I'm looking at whats nessecary to create a small accounts server for a video game I'm programming in my spare time. User privacy is a very important topic for me, and I don't want to keep anything about my users that isn't really needed to provide the service I'm offering. I don't feel I have the right require that info, and I don't really want the responsibility of protecting that info (Don't get me wrong though I'll still do whatever is nessecary to protect what I do take).
My primary idea for this is to store unsalted email hashes as the account identifiers, the usual salt+hash password, and no other identifying information. I haven't really seen mention of this done previously so I'd like to confirm that the idea is sound. With this system I can still send emails to users for things like password recovery since they will still need to send me their plaintext email to log in.
Is this a good idea? If I retain IP addresses for logging purposes and link IPs to accounts, will a hacker be able to match the IPs elsewhere and work out/guess many emails anyway? Is a large list of user IPs valuable to anyone?
Are there any other methods for minimising identifying and private information while still ensuring that each user can only log into their own account (such as password alternatives)?