This is an unusual topic since most distribution create these keys for you during the installation of the OpenSSH server package. But it may be useful to be able generate new server keys from time to time, this happen to me when I duplicate Virtual Private Server which contains an installed ssh package.

How To: Generate SSH Host keys SSH is a service which most of system administrators use for remote administration of servers. When you install a fresh system, then at the start of the ssh service, it generates the host keys for your system which later on used for authentication.
You’ve successfully generated an SSH key pair on your CentOS client machine. Copy the Public Key to the Server # Now that the SSH key pair is generated, the next step is to copy the public key to the server you want to manage. The easiest and the recommended way to copy the public key to the remote server is to use the ssh-copy-id utility.
It can create RSA keys for use by SSH protocol version 1 and RSA or DSA keys for use by SSH protocol version 2. He type of key to be generated is specified with the -t option. If invoked without any arguments, ssh-keygen will generate an RSA key for use in SSH protocol 2 connections.

SSH Client: 192.168.0.12 ( Fedora 21 ) SSH Remote Host: 192.168.0.11 ( CentOS 7 ) If you are dealing with a number of Linux remote servers, then SSH Password-less login is one of the best ways to automate tasks such as automatic backups with scripts, synchronization files using SCP, and remote command execution. By default, ssh-keygen will create a 2048-bit RSA key pair, which is secure enough for most use cases (you may optionally pass in the -b 4096 flag to create a larger 4096-bit key). After entering the command, you should see the following prompt.

OpenSSH require different keys depending if you use SSH1 and/or SSH2 protocol. All keys are generated by ssh-keygen, that one should be available on your system with the ssh package. The receipt is almost the same as for generating your own keys, except that you should use an empty passphrase. Default key lengths are also appropriate (2048 bits for rsa and 1024 bits for dsa)

Centos 7 Generate Ssh Host Keys

SSH1 protocol

For SSH1 protocol, you need a rsa1 key generated has follow:

SSH2 protocol

For SSH2 protocol, you need two keys, one RSA key and one DSA key generated has follow:

Ssh Generate Host Keys Centos

Since January 2011, OpenSSH also support ECDSA key, you may generate a new one using: