mirror of
https://github.com/openssl/openssl.git
synced 2024-12-21 06:09:35 +08:00
003ef7ef9a
Seems this documentation is not dead, so add this missing part Reviewed-by: Rich Salz <rsalz@openssl.org> Reviewed-by: Andy Polyakov <appro@openssl.org> (Merged from https://github.com/openssl/openssl/pull/4037)
106 lines
3.6 KiB
Plaintext
106 lines
3.6 KiB
Plaintext
<DRAFT!>
|
|
HOWTO keys
|
|
|
|
1. Introduction
|
|
|
|
Keys are the basis of public key algorithms and PKI. Keys usually
|
|
come in pairs, with one half being the public key and the other half
|
|
being the private key. With OpenSSL, the private key contains the
|
|
public key information as well, so a public key doesn't need to be
|
|
generated separately.
|
|
|
|
Public keys come in several flavors, using different cryptographic
|
|
algorithms. The most popular ones associated with certificates are
|
|
RSA and DSA, and this HOWTO will show how to generate each of them.
|
|
|
|
|
|
2. To generate a RSA key
|
|
|
|
A RSA key can be used both for encryption and for signing.
|
|
|
|
Generating a key for the RSA algorithm is quite easy, all you have to
|
|
do is the following:
|
|
|
|
openssl genrsa -des3 -out privkey.pem 2048
|
|
|
|
With this variant, you will be prompted for a protecting password. If
|
|
you don't want your key to be protected by a password, remove the flag
|
|
'-des3' from the command line above.
|
|
|
|
The number 2048 is the size of the key, in bits. Today, 2048 or
|
|
higher is recommended for RSA keys, as fewer amount of bits is
|
|
consider insecure or to be insecure pretty soon.
|
|
|
|
|
|
3. To generate a DSA key
|
|
|
|
A DSA key can be used for signing only. It is important to
|
|
know what a certificate request with a DSA key can really be used for.
|
|
|
|
Generating a key for the DSA algorithm is a two-step process. First,
|
|
you have to generate parameters from which to generate the key:
|
|
|
|
openssl dsaparam -out dsaparam.pem 2048
|
|
|
|
The number 2048 is the size of the key, in bits. Today, 2048 or
|
|
higher is recommended for DSA keys, as fewer amount of bits is
|
|
consider insecure or to be insecure pretty soon.
|
|
|
|
When that is done, you can generate a key using the parameters in
|
|
question (actually, several keys can be generated from the same
|
|
parameters):
|
|
|
|
openssl gendsa -des3 -out privkey.pem dsaparam.pem
|
|
|
|
With this variant, you will be prompted for a protecting password. If
|
|
you don't want your key to be protected by a password, remove the flag
|
|
'-des3' from the command line above.
|
|
|
|
|
|
4. To generate an EC key
|
|
|
|
An EC key can be used both for key agreement (ECDH) and signing (ECDSA).
|
|
|
|
Generating a key for ECC is similar to generating a DSA key. These are
|
|
two-step processes. First, you have to get the EC parameters from which
|
|
the key will be generated:
|
|
|
|
openssl ecparam -name prime256v1 -out prime256v1.pem
|
|
|
|
The prime256v1, or NIST P-256, which stands for 'X9.62/SECG curve over
|
|
a 256-bit prime field', is the name of an elliptic curve which generates the
|
|
parameters. You can use the following command to list all supported curves:
|
|
|
|
openssl ecparam -list_curves
|
|
|
|
When that is done, you can generate a key using the created parameters (several
|
|
keys can be produced from the same parameters):
|
|
|
|
openssl genpkey -des3 -paramfile prime256v1.pem -out private.key
|
|
|
|
With this variant, you will be prompted for a password to protect your key.
|
|
If you don't want your key to be protected by a password, remove the flag
|
|
'-des3' from the command line above.
|
|
|
|
You can also directly generate the key in one step:
|
|
|
|
openssl ecparam -genkey -name prime256v1 -out private.key
|
|
|
|
or
|
|
|
|
openssl genpkey -algorithm EC -pkeyopt ec_paramgen_curve:P-256
|
|
|
|
|
|
5. NOTE
|
|
|
|
If you intend to use the key together with a server certificate,
|
|
it may be reasonable to avoid protecting it with a password, since
|
|
otherwise someone would have to type in the password every time the
|
|
server needs to access the key.
|
|
|
|
For X25519, it's treated as a distinct algorithm but not as one of
|
|
the curves listed with 'ecparam -list_curves' option. You can use
|
|
the following command to generate an X25519 key:
|
|
|
|
openssl genpkey -algorithm X25519 -out xkey.pem
|