OpenSSL    
 Index |  openssl(1) |  ssl(3) |  crypto(3) |  HOWTO |  FIPS140 |  misc 
 
Title
FAQ
About
News
Documents
Source
Contribution
Support
Related

 

genpkey(1)



NAME

genpkey - generate a private key


SYNOPSIS

openssl genpkey [-out filename] [-outform PEM|DER] [-pass arg] [-cipher] [-engine id] [-paramfile file] [-algorithm alg] [-pkeyopt opt:value] [-genparam] [-text]


DESCRIPTION

The genpkey command generates a private key.


OPTIONS

-out filename

the output filename. If this argument is not specified then standard output is used.

-outform DER|PEM

This specifies the output format DER or PEM.

-pass arg

the output file password source. For more information about the format of arg see the PASS PHRASE ARGUMENTS section in openssl(1).

-cipher

This option encrypts the private key with the supplied cipher. Any algorithm name accepted by EVP_get_cipherbyname() is acceptable such as des3.

-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. If used this option should precede all other options.

-algorithm alg

public key algorithm to use such as RSA, DSA or DH. If used this option must precede any -pkeyopt options. The options -paramfile and -algorithm are mutually exclusive.

-pkeyopt opt:value

set the public key algorithm option opt to value. The precise set of options supported depends on the public key algorithm used and its implementation. See KEY GENERATION OPTIONS below for more details.

-genparam

generate a set of parameters instead of a private key. If used this option must precede and -algorithm, -paramfile or -pkeyopt options.

-paramfile filename

Some public key algorithms generate a private key based on a set of parameters. They can be supplied using this option. If this option is used the public key algorithm used is determined by the parameters. If used this option must precede and -pkeyopt options. The options -paramfile and -algorithm are mutually exclusive.

-text

Print an (unencrypted) text representation of private and public keys and parameters along with the PEM or DER structure.


KEY GENERATION OPTIONS

The options supported by each algorith and indeed each implementation of an algorithm can vary. The options for the OpenSSL implementations are detailed below.


RSA KEY GENERATION OPTIONS

rsa_keygen_bits:numbits

The number of bits in the generated key. If not specified 1024 is used.

rsa_keygen_pubexp:value

The RSA public exponent value. This can be a large decimal or hexadecimal value if preceded by 0x. Default value is 65537.


DSA PARAMETER GENERATION OPTIONS

dsa_paramgen_bits:numbits

The number of bits in the generated parameters. If not specified 1024 is used.

DH PARAMETER GENERATION OPTIONS

dh_paramgen_prime_len:numbits

The number of bits in the prime parameter p.

dh_paramgen_generator:value

The value to use for the generator g.

EC PARAMETER GENERATION OPTIONS

ec_paramgen_curve:curve

the EC curve to use.

NOTES

The use of the genpkey program is encouraged over the algorithm specific utilities because additional algorithm options and ENGINE provided algorithms can be used.

EXAMPLES

Generate an RSA private key using default parameters:

 openssl genpkey -algoritm RSA -out key.pem

Encrypt output private key using 128 bit AES and the passphrase ``hello'':

 openssl genpkey -algoritm RSA -out key.pem -aes-128-cbc -pass pass:hello

Generate a 2048 bit RSA key using 3 as the public exponent:

 openssl genpkey -algoritm RSA -out key.pem -pkeyopt rsa_keygen_bits:2048 \
                                                -pkeyopt rsa_keygen_pubexp:3

Generate 1024 bit DSA parameters:

 openssl genpkey -genparam -algorithm DSA -out dsap.pem \
                                                -pkeyopt dsa_paramgen_bits:1024

Generate DSA key from parameters:

 openssl genpkey -paramfile dsap.pem -out dsakey.pem

Generate 1024 bit DH parameters:

 openssl genpkey -genparam -algorithm DH -out dhp.pem \
                                        -pkeyopt dh_paramgen_prime_len:1024

Generate DH key from parameters:

 openssl genpkey -paramfile dhp.pem -out dhkey.pem