Owl’s Portfolio

Seems like every time I go to a security conference these days there’s at least one short talk where people are proposing to start over and rebuild the computer universe from scratch and make it simple and impossible to use wrong this time and it will be so awesome. Readers, it’s not going to work. And it’s not just a case of nobody’s going to put in enough time and effort to make it work. The idea is doomed from eight o’clock, Day One.

We all know from practical experience that a software module that’s too complicated is likely to harbor internal bugs and is also likely to induce bugs in the code that uses it. But we should also know from practice that a software module that’s too simple may work perfectly itself but will also induce bugs in the code that uses it! “One size fits all” APIs are almost always too inflexible, and so accumulate a “scar tissue” of workarounds, which are liable to be buggy. Is this an accident of our human fallibility? No, it is an inevitable consequence of oversimplification.

To explain why this is so, I need to talk a little about cybernetics. In casual usage, this word is a sloppy synonym for robotics and robotic enhancements to biological life (cyborgs), but as a scientific discipline it is the study of dynamic control systems that interact with their environment, ranging in scale from a simple closed-loop feedback controller to entire societies.¹ The Wikipedia article is decent, and if you want more detail, the essay “Cybernetics of Society” is a good starting point. Much of the literature on cybernetics talks about interacting systems of people—firms, governments, social clubs, families, etc—but is equally applicable to systems of, around, or within computers. One of the fundamental conclusions of cybernetics, evident for instance in Stafford Beer’s viable system model, is that a working system must be as least as complex as the systems it interacts with. If it isn’t, it will be unable to cope with all possible inputs. This is a theoretical explanation for the practical observation above, and it lets us put a lower bound on the complexity of a real-world computer system.

Let’s just look at one external phenomenon nearly every computer has to handle: time. Time seems like it ought to be an easy problem. Everyone on Earth could, in principle, agree on what time it is right now. Making a good clock requires precision engineering, but the hardware people have that covered; a modern $5 wristwatch could have earned you twenty thousand pounds in 1714. And yet the task of converting a count of seconds to a human-readable date and vice versa is so hairy that people write 500-page books about that alone, and the IANA has to maintain a database of time zones that has seen at least nine updates a year every year since 2006. And that’s just one of the things computers have to do with time. And handling time correctly can, in fact, be security-critical.

I could assemble a demonstration like this for many other phenomena whose characteristics are set by the non-computerized world: space, electromagnetic waves, human perceptual and motor abilities, written language, mathematics, etc. etc. (I leave the biggest hairball of all—the global information network—out, because it’s at least nominally in-scope for these radical simplification projects.) Computers have to cope with all of these things in at least some circumstances, and they all interact with each other in at least some circumstances, so the aggregate complexity is even higher than if you consider each one in isolation. And we’re only considering here things that a general-purpose computer has to be able to handle before we can start thinking about what we want to use it for; that’ll bring in all the complexity of the problem domain.

To be clear, I do think that starting over from scratch and taking into account everything we’ve learned about programming language, OS, and network protocol design since 1970 would produce something better than what we have now. But what we got at the end of that effort would not be notably simpler than what we have now, and although it might be harder to write insecure (or just buggy) application code on top of it, it would not be impossible. Furthermore, a design and development process that does not understand and accept this will not produce an improvement over the status quo.

¹ The casual-use meaning of “cybernetics” comes from the observation (by early AI researchers) that robots and robotic prostheses were necessarily cybernetic systems, i.e. dynamic control systems that interacted with their environment.

Your post advocates a

□ software □ hardware □ cognitive □ two-factor □ other _________

universal replacement for passwords. Your idea will not work. Here is why it won’t work:

□ It’s too easy to trick users into revealing their credentials
□ It’s too hard to change a credential if it’s stolen
□ It initiates an arms race which will inevitably be won by the attackers
□ Users will not put up with it
□ Server administrators will not put up with it
□ Web browser developers will not put up with it
□ National governments will not put up with it
□ Apple would have to sacrifice their extremely profitable hardware monopoly
□ It cannot coexist with passwords even during a transition period
□ It requires immediate total cooperation from everybody at once

Specifically, your plan fails to account for these human factors:

□ More than one person might use the same computer
□ One person might use more than one computer
□ One person might use more than one type of Web browser
□ People use software that isn’t a Web browser at all
□ People want to present different facets of their identity in different contexts
□ Not everyone can see the difference between red and green
□ Not everyone can make fine motor movements with that level of precision
□ Not everyone has thumbs
□ No one wants to remember a string of meaningless symbols that long
□ Users rapidly learn to ignore security alerts of this type

and technical obstacles:

□ Clock skew
□ Unreliable servers
□ Network latency
□ Wireless eavesdropping and jamming
□ Zooko’s Triangle
□ Computers do not necessarily have any USB ports
□ SMTP messages are often recoded or discarded in transit
□ SMS messages are trivially forgeable by anyone with a PBX

and the following philosophical objections may also apply:

□ This protocol was shown to be insecure by ________________, ____ years ago
□ This protocol must be implemented perfectly or it is insecure
□ This protocol relies on a psychologically unnatural notion of “trustworthiness”
□ This secret is even easier to guess by brute force than the typical password
□ This secret is even less memorable than the typical password
□ It’s too hard to type something that complicated on a phone keyboard
□ Not everyone trusts your government
□ Not everyone trusts their own government
□ Who’s going to run this brand new global, always-online directory authority?
□ I should be able to authenticate a local communication without Internet access
□ I should be able to communicate without having met someone in person first
□ Anonymity is vital to robust public debate

To sum up,

□ It’s a decent idea, but I don’t think it will work. Keep trying!
□ This is a terrible idea and you should feel terrible.
□ You are the Russian Mafia and I claim my five pounds.

hat tip to the original

It’s professional-organization management election time again. This is my response to everyone who’s about to send me an invitation to vote for them:

When it comes to ACM and IEEE elections, I am a single-issue voter, and the issue is open access to research. I will vote for you if and only if you make a public statement committing to aggressive pursuit of the following goals within your organization, in decreasing order of priority:

1. As immediately as practical, begin providing to the general public zero-cost, no-registration, no-strings-attached online access to new publications in your organization’s venues.

2. Commit to a timetable (which should also be as quickly as practical, but could be somewhat slower than for the above) for opening up your organization’s older publications to zero-cost, no-registration, no-strings-attached online access.

3. Abandon the practice of requiring authors to assign copyright to your organization; instead, require only a license substantively similar to that requested by USENIX (exclusive publication rights for no longer than 12 months with exception for posting an electronic copy on your own website, nonexclusive right to continue disseminating afterward).

4. On a definite timetable, revert copyright to all authors who published under the old copyright policy, retaining only the rights requested under the new policy.

Thank you for your consideration.