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.
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 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.
NOTES
The 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.
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
BUGS
The 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.
