openssl-rsa, rsa - RSA key processing tool
openssl rsa [-help] [-inform PEM|DER] [-outform
  PEM|DER] [-in filename] [-passin arg] [-out filename]
  [-passout arg] [-aes128] [-aes192] [-aes256]
  [-aria128] [-aria192] [-aria256] [-camellia128]
  [-camellia192] [-camellia256] [-des] [-des3]
  [-idea] [-text] [-noout] [-modulus]
  [-check] [-pubin] [-pubout] [-RSAPublicKey_in]
  [-RSAPublicKey_out] [-engine id]
The rsa command processes RSA keys. They can be converted between various
  forms and their components printed out. Note this command uses the
  traditional SSLeay compatible format for private key encryption: newer
  applications should use the more secure PKCS#8 format using the pkcs8
  utility.
  - -help
- Print out a usage message.
- -inform DER|PEM
- This specifies the input format. The DER option uses an ASN1 DER
      encoded form compatible with the PKCS#1 RSAPrivateKey or
      SubjectPublicKeyInfo format. The PEM form is the default format: it
      consists of the DER format base64 encoded with additional header
      and footer lines. On input PKCS#8 format private keys are also
    accepted.
- -outform DER|PEM
- This specifies the output format, the options have the same meaning and
      default as the -inform option.
- -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
- The input file password source. For more information about the format of
      arg see the PASS PHRASE ARGUMENTS section in
      openssl(1).
- -out filename
- This specifies the output filename to write a key to or standard output if
      this option is not specified. 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.
- -passout password
- The output file password source. For more information about the format of
      arg see the PASS PHRASE ARGUMENTS section in
      openssl(1).
- -aes128, -aes192, -aes256, -aria128,
    -aria192, -aria256, -camellia128, -camellia192,
    -camellia256, -des, -des3, -idea
- These options encrypt the private key with the specified cipher before
      outputting it. A pass phrase is prompted for. If none of these options is
      specified the key is written in plain text. This means that using the
      rsa utility to read in an encrypted key with no encryption option
      can be used to remove the pass phrase from a key, or by setting the
      encryption options it can be use to add or change the pass phrase. These
      options can only be used with PEM format output files.
- -text
- Prints out the various public or private key components in plain text in
      addition to the encoded version.
- -noout
- This option prevents output of the encoded version of the key.
- -modulus
- This option prints out the value of the modulus of the key.
- -check
- This option checks the consistency of an RSA private key.
- -pubin
- By default a private key is read from the input file: with this option a
      public key is read instead.
- -pubout
- By default a private key is output: with this option a public key will be
      output instead. This option is automatically set if the input is a public
      key.
- -RSAPublicKey_in, -RSAPublicKey_out
- Like -pubin and -pubout except RSAPublicKey format is
      used instead.
- -engine id
- Specifying an engine (by its unique id string) will cause
      rsa to attempt to obtain a functional reference to the specified
      engine, thus initialising it if needed. The engine will then be set as the
      default for all available algorithms.
The PEM private key format uses the header and footer lines:
 -----BEGIN RSA PRIVATE KEY-----
 -----END RSA PRIVATE KEY-----
The PEM public key format uses the header and footer lines:
 -----BEGIN PUBLIC KEY-----
 -----END PUBLIC KEY-----
The PEM RSAPublicKey format uses the header and footer
    lines:
 -----BEGIN RSA PUBLIC KEY-----
 -----END RSA PUBLIC KEY-----
To remove the pass phrase on an RSA private key:
 openssl rsa -in key.pem -out keyout.pem
To encrypt a private key using triple DES:
 openssl rsa -in key.pem -des3 -out keyout.pem
To convert a private key from PEM to DER format:
 openssl rsa -in key.pem -outform DER -out keyout.der
To print out the components of a private key to standard
  output:
 openssl rsa -in key.pem -text -noout
To just output the public part of a private key:
 openssl rsa -in key.pem -pubout -out pubkey.pem
Output the public part of a private key in RSAPublicKey
    format:
 openssl rsa -in key.pem -RSAPublicKey_out -out pubkey.pem
There should be an option that automatically handles .key files, without having
  to manually edit them.
pkcs8(1), dsa(1), genrsa(1), gendsa(1)
Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the OpenSSL license (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>.