Tag Archives: Pico

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.


Pico part II: What’s wrong with QR code password replacement schemes, and how to fix them!

Users don’t want to authenticate, they want to do useful or enjoyable things like sending emails, ordering groceries or playing games. To alleviate the burden of having to type passwords, Pico and several other schemes, such as SQRL and tiQR, let the user simply scan a QR code; then a cryptographic protocol authenticates the user behind the scenes and initiates a session. But users, unless they are on the move, may prefer to run their email or web browsing sessions on their full-size computer instead of on their  smartphone, whose user interface is relatively limited. Therefore they don’t want an authenticated session between their smartphone and the website but between their computer and the website, even if it’s the smartphone that scans the QR code.

In the original 2011 Pico paper (footnote 37), the website kept track of which “page impression” from a web browser was related to which Pico authentication by including a nonce in each login page QR code and having the Pico sign and return it as part of the authentication. Since then, within the Pico team, there has been much discussion of the so-called Page Impression Nonce or PIN, infamous both for the attacks it enables and its unfortunate, overloaded acronym. While other schemes may have called it something different, or not called it anything at all, it was always present in one form or another because they all used it to solve this same problem of linking browser sessions to authentications.

For example, in the SQRL system each QR code contains a URL, part of which is a random nonce (the PIN in this system). The SQRL app must sign and return this URL, thus associating the nonce with the app’s per-verifier public key. The web browser then starts its session by making another request which includes the URL (and thus the PIN) and gets back a session cookie.

So what’s the problem?

The problem with this kind of mechanism is that anyone else who learns the PIN can also make that second request, thus logging themselves in as the user who scanned the QR code. For example, a bad guy can obtain a QR code and its PIN from the login page of bank.com and display it somewhere, like the login page of randomgameforum.com, for a victim to scan. Now, assuming the victim had an account at bank.com, the attacker obtains a bank.com session that the victim unsuspectingly initiated with their smartphone.

Part of the problem is that QR codes are not human-readable. Some have suggested that a simple confirmation step (“Do you really want to login to bank.com?”) might prevent such attacks, but we decided this wasn’t really good enough from a security or a usability perspective. We don’t want users to have to read the confirmation dialog and press the OK button every time they authenticate, and realistically they won’t, especially if they never normally do anything other than press OK.

Moreover, the confirmation step doesn’t help at all when the relaying of the QR code is combined with traditional phishing techniques. Consider receiving this email:

From: security@bank.com
To: victim@example.com
Subject: Urgent: Account security threat
Dear Customer

<compelling phishing mumbo jumbo>

To keep your account secure, please scan this QR code:

<login QR code with PIN known by the sender>

Kind regards,

Account security department

and if you oblige:

Do you really want to login to bank.com?

Now the poor user thinks “Well yes, I do, that’s exactly what the account security team asked me to do” and even worse: “I’m definitely not being phished, I remember what those security people kept telling me about checking the address of the website before logging in”.

How to fix it

The solution we came up with is called session delegation. Instead of having a nonce in each QR code, which anyone can later trade-in for an authenticated session, we have the website return a session delegation token to the Pico (not the web browser) as part of the authentication protocol. The Pico may then delegate the session to the browser on the bigger computer by sending it this token, via a secure channel. (For further details see section 4.1 of our “lousy phish” paper.) The price to pay for this strategy is that it requires a channel from the Pico to the browser, which is much harder to provide than the one in the opposite direction (the visual “QR code” channel).

We made a prototype which used Bluetooth for the delegation channel but, because Bluetooth was sometimes difficult to set up and not universally available, we even thought about using an audio cable plugged into the microphone jack of the computer. However, we were still worried about the availability and usability of these hardware-based solutions. We did a lot of research into NAT and firewall traversal techniques (such as STUN and TURN) to see if we could use peer-to-peer IP connectivity, but this is not possible in all cases without a separate signalling channel. In our latest prototype we’re using a “rendezvous point”, which is a very simple relay server we’ve designed, running in the public Internet. The rendezvous point is the most universal and usable solution, but does come with some privacy concerns, namely that the untrusted rendezvous server gets to see the Pico/computer IP address pairs which are communicating. So we still allow privacy-conscious users to adopt less convenient alternatives if they’re willing to pay the price of setting up Bluetooth, connecting cables or changing their firewall/NAT settings, but we don’t impose that cost on everyone.

The drawback of this approach is that the user’s computer requires some Pico software to receive the delegation tokens, via the rendezvous point or whatever other channel. Having to install these hurts the “deployability” of the system as a whole and could render it completely useless in situations where installing new software is not possible. But another innovation, making the delegation token take the form of a URL, means there is always a last-resort fallback channel: manual transcription. If a Pico user can’t install the software on, or doesn’t want to trust, a particular computer, they can always still retype the token URL. There are other security concerns related to having URLs which will log your browser into someone else’s account, but you’ll have to read the lousy phish paper for a more detailed discussion of this topic.

There is clearly much interest in finding a replacement for passwords and several schemes (such as US 8261089 B2Snap2Pass, tiQR, US 20130219479 A1, QRAuth, SQRL) propose using QR codes. But upon close inspection, all of the above use a page impression nonce, making them vulnerable to session hijacking attacks. We rejected the idea that this could be solved simply by getting the user to carry out more checks and instead we propose an architectural fix which provides a more secure basis for the design of Pico.

For more information about Pico, have a look at our website, sign up to our mailing list and stay tuned for more Pico-related posts on Light Blue Touchpaper in the near future.