This won't make an appreciable difference if your entire db is captured by the attacker (ala LinkedIn). You are just asking them to buy a box (rent a virtual s

This won't make an appreciable difference if your entire db is captured by the attacker (ala LinkedIn). You are just asking them to buy a box (rent a virtual server) with more RAM because the equals operation just became memory intensive. A machine with 128GB of RAM will still give a near-constant result to "does my test hash equal the user's password?" "Just add more fake hashes", you say. To get around the above, you have to use billions upon billions of fake hashes. The database abuse will eventually catch up to you. This is trying to accomplish what bcrypt and scrypt do using tunable parameters, which is force the attacker to spend significantly more to break passwords than it costs you to test passwords (because they are doing it billions of times, you are doing it once). Personally, I trust the math more.