The backdoor problem
22 December 2011
There’s a well known truism in the security community that says that a system’s security is only as good as the backup entry method employed. That’s as true on the web as elsewhere. People forget or lose their passwords, they want to be able to get back into their accounts, and many websites give them the chance to do so by offering entry through a “backdoor”. The backdoor is meant to recognize and grant entry to the true account owner by asking “security questions” for which only he would know the answer.
The problem is that most security question answers, if generated as intentioned, typically make poor passwords. You can have the strongest primary password in the world, but if you use your mother’s maiden name as the answer to the security question a website offers, then you can forget about the strength of your primary password. Your effective password might as well be your mother’s maiden name, since knowledge of that will get you into the website as sure as knowledge of the primary password will.
You should keep that in mind when creating answers to security questions. Instead of providing the actual answers, I recommend creating real passwords as answers to these (i.e., your mother’s maiden name could be entered as “d9IgzUe33s”), then keeping track of these additional passwords in a program built for the job (I’ve discussed such programs before).
The fortress problem
Now that you’ve gussied up the backdoor, strengthening it with a stronger password requirement, you may run into the problem that backdoors were invented to solve: what if you suddenly find yourself locked out of your fortress? What if you lose both passwords? If you are using a password management tool, what if your password database gets corrupted? What if you accidentally erase an entry in your database (this is scarily easy to do)? What if your hard disk crashes and you lose your database?
The answer is that you need to create backup systems for yourself. These backups need to be in two forms:
- If you use a password manager, create backups of your password database. After creating a new entry, store a copy of the database on a USB flash drive or send a copy to a family member’s email address. As long as the database itself is password protected, you needn’t worry about making copies and leaving them lying around or giving possession to others. In fact, the more copies you make and the easier they are to find, the better.
- If you use a password manager, you need to protect against the possibility that you forget the master password that unlocks the database. If you’ve used this method, that should never happen. But sometimes bad things do happen, and you should plan for that. A low-tech method would be to write down your database password and store it in your wallet. That is safer and more sensible than many people suspect. A second option would be to write down your master password and store it in a safety deposit box at your bank. The latter option has the advantage of finally sealing up that backdoor to be both safe and useful – if you lose your safety deposit box key, for example, you can regain access to it by proving your identity to your bank, something that should be extremely difficult to do for an imposter but relatively easy for the true account holder to do.
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