=pod

=head1 NAME

openssl-rsa,
rsa - RSA key processing tool

=head1 SYNOPSIS

B<openssl> B<rsa>
[B<-help>]
[B<-inform PEM|DER>]
[B<-outform PEM|DER>]
[B<-in filename>]
[B<-passin arg>]
[B<-out filename>]
[B<-passout arg>]
[B<-aes128>]
[B<-aes192>]
[B<-aes256>]
[B<-aria128>]
[B<-aria192>]
[B<-aria256>]
[B<-camellia128>]
[B<-camellia192>]
[B<-camellia256>]
[B<-des>]
[B<-des3>]
[B<-idea>]
[B<-text>]
[B<-noout>]
[B<-modulus>]
[B<-check>]
[B<-pubin>]
[B<-pubout>]
[B<-RSAPublicKey_in>]
[B<-RSAPublicKey_out>]
[B<-engine id>]

=head1 DESCRIPTION

The B<rsa> command processes RSA keys. They can be converted between various
forms and their components printed out. B<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 B<pkcs8>
utility.

=head1 OPTIONS

=over 4

=item B<-help>

Print out a usage message.

=item B<-inform DER|PEM>

This specifies the input format. The B<DER> option uses an ASN1 DER encoded
form compatible with the PKCS#1 RSAPrivateKey or SubjectPublicKeyInfo format.
The B<PEM> form is the default format: it consists of the B<DER> format base64
encoded with additional header and footer lines. On input PKCS#8 format private
keys are also accepted.

=item B<-outform DER|PEM>

This specifies the output format, the options have the same meaning and default
as the B<-inform> option.

=item B<-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.

=item B<-passin arg>

The input file password source. For more information about the format of B<arg>
see L<openssl(1)/Pass Phrase Options>.

=item B<-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 B<not> be the same as the input
filename.

=item B<-passout password>

The output file password source. For more information about the format of B<arg>
see L<openssl(1)/Pass Phrase Options>.

=item B<-aes128>, B<-aes192>, B<-aes256>, B<-aria128>, B<-aria192>, B<-aria256>, B<-camellia128>, B<-camellia192>, B<-camellia256>, B<-des>, B<-des3>, B<-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 B<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.

=item B<-text>

Prints out the various public or private key components in
plain text in addition to the encoded version.

=item B<-noout>

This option prevents output of the encoded version of the key.

=item B<-modulus>

This option prints out the value of the modulus of the key.

=item B<-check>

This option checks the consistency of an RSA private key.

=item B<-pubin>

By default a private key is read from the input file: with this
option a public key is read instead.

=item B<-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.

=item B<-RSAPublicKey_in>, B<-RSAPublicKey_out>

Like B<-pubin> and B<-pubout> except B<RSAPublicKey> format is used instead.

=item B<-engine id>

Specifying an engine (by its unique B<id> string) will cause B<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.

=back

=head1 NOTES

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 B<RSAPublicKey> format uses the header and footer lines:

 -----BEGIN RSA PUBLIC KEY-----
 -----END RSA PUBLIC KEY-----

=head1 EXAMPLES

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 B<RSAPublicKey> format:

 openssl rsa -in key.pem -RSAPublicKey_out -out pubkey.pem

=head1 BUGS

There should be an option that automatically handles .key files,
without having to manually edit them.

=head1 SEE ALSO

L<pkcs8(1)>, L<dsa(1)>, L<genrsa(1)>,
L<gendsa(1)>

=head1 COPYRIGHT

Copyright 2000-2021 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
L<https://www.openssl.org/source/license.html>.

=cut
