authorized keys.en
The authorized_keys allows you to access the router with pre-shared keys i.s.o. just a password. To use pre-shared keys you need to generate a public/private keypair and add the public key to the authorized_keys file.
You also need to setup your SSH client for using the pre-shared key. A good howto for PuTTY can be found here.
[[[Authorized
keys setup]]]