Category Archives: Usability

Pico part III: Making Pico psychologically acceptable to the everyday user

Many users are willing to sacrifice some security to gain quick and easy access to their services, often in spite of advice from service providers. Users are somehow expected to use a unique password for every service, each sufficiently long and consisting of letters, numbers, and symbols. Since most users do not (indeed, cannot) follow all these rules, they rely on unrecommended coping strategies that make passwords more usable, including writing passwords down, using the same password for several services, and choosing easy-­to-­guess passwords, such as names and hobbies. But usable passwords are not secure passwords and users are blamed when things go wrong.

This isn’t just unreasonable, it’s unjustified, because even secure passwords are not immune to attack. A number of security breaches have had little to do with user practices and password strength, such as the Snapchat hacking incident, theft of Adobe customer records and passwords, and the Heartbleed bug. Stronger authentication requires a stronger and more usable authentication scheme, not longer and more complex passwords.

We have been evaluating the usability of our more secure, token-­based system: Pico, a small, dedicated device that authenticates you to services. Pico is resistant to theft-resistant because it only works when it is close to its owner, which it detects by communicating with other devices you own – Picosiblings. These devices are smaller and can be embedded in clothing and accessories. They create a cryptographic “aura” around you that unlocks Pico.

For people to adopt this new scheme, we need to make sure Pico is psychologically acceptable – unobtrusive and easily and routinely used, especially relative to passwords. The weaknesses of passwords have not been detrimental to their ubiquity because they are easy to administer, well understood, and require no additional hardware or software. Pico, on the other hand, is not currently easy to administer, is not widely understood, and does require additional hardware and software. The onus is on the Pico team to make our solution convenient and easy to use. If Pico is not sufficiently more convenient to use than passwords, it is likely to be rejected, regardless of improvements to security.

This is a particular challenge because we are not merely attempting to replace passwords as they are supposed to be used but as they are actually used by real people, which is more usable, though much less secure, than our current conception of Pico.

Small electronic devices worn by the user – typically watches, wristbands, or glasses – have had limited success (e.g. Rumba Time Go Watch and the Embrace+ Wristband). Reasons include issues with the accuracy of the data they collect, time spent having to manage data, the lack of control over appearance, the sense that these technologies are more gimmicks than useful, the monetary cost, and battery life (etc.). All of these issues need to be carefully considered to pass the user’s cost-benefit analysis of adoption.

To ensure the psychological acceptability of Pico, we have been conducting user studies from the very early design stages. The point of this research is to make sure we don’t impose any restrictive design decisions on users. We want users to be happy to adopt Pico and this requires a user-­centred approach to research and development based on early and frequent usability testing.

Thus far, we have qualitatively investigated user experiences of paper prototypes of Pico, which eventually informed the design of three-­dimensional plastic prototypes (Figure 1).

Figure 1a.
Figure 1. Left: Early paper and plasticine Pico prototypes; Right: Plastic (Polymorph) low-fidelity Pico prototypes

This exploratory research provided insight into whether early Pico designs were sufficient for allowing the user to navigate through common authentication tasks. We then conducted interviews with these plastic prototypes, asking participants which they preferred and why. In the same interviews, we presented participants with a range of pseudo-­Picosiblings (Figure 2) to get an idea of the feasibility of Picosiblings from the end­user’s perspective.

Figure 2.
Figure 2. The range of pseudo-Picosiblings including everyday items (watch, keys, accessories, etc.) and standalone options (magnetic clips and free-standing coins)

The challenge seems to be in finding a balance between cost, style, and usefulness. Consider, for example, the usefulness of a watch. While we expect a watch to tell us the time (to serve a function), what we really care about is its style and cost. This is the difference between my watch and your watch, and it is where we find its selling power. Most wearable electronic devices, such as smart-­watches and fitness gadgets, advertise function and usefulness first, and then style, which is often limited to one, or maybe two, designs. And cost? Well, you’ll just have to find a way to pay for it. Pico, like these devices, could provide the potential usefulness required for widespread and enduring adoption, which, if paired with low cost and user style, should have a greater degree of success than previous wearable electronic devices.

Initial analysis of the results reveals polarised opinions of how Pico and Picosiblings should look, from being fashionable and personalizable to being disguised and discrete. Interestingly, users seemed more concerned about the security of Pico than about the security of passwords. Generally, however, the initial research indicates that users do see the usefulness of Pico as a standalone device, providing it is reliable and can be used for a wide range of services; hardware is no benefit to people unless it replaces most, if not all, passwords, otherwise it becomes another thing that people have to remember.

A legitimate concern for users is loss or theft; we are working to ensure that such incidents do not cause inconvenience or pose threat to the user by making the system easily recoverable. Related concerns relevant to possessing physical devices are durability, physical ease-­of-­use, the awkwardness of having to handle and aim the Pico at a QR code, and the everyday convenience of remembering and carrying several devices.

To make remembering and carrying several devices easier and more worthwhile, interviews revealed that Picosiblings should have more than one function (e.g. watches, glasses, ID cards). By making Picosiblings practical, users are more likely to remember to take them, and to perceive the effort of carrying them around as being outweighed by the benefit. Typically, 3-­4 items were the maximum number of Picosiblings that users said they would be happy to carry; the aim would be to reduce the required number of Picosiblings to 1 or 2 (depending on what they are), allowing users to carry more on them as “backups” if they were going to use them anyway.

Though suggested by some, the same emphasis on dual-­function was not observed for Pico, since this device serves a sufficiently valuable function in itself. However, while many found it perfectly reasonable to carry a dedicated, secure device (given its function), some did express a preference for the convenience of an App on their smartphone. To create a more streamlined experience, we are currently working on such an App, which should give these potential Pico users the flexibility they seem to desire.

By taking into account these and other user opinions before committing to a single design and implementation, we are working to ensure Pico isn’t just theoretically secure – secure only if we can rely on users to implement it properly despite any inconvenience. Instead, we can make sure Pico is actually secure, because we will be creating an authentication scheme that requires users to do only what they would do (or better, want to do) anyway. We can achieve this by taking seriously the capabilities and preferences of the end-­user.

 

Current state of anonymous email usability

As part of another project, I needed to demonstrate how the various user-interface options for sending anonymous email through Mixmaster appeared to the email sender. This is very difficult to explain in words, so I recorded some screencasts. The tools I used were the Mixmaster command line tool, the Mutt email client with Mixmaster plugin, QuickSilver Lite, and finally a web-based interface.

The project is now over, but in case these screencasts are of wider interest, I’ve put them on YouTube.

Overall, the usability of Mixmaster is not great. All of the secure options are difficult to configure and use (QuickSilver Lite is probably the best), emails take a long time to be sent, recipients of anonymous email can’t send replies, and there is a high chance that the email will be dropped en-route.

Continue reading Current state of anonymous email usability

Financial cryptography 2014

I will be trying to liveblog Financial Cryptography 2014. I just gave a keynote talk entitled “EMV – Why Payment Systems Fail” summarising our last decade’s research on what goes wrong with Chip and PIN. There will be a paper on this out in a few months; meanwhile here’s the slides and here’s our page of papers on bank security.

The sessions of refereed papers will be blogged in comments to this post.

Why dispute resolution is hard

Today we release a paper on security protocols and evidence which analyses why dispute resolution mechanisms in electronic systems often don’t work very well. On this blog we’ve noted many many problems with EMV (Chip and PIN), as well as other systems from curfew tags to digital tachographs. Time and again we find that electronic systems are truly awful for courts to deal with. Why?

The main reason, we observed, is that their dispute resolution aspects were never properly designed, built and tested. The firms that delivered the main production systems assumed, or hoped, that because some audit data were available, lawyers would be able to use them somehow.

As you’d expect, all sorts of things go wrong. We derive some principles, and show how these are also violated by new systems ranging from phone banking through overlay payments to Bitcoin. We also propose some enhancements to the EMV protocol which would make it easier to resolve disputes over Chip and PIN transactions.

Update (2013-03-07): This post was mentioned on Bruce Schneier’s blog, and this is some good discussion there.

Update (2014-03-03): The slides for the presentation at Financial Cryptography are now online.

"Perfectly" Encrypt 50 Letters By Hand

When I read about cryptography before computers, I sometimes wonder why people did this and that instead of something a bit more secure. We may ridicule portable encryption systems based on monoalphabetic or even simple polyalphabetic ciphers but we may also change our opinion after actually trying it for real.
Continue reading "Perfectly" Encrypt 50 Letters By Hand

Anatomy of Passwords

Passwords have not really changed since they were first used. Let’s go down the memory lane a bit and then analyse how password systems work and how they could be improved. You may say – forget passwords, OTP is the way forward. My next question would then be: So why do we use OTP in combination with passwords when they are so good?
Continue reading Anatomy of Passwords

A new side channel attack

Today we’re presenting a new side-channel attack in PIN Skimmer: Inferring PINs Through The Camera and Microphone at SPSM 2013. We found that software on your smartphone can work out what PIN you’re entering by watching your face through the camera and listening for the clicks as you type. Previous researchers had shown how to work out PINs using the gyro and accelerometer; we found that the camera works about as well. We watch how your face appears to move as you jiggle your phone by typing.

There are implications for the design of electronic wallets using mechanisms such as Trustzone which enable some apps to run in a more secure sandbox. Such systems try to prevent sensitive data such as bank credentials being stolen by malware. Our work shows it’s not enough for your electronic wallet software to grab hold of the screen, the accelerometers and the gyro; you’d better lock down the video camera, and the still camera too while you’re at it. (Our attack can use the still camera in burst mode.)

We suggest ways in which mobile phone operating systems might mitigate the risks. Meanwhile, if you’re developing payment apps, you’d better be aware that these risks exist.

Offender tagging

August was a slow month, but we got a legal case where our client was accused of tampering with a curfew tag, and I was asked for an expert report on the evidence presented by Serco, the curfew tagging contractor. Many offenders in the UK are released early (or escape prison altogether) on condition that they stay at home from 8pm to 8am and wear an ankle bracelet so their compliance can be monitored. These curfew tags have been used for fourteen years now but are controversial for various reasons; but with the prisons full and 17,500 people on tag at any one time, the objective of policy is to improve the system rather than abolish it.

In this spirit I offer a redacted version of my expert report which may give some insight into the frailty of the system. The logs relating to my defendant’s case showed large numbers of false alarms; some of these had good explanations (such as power cuts) but many didn’t. The overall impression is of an unreliable technology surrounded by chaotic procedures. Of policy concern too is that the tagging contractor not only supplies the tags and the back-end systems, but the call centre and the interface to the court system. What’s more, if you break your curfew, it isn’t the Crown Prosecution Service that takes you before the magistrates, but the contractor – relying on expert evidence from one of its subcontractors. Such closed systems are notoriously vulnerable to groupthink. Anyway, we asked the court for access not just to the tag in the case, but a complete set of tagging equipment for testing, plus system specifications, false alarm statistics and audit reports. The contractor promptly replied that “although we continue to feel that the defendant is in breach of the order, our attention has been drawn to a number of factors that would allow me to properly discontinue proceedings in the public interest.”

The report is published with the consent of my client and her solicitor. Long-time readers of this blog may recall similarities with the case of Jane Badger. If you’re designing systems on whose output someone may have to rely in court, you’d better think hard about how they’ll stand up to hostile review.

Security and Human Behaviour 2013

I’m liveblogging the Workshop on Security and Human Behaviour which is being held at USC in Los Angeles. The participants’ papers are here; for background, see the liveblogs for SHB 2008-12 which are linked here and here. Blog posts summarising the talks at the workshop sessions will appear as followups below. (Added: there is another liveblog by Vaibhav Garg.)