>>xvecto+W4
For ipv4 is there a difference between storing IPs and storing their hash with a nonce? You can calculate the hash of every IP address in reasonable time, so it's reversible.
Only benefit I can think of is you can forget the nonce and now the data is securely useless, if the nonce was secure, but that doesn't seem that useful really.
>>kadoba+K5
I think if we use a difficult enough hash function it should be okay? With 4 billion IPv4 addresses it would take 120+ years to iterate through all of them. You could probably rotate the nonce periodically, making it effectively worthless to pre-compute any table. But this gets complicated fast.
>>xvecto+Ra
Except you are still storing the nonce/salt (not sure which you are proposing)...which means you can reverse it, so the data is subpoenable. It doesn't really buy anyone anything, in this scenario. It could help if the logs were stolen, but that isn't what is being discussed here.