OPENSSL-PKCS8(1SSL)

📦
version 4.0.3 · 13 versions
, in ubuntu stonking

💖 openssl-pkcs8 💖

okay so bestie, this is openssl-pkcs8, the OpenSSL command that does the whole PKCS#8 format private key conversion thing. it's giving ✨ key glow-up ✨ and honestly? iconic. let's get into it 🫶

🌸 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] [-saltlen size]
[-rand files] [-writerand file] [-provider name] [-provider-path path]
[-provparam [name:]key=value] [-propquery propq]

🦋 DESCRIPTION 🦋

So like, this command processes private keys in PKCS#8 format. Periodt. 💅

It can handle both an unencrypted PKCS#8 PrivateKeyInfo format and the EncryptedPrivateKeyInfo format, with a whole variety of PKCS#5 (v1.5 and v2.0) and PKCS#12 algorithms. she's versatile, she's flexible, she contains multitudes 💜

✨ OPTIONS ✨

  • -help — prints out a usage message. classic. the little "what do i do" button 🎀
  • -topk8 — okay so normally a PKCS#8 private key is expected on input and a private key gets written to the output file. with the -topk8 option the whole situation is reversed: it reads a private key and writes a PKCS#8 format key. flip it and reverse it 🔥
  • -inform DER|PEM, -outform DER|PEM — the input and output formats; the default is PEM. go peep openssl-format-options(1) for the deets 💫
    • 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. no sneaking past this one bestie.
    • 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. old school cool 🕶️
  • -in filename — this specifies the input file to read a key from, or standard input if this option isn't specified. if the key is encrypted a pass phrase will be prompted for unless -passin is given. she will ask. be ready 🙈
  • -passin arg, -passout arg — the password source for the input and output file. for more info about the format of arg see openssl-passphrase-options(1). 🔐
  • -out filename — this specifies the output file to write a key to, or standard output by default. heads up: the output filename can be the same as the input filename, which leads to replacing the file contents. note that file I/O is not atomic. the output file is truncated and then written. 😭
    • if any encryption options are set and -passout is not given then a pass phrase will be prompted for. when password input is interrupted, the output file is not touched. safe. 🫶
  • -iter count — when creating new PKCS#8 containers, use a given number of iterations on the password when deriving the encryption key for the PKCS#8 output. high values increase the time required to brute-force a PKCS#8 container. more iterations = more slay, but also more waiting ⏳
  • -noiter — when creating new PKCS#8 containers, use 1 as the iteration count. literally one. that's it. that's the whole vibe 💀
  • -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.
⚠️ bestie. 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. so like… necessity only. not a vibe. but valid. 😭
  • -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. default queen 👑
  • -v2prf alg — this option sets the PRF algorithm to use with PKCS#5 v2.0. a typical valid 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. iykyk 🌈
  • -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. retro mode activated ✨
  • -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. fancy algorithm alert 🔥
  • -scrypt_N N, -scrypt_r r, -scrypt_p p — sets the scrypt N, r or p parameters. just tweak the knobs babe 🎛️
  • -saltlen — sets the length (in bytes) of the salt to use for the PBE algorithm. if this value isn't specified, the default for PBES2 is 16 (128 bits) and 8 (64 bits) for PBES1. ✨ a lil seasoning ✨
  • -rand files, -writerand file — see "Random State Options" in openssl(1) for details. randomness is important bestie 🎲
  • -provider name
  • -provider-path path
  • -provparam [name:]key=value
  • -propquery propq — see "Provider Options" in openssl(1), provider(7), and property(7). the provider squad 🫶

📝 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. that's the default slay. ✨

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. 💀 lowkey terrifying.

private keys encrypted using PKCS#5 v2.0 algorithms and high iteration counts are more secure than those encrypted using the traditional SSLeay compatible formats. so if additional security is considered important, the keys should be converted. do it bestie, protect your keys 🔐

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. baby encryption. cute but dangerous 😬
  • 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. now this is main character energy 🔥

🌈 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, and several people confirmed that they could decrypt the private keys produced. therefore, it can be assumed that the PKCS#5 v2.0 implementation is reasonably accurate at least as far as these algorithms are concerned. peer reviewed fr fr ✅

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. she follows the rules 💅

💀 BUGS 💀

there should be an option that prints out the encryption algorithm in use and other details such as the iteration count. currently? nope. not me waiting for that feature 😭

🔗 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. a classic.
  • the -engine option was removed in OpenSSL 4.0. rip to a real one 🪦

Copyright 2000-2026 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>.

and that's the whole page bestie!! 🫶 this was openssl-pkcs8 from the OpenSSL manual, version 4.0.3, dated 2026-09-29 💖 go convert some keys, stay encrypted, and remember: high iteration counts are self care ✨🔐👑

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