RSA(1) OpenSSL RSA(1)NAME
rsa - RSA key processing tool
openssl rsa [-inform PEM⎪NET⎪DER] [-outform PEM⎪NET⎪DER] [-in filename]
[-passin arg] [-out filename] [-passout arg] [-sgckey] [-des] [-des3]
[-idea] [-text] [-noout] [-modulus] [-check] [-pubin] [-pubout]
The rsa command processes RSA keys. They can be converted between vari‐
ous 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
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 Subject‐
PublicKeyInfo format. The PEM form is the default format: it con‐
sists 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 sec‐
This specifies the output format, the options have the same meaning
as the -inform option.
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.
the input file password source. For more information about the for‐
mat of arg see the PASS PHRASE ARGUMENTS section in openssl(1).
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 file‐
name should not be the same as the input filename.
the output file password source. For more information about the
format of arg see the PASS PHRASE ARGUMENTS section in openssl(1).
use the modified NET algorithm used with some versions of Microsoft
IIS and SGC keys.
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.
prints out the various public or private key components in plain
text in addition to the encoded version.
this option prevents output of the encoded version of the key.
this option prints out the value of the modulus of the key.
this option checks the consistency of an RSA private key.
by default a private key is read from the input file: with this
option a public key is read instead.
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.
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.
The PEM private key format uses the header and footer lines:
-----BEGINRSA PRIVATE KEY-----
-----ENDRSA PRIVATE KEY-----
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 Mi‐
crosoft 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 edi‐
tor 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.
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
The command line password arguments don't currently work with NET for‐
There should be an option that automatically handles .key files, with‐
out having to manually edit them.
SEE ALSOpkcs8(1), dsa(1), genrsa(1), gendsa(1)0.9.8k 2009-05-20 RSA(1)