Lockpicking and the Internet
By Bruce Schneier
Physical locks aren't very good. They keep the honest out, but any burglar worth his salt can pick the common door lock pretty quickly.
It used to be that most people didn't know this. Sure, we all watched television criminals and private detectives pick locks with an ease only found on television and thought it realistic, but somehow we still held onto the belief that our own locks kept us safe from intruders.
The Internet changed that.
First was the MIT Guide to Lockpicking (PDF), written by the late Bob ("Ted the Tool") Baldwin. Then came Matt Blaze's 2003 paper (PDF) on breaking master key systems. After that, came a flood of lock picking information on the Net: opening a bicycle lock with a Bic pen, key bumping (PDF), and more. Many of these techniques were already known in both the criminal and locksmith communities. The locksmiths tried to suppress the knowledge, believing their guildlike secrecy was better than openness. But they've lost (PDF): never has there been more public (PDF) information about lock picking -- or safecracking (PDF), for that matter.
Lock companies have responded with more complicated locks, and more complicated disinformation campaigns.
There seems to be a limit to how secure you can make a wholly mechanical lock, as well as a limit to how large and unwieldy a key the public will accept. As a result, there is increasing interest in other lock technologies.
As a security technologist, I worry that if we don't fully understand these technologies and the new sorts of vulnerabilities they bring, we may be trading a flawed technology for an even worse one. Electronic locks are vulnerable to attack, often in new and surprising ways.
Start with keypads, more and more common on house doors. These have the benefit that you don't have to carry a physical key around, but there's the problem that you can't give someone the key for a day and then take it away when that day is over. As such, the security decays over time -- the longer the keypad is in use, the more people know how to get in. More complicated electronic keypads have a variety of options for dealing with this, but electronic keypads work only when the power is on, and battery-powered locks have their own failure modes. Plus, far too many people never bother to change the default entry code.
Keypads have other security failures, as well. I regularly see keypads where four of the 10 buttons are more worn than the other six. They're worn from use, of course, and instead of 10,000 possible entry codes, I now have to try only 24.
Fingerprint readers are another technology, but there are many known security problems with those. And there are operational problems, too: They're hard to use in the cold or with sweaty hands; and leaving a key with a neighbor to let the plumber in starts having a spy-versus-spy feel.
Some companies are going even further. Earlier this year, Schlage launched a series of locks that can be opened either by a key, a four-digit code, or the Internet. That's right: The lock is online. You can send the lock SMS messages or talk to it via a Website, and the lock can send you messages when someone opens it -- or even when someone tries to open it and fails.
Sounds nifty, but putting a lock on the Internet opens up a whole new set of problems, none of which we fully understand. Even worse: Security is only as strong as the weakest link. Schlage's system combines the inherent "pickability" of a physical lock, the new vulnerabilities of electronic keypads, and the hacking risk of online. For most applications, that's simply too much risk.
Schneier.com is a personal website. Opinions expressed are not necessarily those of BT.