Under GDPR, IP addresses are personal data. I have no need to trace back IP to specific users, but I would like to limit downloads to one per IP.* I do not want to store plain IPs.
My first solution would be to hash the IP. I could store the hash:
The problem is that hashing all 4 294 967 296 possible IP addresses is simple, and someone will easily find that
127.0.0.1 is the stored IP.
Adding a salt holds the same problem, you can calculate all the IPs again with this salt and arrive at the same problem.
Is there a solution for this?
* Use case here is simplified, please do not comment on reasons why I want this. ;)