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 its unique id string) will
cause genpkey 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.
GOST2001 KEY GENERATION AND PARAMETER OPTIONS¶
Gost 2001 support is not enabled by default. To enable this algorithm, one
should load the ccgost engine in the OpenSSL configuration file. See
README.gost file in the engines/ccgost directiry of the source distribution
for more details.
Use of a parameter file for the GOST R 34.10 algorithm is optional. Parameters
can be specified during key generation directly as well as during generation
of parameter file.
- paramset:name
- Specifies GOST R 34.10-2001 parameter set according to RFC
4357. Parameter set can be specified using abbreviated name, object short
name or numeric OID. Following parameter sets are supported:
paramset OID Usage
A 1.2.643.2.2.35.1 Signature
B 1.2.643.2.2.35.2 Signature
C 1.2.643.2.2.35.3 Signature
XA 1.2.643.2.2.36.0 Key exchange
XB 1.2.643.2.2.36.1 Key exchange
test 1.2.643.2.2.35.0 Test purposes
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 -algorithm RSA -out key.pem
Encrypt output private key using 128 bit AES and the passphrase
"hello":
openssl genpkey -algorithm RSA -out key.pem -aes-128-cbc -pass pass:hello
Generate a 2048 bit RSA key using 3 as the public exponent:
openssl genpkey -algorithm 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