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.
- Openssl Generate Public Private Key
- Private Key Definition
- Generate Public Key From Private Key Using Openssl Free
Public keys come in several flavors, using different cryptographic algorithms. The most popular ones associated with certificates are RSA and DSA, and this article will show how to generate each of them.
Generating an RSA key
While Encrypting a File with a Password from the Command Line using OpenSSL is very useful in its own right, the real power of the OpenSSL library is its ability to support the use of public key cryptograph for encrypting or validating data in an unattended manner (where the password is not required to encrypt) is done with public keys.
A RSA key can be used both for encryption and for signing and generating a key is quite easy, all you have to do is the following:
Openssl Generate Public Private Key
That will generate a private key with is password protected (it will prompt you for the password during generation). If you don’t want it password protected (usually for server side use) then leave the -des3 parameter out, i.e.:
Private Key Definition
Generating a DSA key
A DSA key can be used for signing only. This is important to keep in mind to know what kind of purposes 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 then to generate the key itself.
Again like RSA, 2048 is the size of the key, in bits with anything smaller than 2048 being insecure in todays standards.
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Generate Public Key From Private Key Using Openssl Free
Also the -des3 parameter will prompt you for a pass phrase – for server use leave it out: