A performance hit on your web servers might very well be worth it if it means your database can cope with your data better, though obviously, test that. It tend

A performance hit on your web servers might very well be worth it if it means your database can cope with your data better, though obviously, test that. It tends to be a little more difficult to scale up your database server than your web server. The other side of it is that safety from enumeration attempts is the sort of thing that gets added on well after the software's actually in use, unfortunately, and changing existing keys might not be practical. A social network I use is in the position where they don't really want people enumerating their users by ID... but all their users are identified in the URL by sequential ID. An HMAC would help them, and isn't difficult to implement. And yeah, bad implementations are bad, but I wouldn't trust someone who can't use an HMAC securely to generate and use unguessable IDs properly either.