DESCRIPTIONThe 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.
COMMAND OPTIONS
-inform DER|NET|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. The NET form
is a format is described in the NOTES section.
-outform DER|NET|PEM This specifies the output format, the options have the same
meaning 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) .
-sgckey use the modified NET algorithm used with some versions of
Microsoft IIS and SGC keys.
-des|-des3|-idea These options encrypt the private key with the DES, triple
DES, or the IDEA ciphers respectively 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.
-engine id specifying an engine (by it's unique id string) will cause
req 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.
NOTESThe PEM private key format uses the header and footer lines:
The PEM public key format uses the header and footer lines:
-----BEGIN PUBLIC KEY-----
-----END PUBLIC KEY-----
The NET form is a format compatible with older Netscape servers
and Microsoft IIS .key files, this uses unsalted RC4 for its encryption.
It is not very secure and so should only be used when necessary.
Some newer version of IIS have additional data in the exported
.key files. To use these with the utility, view the file with a
binary editor and look for the string "private-key", then trace
back to the byte sequence 0x30, 0x82 (this is an ASN1 SEQUENCE).
Copy all the data from this point onwards to another file and use
that as the input to the rsa utility with the -inform NET option.
If you get an error after entering the password try the -sgckey
option.
EXAMPLESTo 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
RestrictionsThe command line password arguments don't currently work with
NET format.
There should be an option that automatically handles .key
files, without having to manually edit them.
HP Open Source Security for OpenVMS Volume 2:... 
OpenSSL Command Line Interface (CLI) Reference
