A hash (whether MD5 or some SHA) on IP4-address is easily reversed. Summing octets is non-reversable, so it seems like a good 'hash' to me (but note: you'll ge

A hash (whether MD5 or some SHA) on IP4-address is easily reversed. Summing octets is non-reversable, so it seems like a good 'hash' to me (but note: you'll get a lot of collisions). And of course, IANAL.