The end of the billion-user Password:Impossible

XKCD: “Password Strength”

This week, the Wall Street Journal published an article by Robert McMillan containing an apology from Bill Burr, a man whose name is unknown to most but whose work has caused daily frustration and wasted time for probably hundreds of millions of people for nearly 15 years. Burr is the author of the 2003 Special Publication 800-63. Appendix A from the US National Institute of Standards and Technology: eight pages that advised security administrators to require complex passwords including special characters, capital letters, and numbers, and dictate that they should be frequently changed.

“Much of what I did I now regret,” Burr told the Journal. In June, when NIST issued a completely rewritten document, it largely followed the same lines as the NCSCs password guidance, published in 2015 and based on prior research and collaboration with the UK Research Institute in Science of Cyber Security (RISCS), led from UCL by Professor Angela Sasse. Yet even in 2003 there was evidence that Burr’s approach was the wrong one: in 1999, Sasse did the first work pointing out the user-unfriendliness of standard password policies in the paper Users Are Not the Enemy, written with Anne Adams.

How much did that error cost in lost productivity and user frustration? Why did it take the security industry and research community 15 years to listen to users and admit that the password policies they were pushing were not only wrong but actively harmful, inflicting pain on millions of users and costing organisations huge sums in lost productivity and administration? How many other badly designed security measures are still out there, the cyber equivalent of traffic congestion and causing the same scale of damage?

For decades, every password breach has led to the same response, which Einstein would readily have recognised as insanity: ridiculing users for using weak passwords, creating policies that were even more difficult to follow, and calling users “stupid” for devising coping strategies to manage the burden. As Sasse, Brostoff, and Weirich wrote in 2001 in their paper Transforming the ‘Weakest Link’, “…simply blaming users will not lead to more effective security systems”. In his 2009 paper So Long, and No Thanks for the Externalities, Cormac Herley (Microsoft Research) pointed out that it’s often quite rational for users to reject security advice that ignores the indirect costs of the effort required to implement it: “It makes little sense to burden all users with a daily task to spare 0.01% of them a modest annual pain,” he wrote.

When GCHQ introduced the new password guidance, NCSC head Ciaran Martin noted the cognitive impossibility of following older policies, which he compared to trying to memorise a new 600-digit number every month. Part of the basis for Martin’s comments is found in more of Herley’s research. In Password Portfolios and the Finite-Effort User, Herley, Dinei Florencio, and Paul C. van Oorschot found that the cognitive load of managing 100 passwords while following the standard advice to use a unique random string for every password is equivalent to memorising 1,361 places of pi or the ordering of 17 packs of cards – a cognitive impossibility. “No one does this”, Herley said in presenting his research at a RISCS meeting in 2014.

The first of the three questions we started with may be the easiest to answer. Sasse’s research has found that in numerous organisations each staff member may spend as much as 30 minutes a day on entering, creating, and recovering passwords, all of it lost productivity. The US company Imprivata claims its system can save clinicians up to 45 minutes per day just in authentication; in that use case, the wasted time represents not just lost profit but potentially lost lives.

Add the cost of disruption. In a 2014 NIST diary study, Sasse, with Michelle Steves, Dana Chisnell, Kat Krol, Mary Theofanos, and Hannah Wald, found that up to 40% of the time leading up to the “friction point” – that is, the interruption for authentication – is spent redoing the primary task before users can find their place and resume work. The study’s participants recorded on average 23 authentication events over the 24-hour period covered by the study, and in interviews they indicated their frustration with the number, frequency, and cognitive load of these tasks, which the study’s authors dubbed “authentication fatigue”. Dana Chisnell has summarised this study in a video clip.

The NIST study identified a more subtle, hidden opportunity cost of this disruption: staff reorganise their primary tasks to minimise exposure to authentication, typically by batching the tasks that require it. This is a similar strategy to deciding to confine dealing with phone calls to certain times of day, and it has similar consequences. While it optimises that particular staff member’s time, it delays any dependent business process that is designed in the expectation of a continuous flow from primary tasks. Batching delays result not only in extra costs, but may lose customers, since slow responses may cause them to go elsewhere. In addition, staff reported not pursuing ideas for improvement or innovation because they couldn’t face the necessary discussions with security staff.

Unworkable security induces staff to circumvent it and make errors – which in turn lead to breaches, which have their own financial and reputational costs. Less obvious is the cost of lost staff goodwill for organisations that rely on free overtime – such as US government departments and agencies. The NIST study showed that this goodwill is dropping: staff log in less frequently from home, and some had even returned their agency-approved laptops and were refusing to log in from home or while travelling.

It could all have been so different as the web grew up over the last 20 years or so, because the problems and costs of password policies are not new or newly discovered. Sasse’s original 1999 research study was not requested by security administrators but by BT’s accountants, who balked when the help desk costs of password problems were tripling every year with no end in sight. Yet security people have continued to insist that users must adapt to their requirements instead of the other way around, even when the basis for their ideas is shown to be long out of date. For example, in a 2006 blog posting Purdue University professor Gene Spafford explained that the “best practice” (which he calls “infosec folk wisdom”) of regular password changes came from non-networked military mainframes in the 1970s – a far cry from today’s conditions.

Herley lists numerous other security technologies that are as much of a plague as old-style password practices: certificate error warnings, all of which are false positives; security warnings generally; and ambiguous and non-actionable advice, such as advising users not to click on “suspicious” links or attachments or “never” reusing passwords across accounts.

All of these are either not actionable, or just too difficult to put into practice, and the struggle to eliminate them has yet to bear fruit. Must this same story continue for another 20 years?


This article also appears on the Research Institute in Science of Cyber Security (RISCS) blog.

Observing the WannaCry fallout: confusing advice and playing the blame game

As researchers who strive to develop effective measures that help individuals and organisations to stay secure, we have observed the public communications that followed the Wannacry ransomware attack of May 2017 with increasing concern. As in previous incidents, many descriptions of the attack are inaccurate – something colleagues have pointed out elsewhere. Our concern here is the advice being disseminated, and the fact that various stakeholders seem to be more concerned with blaming each other than with working together to prevent further attacks affecting organisations and individuals.

Countries initially affected in WannaCry ransomware attack (source Wikipedia, User:Roke)

Let’s start with the advice that is being handed out. Much of it is unhelpful at best, and downright wrong at worst – a repeat of what happened after Heartbleed, when people were advised to change their passwords before the affected organisations had patched their SSL code. Here is a sample of real advice sent out to staff in major organisation post-WannaCry:

“We urge you to be vigilant and not to open emails that are unexpected, unusual or suspicious in any way. If you experience any unusual computer behaviour, especially any warning messages, please contact your IT support immediately and do not use your computer further until advised to do so.”

Useful advice has to be correct and actionable. Users have to cope with dozens, maybe hundreds, of unexpected emails every day, most containing links and many accompanied by attachments, cannot take ten minutes to ponder each email before deciding whether to respond. Such instructions also implicitly and unfairly suggest that users’ ordinary behaviour plays a major role in causing major incidents like this one. RISCS advocates enlisting users as part of frontline defence. Well-targeted, automated blocking of malicious emails lessen the burden on individual users, and build resilience for the organisation in general.

In an example of how to confuse users, The Register reports that City of London Police sent out its “advice” via email in an attachment entitled “ransomware.pdf”. So users are simultaneously exhorted to be “vigilant” and not open emails and required to open an email in order to get that advice. The confusion resulting from contradictory advice is worse than the direct consequences of the attack: it enables future attacks. Why play Keystone Cyber Cops when UK National Technical Authority for such matters, the National Centre for Cyber Security, offers authoritative and well-presented advice on their website?

Our other concern is the unedifying squabbling between spokespeople for governments and suppliers blaming each other for running unsupported software, not paying for support, charging to support unsupported software, and so on, with and security experts weighing in on all sides. To a general public already alarmed by media headlines, finger-pointing creates little confidence that either party is competent or motivated to keep secure the technology on which our lives all now depend. When the supposed “good guys” expend their energy fighting each other, instead of working together to defeat the attackers, it’s hard to avoid the conclusion that we are most definitely doomed. As Columbia University professor Steve Bellovin writes, the question of who should pay to support old software requires broader collaborative thought; in avoiding that debate we are choosing to pay as a society for such security failures.

We would refer those looking for specific advice on dealing with ransomware to the NCSC guidance, which is offered in separate parts for SMEs and home users and enterprise administrators.

Much of NCSC’s advice is made up of things we all know: we should back up our data, patch our systems, and run anti-virus software. Part of RISCS’ remit is to understand why users often don’t follow this advice. Ensuring backups remain uninfected is, unfortunately, trickier than it should be. Ransomware will infect – that is, encrypt – not only the machine it’s installed on but any permanently-connected physical or network drive. This problem ought to be solved by cloud storage, but it can be difficult to find out whether cloud backups will be affected by ransomware, and technical support documentation often simply refers individuals to “your IT support”, even though vendors know few individuals have any. Dropbox is unusually helpful, and provides advice on how to recover from a ransomware attack and how far it can help. Users should be encouraged to read such advice in advance and factor it into backup plans.

There are many reasons why people do not update their software. They may, for example, have had bad experiences in the past that lead them to worry that security updates will fail or leave their system damaged, or incorporate unwanted changes in functionality. Software vendors can help here by rigorously testing updates and resisting the temptation to bundle in new features. IT support staff can help by doing their own tests that allow them to reassure their users that they will help resolve any resulting problems in a timely manner.

In some cases, there are no updates to install. The WannaCry ransomware attack highlighted the continuing use of desktop Windows XP, which Microsoft stopped supporting with security updates in 2014. A few organisations still pay for special support contracts, and Microsoft made an exception for WannaCry by releasing a security patch more widely. Organisations that still have XP-based systems should now investigate to understand why equipment using an unsafe, outdated operating system is still in use. Ideally, the software should be replaced with a more modern system; if that’s not possible the machine should be isolated from network connections. No amount of reminding users to patch their systems or telling them to “be vigilant” will be effective in such cases.


This article also appears on the Research Institute in Science of Cyber Security (RISCS) blog.

Steven Murdoch – Privacy and Financial Security

Probably not too many academic researchers can say this: some of Steven Murdoch’s research leads have arrived in unmarked envelopes. Murdoch, who has moved to UCL from the University of Cambridge, works primarily in the areas of privacy and financial security, including a rare specialty you might call “crypto for the masses”. It’s the financial security aspect that produces the plain, brown envelopes and also what may be his most satisfying work, “Trying to help individuals when they’re having trouble with huge organisations”.

Murdoch’s work has a twist: “Usability is a security requirement,” he says. As a result, besides writing research papers and appearing as an expert witness, his past includes a successful start-up. Cronto, which developed a usable authentication device, was acquired by VASCO, a market leader in authentication and is now used by banks such as Commerzbank and Rabobank.

Developing the Cronto product was, he says, an iterative process that relied on real-world testing: “In research into privacy, if you build unusable system two things will go wrong,” he says. “One, people won’t use it, so there’s a smaller crowd to hide in.” This issue affects anonymising technologies such as Mixmaster and Mixminion. “In theory they have better security than Tor but no one is using them.” And two, he says, “People make mistakes.” A non-expert user of PGP, for example, can’t always accurately identify which parts of the message are signed and which aren’t.

The start-up experience taught Murdoch how difficult it is to get an idea from research prototype to product, not least because what works in a small case study may not when deployed at scale. “Selling privacy remains difficult,” he says, noting that Cronto had an easier time than some of its forerunners since the business model called for sales to large institutions. The biggest challenge, he says, was not consumer acceptance but making a convincing case that the predicted threats would materialise and that a small company could deliver an acceptable solution.

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Jens Groth – Non-interactive zero knowledge proofs, efficient enough to be used in practice

The UCL information security group’s Jens Groth, a cryptographer, is one of 17 UCL researchers who have been awarded a Starting Grant by the European Research Council. The five-year grant will fund his work on the cryptographic building block known as “zero-knowledge proofs”, a widely applicable technique that underpins both security and trust. ERC Starting Grants are intended to support up-and-coming research leaders who are beginning to set up a research team and conduct independent research. Groth’s focus is on making zero- knowledge proofs more efficient so that they can become cheap enough to become a commonly used, standard security technology. Groth is also the recipient of a second grant from the Engineering and Physical Sciences Research Council to fund his work on another related topic, structure-preserving pairing-based cryptography.

“My line of thinking,” says Groth, “is that there’s been a lot of research into zero-knowledge proofs, but I don’t know of any groups taking entire systems from theory through to very practical implementations. I am hoping to build a group that will cover this entire span, and by covering it thoroughly get some very significant gains in efficiency.” Covering that entire spectrum from the purely abstract to the built system is important, he says, because “Practice can influence theory and give us some insight into what we should be looking at. Also, when you start implementing things, lots of surprising discoveries can come up.”

Unlike other types of cryptographic tools, such as public key cryptography, used in such widely used mass-market applications as SSL (used to secure data passed over the Web while in transit), Groth notes that zero-knowledge proofs are more likely to be a behind-the-scenes technology that end users will never touch directly.

“It will be hidden inside the system,” he says. “The main properties we want are completeness, soundness – and zero-knowledge.” Completeness means the prover can convince the verifier when a statement is true. Soundness means the prover cannot convince the verifier when the statement is false. Finally, zero-knowledge means that there is no leakage of information even if the prover is interacting with a fraudulent verifier.

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Nicolas Courtois – Algebraic cryptanalysis is not the best way to break something, but sometimes it is the only option

Nicolas Courtois, a mathematician and senior lecturer in computer science at UCL, working with Daniel Hulme and Theodosis Mourouzis, has won the 2012 best paper award from the International Academy, Research, and Industry Association for their work on using SAT solvers to study various problems in algebra and circuit optimization. The research was funded by the European Commission under the FP7 project number 242497, “Resilient Infrastructure and Building Security (RIBS)” and by the UK Technology Strategy Board under project 9626-58525. The paper, Multiplicative Complexity and Solving Generalized Brent Equations with SAT Solvers, was presented at Computation Tools 2012, the third International Conference on Computational Logics, Algebras, Programming, Tools, and Benchmarking, held in Nice, France in July.

SAT (short for “satisfiability”) solvers are algorithms used to analyse logical problems composed of multiple statements such as “A is true OR not-B is true or C is true” for the purpose of determining whether the whole system can be true – that is, whether all the statements it’s composed of can be satisfied. SAT solvers also are used to determine how to assign the variables to make the set of statements true. In 2007, Bard and Courtois realised they could be used to test the security of cryptographic functions and measure their complexity, and today they are important tools in cryptanalysis; they have already been used for a long time in other applications such as verifying hardware and software. In this particular paper, Courtois, Hulme, and Mourouzis focused on optimising S-boxes for industrial block ciphers; the paper reports the results of applying their methodology to the PRESENT and GOST block ciphers. Reducing the complexity and hardware cost of these ciphers is particularly important to build so-called secure implementations of cryptography. These are particularly costly because they need to protect against additional threats such as side-channel attacks, in which the attacker exploits additional information leaked from the physical system – for example, by using an oscilloscope to observe a smart card’s  behaviour.

“It’s more a discovery than an invention,” says Courtois. “One of the amazing things SAT solvers can do is give you proof that something is not true.” The semiconductor industry provides one application of the work in this paper: these techniques promise to provide a way to test whether a circuit has been built with the greatest possible efficiency by proving that the chip design uses the smallest possible number of logic gates.

“You’ll get optimal designs and be able to prove they cannot be done better,” he says.

Classical cryptanalysis proceeds by finding approximations to the way a cipher works. Many successful academic attacks have been mounted using such techniques, but they rely on having a relatively large amount of data available for study. That works for large archives of stored data – such as, for example, the communications stored and kept by the Allies after World War II for later cryptanalysis. But in many real-world applications, it is more common to have only very small amounts of data.

“The more realistic scenario is that you’ll just have one or a few messages,” says Courtois. Bluetooth, for example, encrypts only 1,500 bits with a single key. “Most attacks are useless because they won’t work with this quantity of data.” Algebraic cryptanalysis, which he explained in New Frontier in Symmetric Cryptanalysis, an invited talk at Indocrypt 2008, by contrast, is one of the few techniques that can be hoped to work in such difficult situations.

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Sarah Meiklejohn – Security and Cryptography

Sarah Meiklejohn As a child, Sarah Meiklejohn thought she might become a linguist, largely because she was so strongly interested in the work being done to decode the ancient Greek writing systems Linear A and Linear B.

“I loved all that stuff,” she says. “And then I started doing mathematics.” At that point, with the help of Simon Singh’s The Code Book, she realised the attraction was codebreaking rather than human languages themselves. Simultaneously, security and privacy were increasingly in the spotlight.

“I’m a very private person, and so privacy is near and dear to my heart,” she says. “It’s an important right that a lot of people don’t seem interested in exercising, but it’s still a right. Even if no one voted we would still agree that it was important for people to be able to vote.”

It was during her undergraduate years at Brown, which included a fifth-year Masters degree, that she made the transition from mathematics to cryptography and began studying computer science. She went on to do her PhD at the University of California at San Diego. Her appointment at UCL, which is shared between the Department of Computer Science and the Department of Crime Science, is her first job.

Probably her best-known work is A Fistful of Bitcoins: Characterizing Payments Among Men with No Names (PDF), written with Marjori Pomarole, Grant Jordan, Kirill Levchenko, Damon McCoy, Geoffrey M. Voelker, and Stefan Savage and presented at USENIX 2013, which studied the question of how much anonymity bitcoin really provides.

“The main thing I was trying to focus on in that paper is what bitcoin is used for,” she says. The work began with buying some bitcoin (in 2012, at about £3 each), and performing some transactions with them over a period of months. Using the data collected this way allowed her to uncover some “ground truth” data.

“We developed these clustering techniques to get down to single users and owners.” The result was that they could identify which addresses belonged to which exchanges and enabled them to get a view of what was going on in the network. “So we could say this many bitcoins passed through this exchange per month, or how many were going to underground services like Silk Road.”

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George Danezis – Smart grid privacy, peer-to-peer and social network security

“I work on technical aspects of privacy,” says George Danezis, a reader in security and privacy engineering at UCL and part of the Academic Centre of Excellence in Cyber Security Research (ACE-CSR). There are, of course, many other limitations: regulatory, policy, economic. But, he says, “Technology is the enabler for everything else – though you need everything else for it to be useful.” Danezis believes providing privacy at the technology level is particularly important as it seems clear that both regulation and the “moralising” approach (telling people the things they shouldn’t do) have failed.

There are many reasons why someone gets interested in researching technical solutions to intractable problems. Sometimes the motivation is to eliminate a personal frustration; other times it’s simply a fascination with the technology itself. For Danezis, it began with other people.

“I discovered that a lot of the people around me could not use technology out of the box to do things personally or collectively.” For example, he saw NGOs defending human rights worry about sending an email or chatting online, particularly in countries hostile to their work. A second motivation had to do with timing: when he began work it wasn’t yet clear that the Internet would develop into a medium anyone could use freely to publish stories. That particular fear has abated, but other issues such as the need for anonymous communications and private data sharing are still with us.

“Without anonymity we can’t offer strong privacy,” he says.

Unlike many researchers, Danezis did not really grow up with computers. He spent his childhood in Greece and Belgium, and until he got Internet access at 16, “I had access only to the programming books I could find in an average Belgian bookshop. There wasn’t a BBC Micro in every school and it was difficult to find information. I had one teacher who taught me how to program in Logo, and no way of finding more information easily.” Then he arrived at Cambridge in 1997, and “discovered thousands of people who knew how to do crazy stuff with computers.”

Danezis’ key research question is, “What functionality can we achieve while still attaining a degree of hard privacy?” And the corollary: at what cost in complexity of engineering? “We can’t just say, let’s recreate the whole computer environment,” he said. “We need to evolve efficiently out of today’s situation.”

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Gianluca Stringhini – Cyber criminal operations and developing systems to defend against them

Gianluca Stringhini’s research focuses on studying cyber criminal operations and developing systems to defend against them.

Such operations tend to follow a common pattern. First the criminal operator lures a user into going to a Web site and tries to infect them with malware. Once infected, the user is joined to a botnet. From there, the user’s computer is instructed to perform malicious activities on the criminal’s behalf. Stringhini, whose UCL appointment is shared between the Department of Computer Science and the Department of Security and Crime Science, has studied all three of these stages.

Stringhini, who is from Genoa, developed his interest in computer security at college: “I was doing the things that all college students are doing, hacking, and breaking into systems. I was always interested in understanding how computers work and how one could break them. I started playing in hacking competitions.”

At the beginning, these competitions were just for fun, but those efforts became more serious when he arrived in 2008 at UC Santa Barbara, which featured one of the world’s best hacking teams, a perennial top finisher in Defcon’s Capture the Flag competition. It was at Santa Barbara that his interest in cyber crime developed, particularly in botnets and the complexity and skill of the operations that created them. He picked the US after Christopher Kruegel, whom he knew by email, invited him to Santa Barbara for an internship. He liked it, so he stayed and did a PhD studying the way criminals use online services such as social networks

“Basically, the idea is that if you have an account that’s used by a cyber criminal it will be used differently than one used by a real person because they will have a different goal,” he says. “And so you can develop systems that learn about these differences and detect accounts that are misused.” Even if the attacker tries to make their behaviour closely resemble the user’s own, ultimately spreading malicious content isn’t something normal users intend to do, and the difference is detectable.

This idea and Stringhini’s resulting PhD research led to his most significant papers to date.

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