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Man, this sucks. This is a stupid semantic argument ("obstacle" versus "control" versus "constraint"), but it's also what's wrong with a lot of crappy security out there today. An obstacle is something you overcome. I don't think you mean it that way, but that's what a lot of people think. So, for instance, a Javascript hashing scheme backed by a Greasemonkey script that tries to verify that passwords actually make it through the hash function. That's good, because it "adds obstacles". The security of the system is the sum of the value of all the obstacles. No. The security of the system is inevitably the value of the 1-2 most important controls and constraints. Think of it like the difference between O(log n) and an O(n) algorithms: the constant factors don't mean much. So, you can do all sorts of gymnastics with hashes and nonces and salts (and timestamps and sequence numbers and MACs), but you turn SSL on, and now the only thing that matters is SSL. The "obstacle" mindset, also known as "defense in depth", is what gets us IPS, web application firewalls, and antivirus. None of these $50,000 products work. But they're defended by managers and purchasers and vendors as "another layer in a defense in depth strategy". What we need is software that works, with defenses that are clear and fundamentally sound. What we get, too often, is band-aids. Again, I apologize, because I'm turning you into a straw man and I don't mean to. The word "obstacle" sets me off. It shouldn't, because obstacles pay for my consulting team and my development team. I should say, "more obstacles, please!" "Please, build another ActiveX control to implement an AES challenge-response protocol with a compiled-in key!" "Please, build another web filter for which every nonminimal UTF-8 encoding variant is another security advisory for!" Oh well. I'm old. By the way, being somewhat close to the drama here, I want to note that the "new Threat Modeling" is a bit controversial, the terms are still up in the air, and if you want to learn more about security, you'd be far better off reading Ferguson's "Practical Cryptography" and McDonald, Dowd, and Schuh's "Art of Software Security Assessment". Don't build obstacle courses. Design stuff that works. |
Just as a side note: SSL libraries are big, ugly, and bug-prone. If you use SSL for user logins, your users' login information will be more secure... but your server will be less secure.