Encrypted logins?

Is there a way to set up an encrypted login session, whereby the calling program would need a 'key' in order to decrypt the connection to even see the 'login: ' prompt? I thought I saw something like this for the ham-radio enthusiasts. It uses plain-DES to do the work. But this would require that your calling program be some type of comm prog with the decryption/encryption abilities within. I understand that some gov logins use this type of scheme.