For a secure environment, its not enough to implement  only authentication  and authorization. you need a secure protocol to perform encryptions, tunnelling and transaction monitoring.

Depending on your remote connectivity nature use protocols like HTTPS, SSL and ofcourse perform whatever cryptography, key signature and certification methods you have handy.

Aside from JAAS (which provides necessary functionality), you need to implement secure network topology. (for this read through how to setup firewalls and become familiar with firewalls and DMZ combinations.

J2EE security  blueprint is a good place to start.