SSH protocol provides different ways for authentication. Key based authentication is the most secure one. In order to use key based authentication we should store the key in a command place. SSH agents reads keys and uses for authentication with remote system. We can use ssh-add to store keys in a common path.

Key Files

Public and private keys are store in files according to their algorithm.

• ~/.ssh/identity  holds RSA version 1 identity
• ~/.ssh/id_dsa  holds DSA version 2 identity
• ~/.ssh/id_rsa holds RSA version 2 identity

If identity keys are readable by others they can not used by ssh-add.

Start Ssh Agent

ssh-agent  is used to read keys for authentication. ssh-agent  works as daemon. We can simply start it like below.

$ eval `ssh-agent`

Add Ssh Key

We will add ssh keys with the ssh-add . We will provide the key we want to add. If the key is protected with encryption we need to provide the password. In this example we will add key named mykey . This key is located in the current working directory but we can also provide absolute path of the key.

$ ssh-add mykey

List Ssh Keys

We can list added ssh keys with the -L  option like below. This will also print the type of the key with the name at the end of the line.

$ ssh-add -L