{ "mode": "man", "parameter": "openssl-pkcs8", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/openssl-pkcs8/1/json", "generated": "2026-06-16T00:39:06Z", "synopsis": "openssl pkcs8 [-help] [-topk8] [-inform DER|PEM] [-outform DER|PEM] [-in filename] [-passin\narg] [-out filename] [-passout arg] [-iter count] [-noiter] [-nocrypt] [-traditional] [-v2\nalg] [-v2prf alg] [-v1 alg] [-scrypt] [-scryptN N] [-scryptr r] [-scryptp p] [-rand files]\n[-writerand file] [-engine id] [-provider name] [-provider-path path] [-propquery propq]", "sections": { "NAME": { "content": "openssl-pkcs8 - PKCS#8 format private key conversion command\n", "subsections": [] }, "SYNOPSIS": { "content": "openssl pkcs8 [-help] [-topk8] [-inform DER|PEM] [-outform DER|PEM] [-in filename] [-passin\narg] [-out filename] [-passout arg] [-iter count] [-noiter] [-nocrypt] [-traditional] [-v2\nalg] [-v2prf alg] [-v1 alg] [-scrypt] [-scryptN N] [-scryptr r] [-scryptp p] [-rand files]\n[-writerand file] [-engine id] [-provider name] [-provider-path path] [-propquery propq]\n", "subsections": [] }, "DESCRIPTION": { "content": "This command processes private keys in PKCS#8 format. It can handle both unencrypted PKCS#8\nPrivateKeyInfo format and EncryptedPrivateKeyInfo format with a variety of PKCS#5 (v1.5 and\nv2.0) and PKCS#12 algorithms.\n", "subsections": [] }, "OPTIONS": { "content": "", "subsections": [ { "name": "-help", "content": "Print out a usage message.\n" }, { "name": "-topk8", "content": "Normally a PKCS#8 private key is expected on input and a private key will be written to\nthe output file. With the -topk8 option the situation is reversed: it reads a private key\nand writes a PKCS#8 format key.\n" }, { "name": "-inform -outform", "content": "The input and formats; the default is PEM. See openssl-format-options(1) for details.\n\nIf a key is being converted from PKCS#8 form (i.e. the -topk8 option is not used) then\nthe input file must be in PKCS#8 format. An encrypted key is expected unless -nocrypt is\nincluded.\n\nIf -topk8 is not used and PEM mode is set the output file will be an unencrypted private\nkey in PKCS#8 format. If the -traditional option is used then a traditional format\nprivate key is written instead.\n\nIf -topk8 is not used and DER mode is set the output file will be an unencrypted private\nkey in traditional DER format.\n\nIf -topk8 is used then any supported private key can be used for the input file in a\nformat specified by -inform. The output file will be encrypted PKCS#8 format using the\nspecified encryption parameters unless -nocrypt is included.\n" }, { "name": "-traditional", "content": "When this option is present and -topk8 is not a traditional format private key is\nwritten.\n" }, { "name": "-in", "content": "This specifies the input filename to read a key from or standard input if this option is\nnot specified. If the key is encrypted a pass phrase will be prompted for.\n" }, { "name": "-passin -passout", "content": "The password source for the input and output file. For more information about the format\nof arg see openssl-passphrase-options(1).\n" }, { "name": "-out", "content": "This specifies the output filename to write a key to or standard output by default. If\nany encryption options are set then a pass phrase will be prompted for. The output\nfilename should not be the same as the input filename.\n" }, { "name": "-iter", "content": "When creating new PKCS#8 containers, use a given number of iterations on the password in\nderiving the encryption key for the PKCS#8 output. High values increase the time\nrequired to brute-force a PKCS#8 container.\n" }, { "name": "-noiter", "content": "When creating new PKCS#8 containers, use 1 as iteration count.\n" }, { "name": "-nocrypt", "content": "PKCS#8 keys generated or input are normally PKCS#8 EncryptedPrivateKeyInfo structures\nusing an appropriate password based encryption algorithm. With this option an unencrypted\nPrivateKeyInfo structure is expected or output. This option does not encrypt private\nkeys at all and should only be used when absolutely necessary. Certain software such as\nsome versions of Java code signing software used unencrypted private keys.\n" }, { "name": "-v2", "content": "This option sets the PKCS#5 v2.0 algorithm.\n\nThe alg argument is the encryption algorithm to use, valid values include aes128, aes256\nand des3. If this option isn't specified then aes256 is used.\n" }, { "name": "-v2prf", "content": "This option sets the PRF algorithm to use with PKCS#5 v2.0. A typical value value would\nbe hmacWithSHA256. If this option isn't set then the default for the cipher is used or\nhmacWithSHA256 if there is no default.\n\nSome implementations may not support custom PRF algorithms and may require the\nhmacWithSHA1 option to work.\n" }, { "name": "-v1", "content": "This option indicates a PKCS#5 v1.5 or PKCS#12 algorithm should be used. Some older\nimplementations may not support PKCS#5 v2.0 and may require this option. If not\nspecified PKCS#5 v2.0 form is used.\n" }, { "name": "-scrypt", "content": "Uses the scrypt algorithm for private key encryption using default parameters: currently\nN=16384, r=8 and p=1 and AES in CBC mode with a 256 bit key. These parameters can be\nmodified using the -scryptN, -scryptr, -scryptp and -v2 options.\n" }, { "name": "-scrypt -scrypt -scrypt", "content": "Sets the scrypt N, r or p parameters.\n" }, { "name": "-rand -writerand", "content": "See \"Random State Options\" in openssl(1) for details.\n" }, { "name": "-engine", "content": "See \"Engine Options\" in openssl(1). This option is deprecated.\n" }, { "name": "-provider", "content": "" }, { "name": "-provider-path", "content": "" }, { "name": "-propquery", "content": "See \"Provider Options\" in openssl(1), provider(7), and property(7).\n" } ] }, "NOTES": { "content": "By default, when converting a key to PKCS#8 format, PKCS#5 v2.0 using 256 bit AES with HMAC\nand SHA256 is used.\n\nSome older implementations do not support PKCS#5 v2.0 format and require the older PKCS#5\nv1.5 form instead, possibly also requiring insecure weak encryption algorithms such as 56 bit\nDES.\n\nPrivate keys encrypted using PKCS#5 v2.0 algorithms and high iteration counts are more secure\nthat those encrypted using the traditional SSLeay compatible formats. So if additional\nsecurity is considered important the keys should be converted.\n\nIt is possible to write out DER encoded encrypted private keys in PKCS#8 format because the\nencryption details are included at an ASN1 level whereas the traditional format includes them\nat a PEM level.\n", "subsections": [ { "name": "PKCS#5 V1.5 AND PKCS#12 ALGORITHMS", "content": "Various algorithms can be used with the -v1 command line option, including PKCS#5 v1.5 and\nPKCS#12. These are described in more detail below.\n\nPBE-MD2-DES PBE-MD5-DES\nThese algorithms were included in the original PKCS#5 v1.5 specification. They only\noffer 56 bits of protection since they both use DES.\n\nPBE-SHA1-RC2-64, PBE-MD2-RC2-64, PBE-MD5-RC2-64, PBE-SHA1-DES\nThese algorithms are not mentioned in the original PKCS#5 v1.5 specification but they use\nthe same key derivation algorithm and are supported by some software. They are mentioned\nin PKCS#5 v2.0. They use either 64 bit RC2 or 56 bit DES.\n\nPBE-SHA1-RC4-128, PBE-SHA1-RC4-40, PBE-SHA1-3DES, PBE-SHA1-2DES, PBE-SHA1-RC2-128,\nPBE-SHA1-RC2-40\nThese algorithms use the PKCS#12 password based encryption algorithm and allow strong\nencryption algorithms like triple DES or 128 bit RC2 to be used.\n" } ] }, "EXAMPLES": { "content": "Convert a private key to PKCS#8 format using default parameters (AES with 256 bit key and\nhmacWithSHA256):\n\nopenssl pkcs8 -in key.pem -topk8 -out enckey.pem\n\nConvert a private key to PKCS#8 unencrypted format:\n\nopenssl pkcs8 -in key.pem -topk8 -nocrypt -out enckey.pem\n\nConvert a private key to PKCS#5 v2.0 format using triple DES:\n\nopenssl pkcs8 -in key.pem -topk8 -v2 des3 -out enckey.pem\n\nConvert a private key to PKCS#5 v2.0 format using AES with 256 bits in CBC mode and\nhmacWithSHA512 PRF:\n\nopenssl pkcs8 -in key.pem -topk8 -v2 aes-256-cbc -v2prf hmacWithSHA512 -out enckey.pem\n\nConvert a private key to PKCS#8 using a PKCS#5 1.5 compatible algorithm (DES):\n\nopenssl pkcs8 -in key.pem -topk8 -v1 PBE-MD5-DES -out enckey.pem\n\nConvert a private key to PKCS#8 using a PKCS#12 compatible algorithm (3DES):\n\nopenssl pkcs8 -in key.pem -topk8 -out enckey.pem -v1 PBE-SHA1-3DES\n\nRead a DER unencrypted PKCS#8 format private key:\n\nopenssl pkcs8 -inform DER -nocrypt -in key.der -out key.pem\n\nConvert a private key from any PKCS#8 encrypted format to traditional format:\n\nopenssl pkcs8 -in pk8.pem -traditional -out key.pem\n\nConvert a private key to PKCS#8 format, encrypting with AES-256 and with one million\niterations of the password:\n\nopenssl pkcs8 -in key.pem -topk8 -v2 aes-256-cbc -iter 1000000 -out pk8.pem\n", "subsections": [] }, "STANDARDS": { "content": "Test vectors from this PKCS#5 v2.0 implementation were posted to the pkcs-tng mailing list\nusing triple DES, DES and RC2 with high iteration counts, several people confirmed that they\ncould decrypt the private keys produced and therefore, it can be assumed that the PKCS#5 v2.0\nimplementation is reasonably accurate at least as far as these algorithms are concerned.\n\nThe format of PKCS#8 DSA (and other) private keys is not well documented: it is hidden away\nin PKCS#11 v2.01, section 11.9. OpenSSL's default DSA PKCS#8 private key format complies with\nthis standard.\n", "subsections": [] }, "BUGS": { "content": "There should be an option that prints out the encryption algorithm in use and other details\nsuch as the iteration count.\n", "subsections": [] }, "SEE ALSO": { "content": "openssl(1), openssl-dsa(1), openssl-rsa(1), openssl-genrsa(1), openssl-gendsa(1)\n", "subsections": [] }, "HISTORY": { "content": "The -iter option was added in OpenSSL 1.1.0.\n\nThe -engine option was deprecated in OpenSSL 3.0.\n", "subsections": [] }, "COPYRIGHT": { "content": "Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.\n\nLicensed under the Apache License 2.0 (the \"License\"). You may not use this file except in\ncompliance with the License. You can obtain a copy in the file LICENSE in the source\ndistribution or at .\n\n\n\n3.0.2 2026-06-02 OPENSSL-PKCS8(1SSL)", "subsections": [] } }, "summary": "openssl-pkcs8 - PKCS#8 format private key conversion command", "flags": [ { "flag": "", "long": null, "arg": null, "description": "Print out a usage message." }, { "flag": "", "long": null, "arg": null, "description": "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." }, { "flag": "", "long": null, "arg": null, "description": "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." }, { "flag": "", "long": null, "arg": null, "description": "When this option is present and -topk8 is not a traditional format private key is written." }, { "flag": "", "long": null, "arg": null, "description": "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." }, { "flag": "", "long": null, "arg": null, "description": "The password source for the input and output file. For more information about the format of arg see openssl-passphrase-options(1)." }, { "flag": "", "long": null, "arg": null, "description": "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." }, { "flag": "", "long": null, "arg": null, "description": "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." }, { "flag": "", "long": null, "arg": null, "description": "When creating new PKCS#8 containers, use 1 as iteration count." }, { "flag": "", "long": null, "arg": null, "description": "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." }, { "flag": "", "long": null, "arg": null, "description": "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." }, { "flag": "", "long": null, "arg": null, "description": "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." }, { "flag": "", "long": null, "arg": null, "description": "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." }, { "flag": "", "long": null, "arg": null, "description": "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 -scryptN, -scryptr, -scryptp and -v2 options." }, { "flag": "", "long": null, "arg": null, "description": "Sets the scrypt N, r or p parameters." }, { "flag": "", "long": null, "arg": null, "description": "See \"Random State Options\" in openssl(1) for details." }, { "flag": "", "long": null, "arg": null, "description": "See \"Engine Options\" in openssl(1). This option is deprecated." }, { "flag": "", "long": null, "arg": null, "description": "" }, { "flag": "", "long": null, "arg": null, "description": "" }, { "flag": "", "long": null, "arg": null, "description": "See \"Provider Options\" in openssl(1), provider(7), and property(7)." } ], "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" ], "see_also": [ { "name": "openssl", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/openssl/1/json" }, { "name": "openssl-dsa", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/openssl-dsa/1/json" }, { "name": "openssl-rsa", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/openssl-rsa/1/json" }, { "name": "openssl-genrsa", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/openssl-genrsa/1/json" }, { "name": "openssl-gendsa", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/openssl-gendsa/1/json" } ] }