Log in as the future user of the keys on the system where the private key will be kept private.

ssh-keygen -t rsa
Enter file in which to save the key ...: <your choice>
Enter passphrase (empty for no passphrase): <your choice>


Two files should have been created, for example:

c@CW8:~$ ls -l .ssh/id_rsa*
-rw------- 1 c users 1679 Jan  4  2011 .ssh/id_rsa
-rw-r--r-- 1 c users  387 Jan  4  2011 .ssh/id_rsa.pub

The names and permissions of the keys reflect their purpose.  id_rsa.pub is the public key and can be readable by anyone.  id_rsa must be kept private.

The public key is annotated with the user name and short hostname of the system it was created on:

c@CW8:~$ tail -1 .ssh/id_rsa.pub ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQCpFeU5a3XE0y5UJWUey+LeImYraVdKvb5Fp5bQYdU0cblFGgsuU6OOZMH2yvmi4lXkCbuwpVqXMXxmu8eA70qmwRc2ouWzucAzebNVl0UKN74WgQ4lY2A7pFhv+4UapBWi39GCfQx3sofIBWwF8ccEVGzDhWJeZT+VRj6Ih9YEr2F/zYH0lYiBxL4Ly8XRLV5ixkJh7vcNXLa5KsBtGu/97oxBQJYUDbf3FpiljRcGcHz/Kgtq7J6lBvHkjzaVUeuCF99kMp36lTsX0MJgAvJMv+Edq/I7Gihlf9Vm2po4sqBH8xKEjEeiWjjBKchp0LxDs+sYL4slEexYxuODnzbT c@CW8