Question

Suppose I need a login mechanism for a program in a Local Area Network in a company, my guess is to store a file with username/password pairs on the local server, but would the Java program be able to read/write information to the file from a local PC? It’s my first time dealing with such a task so I am a bit confused about this. Also I want to store only the passwords for the program, not the PC user.

Answer 1

Hmm, you should do it differently imho.

Write a service to authenticate against. The service is the only application allowed to read the password-file and runs on the server. The clients authenticate against that service. Once the user is authenticated, pass him an identification token that is tied to his machine and can expire after a period. Also, the machine needs to transmit some sort of digital signature to verify its integrity in an asynchronous manner. If you do this, you can verify that only authenticated users, who really are who they claim to be can access services which require the authentication token, including the authentication service itself.

BUT: I strongly suggest you get something that has already been built for such tasks. There’re things like Kerberos which have been built for such tasks. I am not a sysadmin, you might ask again at serverfault or so.

Additionally, I’d like to state that MD5 is not the toughest hash anymore. AFAIK blowfish is the way to go today, I might be wrong, though. It’s tougher than MD5 anyway, which is prone to collision-attacks already.