           This  option  sets the PRF algorithm to use with PKCS#5 v2.0. A typical value value would
           be hmacWithSHA256. If this option isn't set then the default for the cipher  is  used  or
           hmacWithSHA256 if there is no default.

           Some  implementations  may  not  support  custom  PRF  algorithms  and  may  require  the
           hmacWithSHA1 option to work.

       -v1 alg
           This option indicates a PKCS#5 v1.5 or PKCS#12 algorithm  should  be  used.   Some  older
           implementations  may  not  support  PKCS#5  v2.0  and  may  require  this option.  If not
           specified PKCS#5 v2.0 form is used.

       -scrypt
           Uses the scrypt algorithm for private key encryption using default parameters:  currently
           N=16384,  r=8  and  p=1  and  AES in CBC mode with a 256 bit key. These parameters can be
           modified using the -scrypt_N, -scrypt_r, -scrypt_p and -v2 options.

       -scrypt_N N, -scrypt_r r, -scrypt_p p
           Sets the scrypt N, r or p parameters.

       -rand files, -writerand file
           See "Random State Options" in openssl(1) for details.

       -engine id
           See "Engine Options" in openssl(1).  This option is deprecated.

       -provider name
       -provider-path path
       -propquery propq
           See "Provider Options" in openssl(1), provider(7), and property(7).

NOTES
       By default, when converting a key to PKCS#8 format, PKCS#5 v2.0 using 256 bit AES  with  HMAC
       and SHA256 is used.

       Some  older  implementations  do  not support PKCS#5 v2.0 format and require the older PKCS#5
       v1.5 form instead, possibly also requiring insecure weak encryption algorithms such as 56 bit
       DES.

       Private keys encrypted using PKCS#5 v2.0 algorithms and high iteration counts are more secure
       that those encrypted using the  traditional  SSLeay  compatible  formats.  So  if  additional
       security is considered important the keys should be converted.

       It  is  possible to write out DER encoded encrypted private keys in PKCS#8 format because the
       encryption details are included at an ASN1 level whereas the traditional format includes them
       at a PEM level.

PKCS#5 V1.5 AND PKCS#12 ALGORITHMS
       Various algorithms can be used with the -v1 command line option, including  PKCS#5  v1.5  and
       PKCS#12. These are described in more detail below.

       PBE-MD2-DES PBE-MD5-DES
           These  algorithms  were  included  in  the original PKCS#5 v1.5 specification.  They only
           offer 56 bits of protection since they both use DES.

       PBE-SHA1-RC2-64, PBE-MD2-RC2-64, PBE-MD5-RC2-64, PBE-SHA1-DES
           These algorithms are not mentioned in the original PKCS#5 v1.5 specification but they use
           the same key derivation algorithm and are supported by some software. They are  mentioned
           in PKCS#5 v2.0. They use either 64 bit RC2 or 56 bit DES.

       PBE-SHA1-RC4-128, PBE-SHA1-RC4-40, PBE-SHA1-3DES, PBE-SHA1-2DES, PBE-SHA1-RC2-128,
       PBE-SHA1-RC2-40
           These  algorithms  use  the  PKCS#12 password based encryption algorithm and allow strong
           encryption algorithms like triple DES or 128 bit RC2 to be used.

EXAMPLES
       Convert a private key to PKCS#8 format using default parameters (AES with  256  bit  key  and
       hmacWithSHA256):

        openssl pkcs8 -in key.pem -topk8 -out enckey.pem

       Convert a private key to PKCS#8 unencrypted format:

        openssl pkcs8 -in key.pem -topk8 -nocrypt -out enckey.pem

       Convert a private key to PKCS#5 v2.0 format using triple DES:

        openssl pkcs8 -in key.pem -topk8 -v2 des3 -out enckey.pem

       Convert  a  private  key  to  PKCS#5  v2.0  format  using  AES  with 256 bits in CBC mode and
       hmacWithSHA512 PRF:

        openssl pkcs8 -in key.pem -topk8 -v2 aes-256-cbc -v2prf hmacWithSHA512 -out enckey.pem

       Convert a private key to PKCS#8 using a PKCS#5 1.5 compatible algorithm (DES):

        openssl pkcs8 -in key.pem -topk8 -v1 PBE-MD5-DES -out enckey.pem

       Convert a private key to PKCS#8 using a PKCS#12 compatible algorithm (3DES):

        openssl pkcs8 -in key.pem -topk8 -out enckey.pem -v1 PBE-SHA1-3DES

       Read a DER unencrypted PKCS#8 format private key:

        openssl pkcs8 -inform DER -nocrypt -in key.der -out key.pem

       Convert a private key from any PKCS#8 encrypted format to traditional format:

        openssl pkcs8 -in pk8.pem -traditional -out key.pem

       Convert a private key to  PKCS#8  format,  encrypting  with  AES-256  and  with  one  million
       iterations of the password:

        openssl pkcs8 -in key.pem -topk8 -v2 aes-256-cbc -iter 1000000 -out pk8.pem

STANDARDS
       Test  vectors  from  this PKCS#5 v2.0 implementation were posted to the pkcs-tng mailing list
       using triple DES, DES and RC2 with high iteration counts, several people confirmed that  they
       could decrypt the private keys produced and therefore, it can be assumed that the PKCS#5 v2.0
       implementation is reasonably accurate at least as far as these algorithms are concerned.

       The  format  of PKCS#8 DSA (and other) private keys is not well documented: it is hidden away
       in PKCS#11 v2.01, section 11.9. OpenSSL's default DSA PKCS#8 private key format complies with
       this standard.

BUGS
       There should be an option that prints out the encryption algorithm in use and  other  details
       such as the iteration count.

SEE ALSO
       openssl(1), openssl-dsa(1), openssl-rsa(1), openssl-genrsa(1), openssl-gendsa(1)

HISTORY
       The -iter option was added in OpenSSL 1.1.0.

       The -engine option was deprecated in OpenSSL 3.0.

COPYRIGHT
       Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.

       Licensed  under  the Apache License 2.0 (the "License").  You may not use this file except in
       compliance with the License.  You can obtain a  copy  in  the  file  LICENSE  in  the  source
       distribution or at <https://www.openssl.org/source/license.html>.

3.0.13                                       2026-07-29                          OPENSSL-PKCS8(1SSL)