When Convenience Creates Risk: Taking a Deeper Look at Security Code AutoFill on iOS 12 and macOS Mojave

A flaw in Apple’s Security Code AutoFill feature can affect a wide range of services, from online banking to instant messaging.

In June 2018, we reported a problem in the iOS 12 beta. In the previous post, we discussed the associated risks the problem creates for transaction authentication technology used in online banking and elsewhere. We described the underlying issue and that the risk will carry over to macOS Mojave. Since our initial reports, Apple has modified the Security Code AutoFill feature, but the problem is not yet solved.

In this blog post, we publish the results of our extended analysis and demonstrate that the changes made by Apple mitigated one symptom of the problem, but did not address the cause. Security Code AutoFill could leave Apple users in a vulnerable position after upgrading to iOS 12 and macOS Mojave, exposing them to risks beyond the scope of our initial reports.

We describe four example attacks that are intended to demonstrate the risks stemming from the flawed Security Code AutoFill, but intentionally omit the detail necessary to execute them against live systems. Note that supporting screenshots and videos in this article may identify companies whose services we’ve used to test our attacks. We do not infer that those companies’ systems would be affected any more or any less than their competitors.

Flaws in Security Code AutoFill

The Security Code AutoFill feature extracts short security codes (e.g., a one-time password or OTP) from an incoming SMS and allows the user to autofill that code into a web form, webpage, or app when authenticating. This feature is meant to provide convenience, as the user no longer needs to memorize and re-enter a code in order to authenticate. However, this convenience could create risks for the user.

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Will new UK rules reduce the harm of push-payment fraud?

On Friday’s Rip off Britain I’ll be talking about new attempts by UK banks to prevent fraud, and the upcoming scheme for reimbursing the victims. While these developments have the potential to better protect customers, the changes could equally leave customers in a more vulnerable situation than before. What will decide between these two extremes is how well designed will be the rules surrounding these new schemes.

The beginning of this story is September 2016, when the consumer association – Which? – submitted a super-complaint to the UK Payment System Regulator (PSR) regarding push payment fraud – where a customer is tricked into transferring money into a criminal’s account. Such bank transfers are known as push payments because they are initiated by the bank sending the money, as opposed to pull payments, like credit and debit cards, where it is the receiving bank that starts the process. Banks claim that since the customer was involved in the process, they “authorised” the transaction, and so under UK and EU law, the customer is not entitled to a refund. I’ve argued that this interpretation doesn’t match any reasonable definition of the word “authorised” but nevertheless the term “authorised push payment scams” seems to have stuck as the commonly used terminology for this type of fraud, I’m sure much to the banks’ delight.

The Which? super-complaint asked for banks to be held liable for such frauds, and so reimburse the victims unless the bank can demonstrate the customer has acted with gross negligence. Which? argued that this approach would protect the customers from a fraud that exists as a consequence of bank design decisions, and provides banks with both a short-term incentive to prevent frauds that they can stop, as well as a medium-to-long term incentive for the banks to enhance payment systems to be resistant to fraud. The response from the PSR was disappointing, recognising that banks should do more, but rejecting the recommendation to hold banks liable for this fraud and requesting only that the banks collect more data. Nevertheless, the data collected proved useful in understanding the scale of the problem – £236 million stolen from over 42,000 victims in 2017, with banks only being able to recover 26% of the losses. This revelation led to Parliament asking difficult questions of the PSR.

The PSR’s alternative to holding banks liable for push payment fraud is for victims to be reimbursed if they can demonstrate they have acted with an appropriate level of care and that the bank has not. The precise definition of each level of care was a subject of consultation, and will now be decided by a steering group consisting of representatives of the banking industry and consumers. In my response to this consultation, I explained my reasons for recommending that banks be liable for fraud, including that fairly deciding whether customers met a level of care is a process fraught with difficulties. This is particularly the case due to the inequality in power between a bank and its customer, and that taking a banking dispute to court is ruinously expensive for most people since the option of customers spreading the cost through collective actions was removed from the Financial Services Act. More generally, banks – as the designers of payment systems and having real-world understanding of their use – have the greatest capacity to mitigate the risks these systems introduce.

Nevertheless, if the rules for the reimbursement scheme are set up well, it would be a substantial improvement over the current situation. On the other hand, if the process is bad then it could entrench the worst of current practices. Because the PSR has decided that reimbursement should depend on compliance to a level of care, my response also included what should be the process for defining these levels, and for adjudicating disputes.

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Security code AutoFill: is this new iOS feature a security risk for online banking?

A new feature for iPhones in iOS 12 – Security Code AutoFill – is supposed to improve the usability of Two Factor Authentication but could place users at risk of falling victim to online banking fraud.

Two Factor Authentication (2FA), which is often referred to as Two Step Verification, is an essential element for many security systems, especially those online and accessed remotely. In most cases, it provides extended security by checking if the user has access to a device. In SMS-based 2FA, for example, a user registers their phone number with an online service. When this service sees a login attempt for the corresponding user account, it sends a One Time Password (OTP), e.g. four to six digits, to the registered phone number. The legitimate user then receives this code and is able to quote it during the login process, but an impersonator won’t.

In a recent development by Apple, announced at its developer conference WWDC18, they are set to automate this last step to improve user experience with 2FA with a new feature that is set to be introduced to iOS in version 12. The Security Code AutoFill feature, currently available to developers in a beta version, will allow the mobile device to scan incoming SMS messages for such codes and suggest them at the top of the default keyboard.

Description of new iOS 12 Security Code AutoFill feature (source: Apple)

Currently, these SMS codes rely on the user actively switching apps and memorising the code, which can take a couple of seconds. Some users deploy alternative try strategies such as memorising the code from the preview banner and hastily typing it down. Apple’s new iOS feature will require only a single tap from the user. This will make the login process faster and less error prone, a significant improvement to the usability of 2FA. It could also translate into an increased uptake of 2FA among iPhone users.

Example of Security Code AutoFill feature in operation on iPhone (source: Apple)

If users synchronise SMS with their MacBook or iMac, the existing Text Message Forwarding feature will push codes from their iPhone and enable Security Code AutoFill in Safari.

Example of Security Code AutoFill feature synchronised with macOS Mojave (source: Apple)

Reducing friction in user interaction to improve technology uptake for new users, and increase the usability and satisfaction for existing users, is not a new concept. It has not only been discussed in academia at length but is also a common goal within industry, e.g. in banking. This is evident in how the financial and payment industry has encouraged contactless (Near Field Communication – NFC) payments, which makes transactions below a certain threshold much quicker than traditional Chip and PIN payments.

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Incentives in Security Protocols

The 2018 edition of the International Security Protocols Workshop took place last week. The theme this year was “fail-safe and fail-deadly concepts in protocol design”.

One common theme at this year’s workshop is that of threat models and incentives, which is covered by the majority of accepted papers. One of these is our (Sarah Azouvi, Alexander Hicks and Steven Murdoch) submission – Incentives in Security Protocols. The aim of the paper is to discuss how incentives can be considered and incorporated in the security of systems. In line with the given theme, the focus is on fail-safe and fail-deadly cases which we look at for the cases of the EMV protocol, consensus in cryptocurrencies, and non-economic systems such as Tor. This post will summarise the main ideas laid out in the paper.

Fail safe, fail deadly and people

Systems can fail, which requires some thought by system designers to account for these failures. From this setting comes the idea behind fail safe protocols which are such that even if the protocol fails, the failure can be dealt with or the protocol can be aborted to limit damage. The idea of a fail deadly setting is an extension of this where failure is defended against through deterrence, as in the case of nuclear deterrence (sometimes a realistic case).

Human input often plays a role in the use of the system, particularly when decisions are required as in fail safe and fail deadly instances. These decisions are then made according to incentives which can aligned to make the system robust to failure. For a fail deadly alignment, this means that a person in position to prevent system failure will be harmed by the failure. In the fail safe case, the innocent parties should be protected from the consequences of system failure. The two concepts are really two sides of the same coin that assigns liability.

It is often said that people are the weakest link in security, but that is an easy excuse for broken protocols. If security incentives are aligned properly, then humans are the strongest link.

The EMV protocol, adding incentives after the fact

As a first example, we consider the case of the EMV protocol, which is used for the majority of smart card payments worldwide, as well as smartphone and card-based contactless payment. Over the years, many vulnerabilities have been identified and removed. Fraud still exists however, due not to unexpected protocol vulnerabilities but to decisions made by banks (e.g., omitting the ability for cards to produce digital signatures), merchants (e.g., omitting PIN verification) and payment networks not sending transactions details back to banks. These are intentional choices, aiming to saves costs and cut transaction times but make fraud harder to detect.

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A witch-hunt for trojans in our chips

A Hardware Trojan (HT) is a malicious modification of the circuitry of an integrated circuit.

 

A malicious chip can make a device malfunction in several ways. It has been rumored that a hardware trojan implanted in a Syrian air-defense radar caused it to stop operating during an airstrike, thus instantly minimizing the country’s situational awareness and threat response capabilities. In other settings, hardware trojans may leak encryption keys or other secrets, or even generate weak keys that can be easily recovered by the adversary.

This article introduces a new trojan-resilient architecture, discusses its motivation and outlines how it differs from existing solutions. The full paper (Vasilios MavroudisAndrea CerulliPetr Svenda, Dan CvrcekDusan Klinec, George Danezis) has been presented in several academic and industrial venues including DEF CON 25, and ACM Conference on Computer and Communications Security 2017.

The Challenge of Detecting HT

Judging from the abundance of governmental, industrial and academic projects concerned with the prevention and the detection of hardware trojans, there is a consensus regarding the severity of the threat and it’s not taken lightly. DARPA has launched the “Integrity and Reliability of Integrated Circuits“ program aiming to develop techniques for the detection of malicious circuitry. The Intelligence Advanced Research Projects Activity funded a project aiming to redesign the fabrication of integrated circuits, while various other initiatives are currently undergoing (e.g., the COST Action project on “Trustworthy Manufacturing and Utilization of Secure Devices” and the DoD Trusted Foundry program). In addition to these, there are numerous other industrial and academic projects proposing new trojan detection techniques every year, only to be circumvented by follow up work.

But do Hardware Trojans exist?

Ironically, until now there have been no cases where malicious circuitry was detected in military-grade or even commercial chips. With nothing more than rumors to hint about hardware trojans (in places other than academic lab benches), one cannot but question their existence. In other words, is HT design and insertion too complex to be practical, or do our detection tools fail to detect the malicious circuitry embedded in the chips around us?

It could be that both are true: hardware trojans do not exist (yet) as malicious actors are focusing on other aspects of the hardware that are easier to compromise. In all cases where trojans were discovered, the erroneous behavior was traced to the chip’s firmware and not its circuitry. Interestingly, in the vast majority of those incidents the security flaws were attributed to honest fabrication mistakes (e.g., manufacturer failing to disable a testing interface).

Intentional vs. Unintentional Errors

It is safe to always assume that an IC will fail in the worst possible way, at the worst possible time (see Syrian airdefense incident). This “crash n’ burn” approach is common in critical systems (e.g., airplanes, satellites, dams), where any divergence from normal operation will result in an irrecoverable failure of the whole system.

To mitigate the risk, critical system designers employ redundancy techniques to eliminate single points of failure and thus make their setups resilient to faults. A common example are triple-redundant systems used in autopilots. Those systems employ three identical chips sourced from disjoint supply chains and replicate all the navigation computations across them. This allows the system to both tolerate a misbehaving chip and detect its presence.

It is noteworthy, that those systems do not consider the cause of the chip malfunction, and simply assume that they fail in the worst possible way. Following from this, a malicious chip is not significantly different from a defective one. After all, any adversary sophisticated enough to design and insert a hardware trojan is capable of making it indistinguishable from honest manufacturing errors. Similarly, from an operational perspective it makes little sense to distinguish between trojans in the circuitry and trojans in the firmware as the risk they pose for the system is identical.

Distributing Trust for Resilience

Given that it is impossible to achieve 100% detection rates of hardware trojans and errors, it is important that our devices maintain their security properties even in their presence. Our work introduces a new high-level device architecture that is resilient to both. In its core, it uses a redundancy-based architecture and secret-sharing protocols to distribute all secrets and computations among multiple chips. Hence, unless all chips are compromised by the same adversary, the security of the system remains intact. A key point is that those chips should originate from disjoint supply chains. This is to minimize the risk of the same adversary compromising more than one chips. To evaluate its practicality in real-life applications, we built a Hardware Security Module (HSM) that performs standard cryptographic operations (e.g., key generation, decryption, signing) at a very high rate. HSMs are commonly used in operations where security is critical, and an increased transaction throughput is needed (e.g., banking, certification Authorities). A demonstration is shown in the video above, and further details are on our website. Finally, our work can be easily combined with all existing detection and prevention techniques to further decrease the likelihood of compromises.

Liability for push payment fraud pushed onto the victims

This morning, BBC Rip Off Britain focused on push payment fraud, featuring an interview with me (starts at 34:20). The distinction between push and pull payments should be a matter for payment system geeks, and certainly isn’t at the front of customers’ minds when they make a payment. However, there’s a big difference when there’s fraud – for online pull payments (credit and debit card)  the bank will give the victim the money back in many situations; for online push payments (Faster Payment System and Standing Orders) the full liability falls on the party least able to protect themselves – the customer.

The banking industry doesn’t keep good statistics about push payment fraud, but it appears to be increasing, with Which receiving reports from over 650 victims in the first two weeks of November 2016, with losses totalling over £5.5 million. Today’s programme puts a human face to these statistics, by presenting the case of Jane and Steven Caldwell who were defrauded of over £100,000 from their Nationwide and NatWest accounts.

They were called up at the weekend by someone who said he was working for NatWest. To verify that this was the case, Jane used three methods. Firstly, she checked caller-ID to confirm that the number was indeed the bank’s own customer helpline – it was. Secondly, she confirmed that the caller had access to Jane’s transaction history – he did. Thirdly, she called the bank’s customer helpline, and the caller knew this was happening despite the original call being muted.

Convinced by these checks, Jane transferred funds from her own accounts to another in her own name, having been told by the caller that this was necessary to protect against fraud. Unfortunately, the caller was a scammer. Experts featured on the programme suspect that caller-ID was spoofed (quite easy, due to lack of end-to-end security for phone calls), and that malware on Jane’s laptop allowed the scammer to see transaction history on her screen, as well as to listen to and see her call to the genuine customer helpline through the computer’s microphone and webcam. The bank didn’t check that the name Jane gave (her own) matched that of the recipient account, so the scammer had full access to the transferred funds, which he quickly moved to other accounts. Only Nationwide was able to recover any money – £24,000 – leaving Jane and Steven over £75,000 out of pocket.

Neither bank offered Jane and Steven a refund, because they classed the transaction as “authorised” and so falling into one of the exceptions to the EU Payment Services Directive requirement to refund victims of fraud (the other exception being if the bank believed the customer acted either with gross negligence or fraudulently). The banks argued that their records showed that the customer’s authentication device was used and hence the transaction was “authorised”. In the original draft of the Payment Services Directive this argument would not be sufficient, but as a result of concerted lobbying by Barclays and other UK banks for their records to be considered conclusive, the word “necessarily” was inserted into Article 72, and so removing this important consumer protection.

“Where a payment service user denies having authorised an executed payment transaction, the use of a payment instrument recorded by the payment service provider, including the payment initiation service provider as appropriate, shall in itself not necessarily be sufficient to prove either that the payment transaction was authorised by the payer or that the payer acted fraudulently or failed with intent or gross negligence to fulfil one or more of the obligations under Article 69.”

Clearly the fraudulent transactions do not meet any reasonable definition of “authorised” because Jane did not give her permission for funds to be transferred to the scammer. She carried out the transfer because the way that banks commonly authenticate themselves to customers they call (proving that they know your account details) was unreliable, because the recipient bank didn’t check the account name, because bank fraud-detection mechanisms didn’t catch the suspicious nature of the transactions, and because the bank’s authentication device is too confusing to use safely. When the security of the payment system is fully under control of the banks, why is the customer held liable when a person acting with reasonable care could easily do the same as Jane?

Another question is whether banks do enough to recover funds lost through scams such as this. The programme featured an interview with barrister Gideon Roseman who quickly obtained court orders allowing him to recover most of his funds lost through a similar scam. Interestingly a side-effect of the court orders was that he discovered that his bank, Barclays, waited more than 24 hours after learning about the fraud before they acted to stop the stolen money being transferred out. After being caught out, Barclays refunded Gideon the affected funds, but in cases where the victim isn’t a barrister specialising in exactly these sorts of disputes, do the banks do all they could to recover stolen money?

In order to give banks proper incentives to prevent push payment fraud where possible and to recover stolen funds in the remainder of cases, Which called for the Payment Systems Regulator to make banks liable for push payment fraud, just as they are for pull payments. I agree, and expect that if this were the case banks would implement innovative fraud prevention mechanisms against push payment fraud that we currently only see for credit and debit transactions. I also argued that in implementing the revised Payment Service Directive, the European Banking Authority should require banks provide evidence that a customer was aware of the nature of the transaction and gave informed consent before they can hold the customer liable. Unfortunately, both the Payment Systems Regulator, and the European Banking Authority conceded to the banking industry’s request to maintain the current poor state of consumer protection.

The programme concluded with security advice, as usual. Some was actively misleading, such as the claim by NatWest that banks will never ask customers to transfer money between their accounts for security reasons. My bank called me to transfer money from my current account to savings account, for precisely this reason (I called them back to confirm it really was them). Some advice was vague and not actionable (e.g. “be vigilant” – in response to a case where the victim was extremely cautious and still got caught out). Probably the most helpful recommendation is that if a bank supposedly calls you, wait 5 minutes and call them back using the number on a printed statement or card, preferably from a different phone. Alternatively stick to using cheques – they are slow and banks discourage their use (because they are expensive for them to process), but are much safer for the customer. However, such advice should not be considered an alternative to pushing liability back where it belongs – the banks – which will not only reduce fraud but also protect vulnerable customers.

Underground abraCARDabra: Understanding carding forums

Paying for dinner? A taxi ride? A tropical drink? Sure. Swipe or tap your card and it is done. Convenient. Payment cards make it easy for us to make payments at “brick-and-mortar” locations and online marketplaces. However, they are also attractive targets for cybercriminals seeking to steal funds from the accounts linked to payment cards, as seen in this recent high-profile theft of credit cards affecting more than 1,000 hotels, for instance.

Theft of payment card information via phishing, skimming, or hacking, is usually the first step in the chain of payment card fraud. Other steps include sales, validation, and monetisation of the stolen data. These illicit deals are aided by underground online forums where cybercriminals actively trade stolen credit card information. To tackle payment card fraud, it is therefore important to understand the characteristics of these forums and the activity of miscreants using them. In our paper, presented at the 2017 APWG Symposium on Electronic Crime Research (eCrime2017), we analyse and discuss the characteristics of underground carding forums. We focus on the available products and prices, characteristics of sellers, and features of the forums. We won the Best Paper Award at eCrime2017.

Products

The main products available on carding forums are credit card numbers, dumps, and fullz. Credit card numbers comprise the information actually printed on credit cards, that is, cardholder name, card number (16 digits on most cards), expiry date, and the security code on the back of the card (usually 3 digits).

Dumps comprise stolen information from the tracks of magnetic stripe of a credit card. Dumps are usually obtained via skimmers. Skimmers are devices attached to Automated Teller Machines (ATMs) and Point of Sale (POS) terminals by miscreants to steal data from unsuspecting victims. Afterwards, the miscreants create clones of the skimmed credit cards and monetise the clones, for instance, by making illicit purchases with them.

Fullz contain further information about the cardholder. In other words, fullz usually comprise information printed on the card plus additional information such as bank account information, cardholder’s date of birth, Social Security number, etc.

Sellers

Generally, there are several types of participants on carding forums: sellers, buyers, intermediaries, mules, administrators, and others. These roles are not mutually exclusive; sellers may simultaneously be buyers. In this study, we focus on sellers since they come before buyers in the fraud chain.

Our approach

We studied previous work on underground marketplaces and forums, and derived the following hypotheses from the insights gained. We then searched for names of carding forums, found 25 names, and collected data from 5 active forums. We then tested the hypotheses on the data.

Hypothesis 1. Prices of fullz (credit card numbers and additional cardholder information) are higher than prices of credit card numbers.
Hypothesis 2. A small number of traders are responsible for a large
proportion of traffic.
Hypothesis 3. Most traders sell only one product type (that is, they are specialised).
Hypothesis 4. Specialised traders sell their products at lower prices than unspecialised traders.
Hypothesis 5. Carding forums have working reputation systems that are as sophisticated as those of legal marketplaces (for instance, eBay).
Hypothesis 6. The vast majority of actors do not operate on more than
one forum.

Summary of findings

Our analyses confirmed Hypothesis 1, Hypothesis 2, and Hypothesis 6. In other words, prices of fullz are indeed higher than prices of credit card numbers (credit card numbers: mean = $10.08, median = $10.00; fullz: mean = $31.82, median = $30.00). Also, a small number of traders are responsible for a large proportion of traffic. Finally, most sellers focus their efforts on a single forum, as expected.

Hypothesis 4 was partially rejected, while Hypothesis 3 and Hypothesis 5 were completely rejected. In other words, specialised sellers do not always sell their products at lower prices than the unspecialised ones, most sellers advertise more than one type of product, and most of the carding forums under study do not have working reputation systems that are as elaborate as those of legitimate online marketplaces.

In conclusion, dumps and fullz are relatively expensive; they are more than three times as expensive as credit card numbers. This may be due to the effort needed to obtain or monetise the data, the amount of available information, or differing supply and demand. Sellers have varying success. Even though some sellers complete hundreds of transactions, most sellers do not succeed in selling anything. This means that the trading sections of the forums are profitable distribution channels for high-profile actors. Finally, specialisation is not a key characteristic of sellers, not even of high-profile sellers.

Further details can be found in the full paper All Your Cards Are Belong To Us: Understanding Online Carding Forums, by Andreas Haslebacher, Jeremiah Onaolapo, and Gianluca Stringhini.

Online security won’t improve until companies stop passing the buck to the customer

It’s normally in the final seconds of a TV or radio interview that security experts get asked for advice for the general public – something simple, unambiguous, and universally applicable. It’s a fair question, and what the public want. But simple answers are usually wrong, and can do more harm than good.

For example, take the UK government’s Cyber Aware scheme to educate the public in cybersecurity. It recommends individuals choose long and complex passwords made out of three words. The problem with this advice is that the resulting passwords are hard to remember, especially as people have many passwords and use some infrequently. Consequently, they will be tempted to use the same password on multiple websites.

Password re-use is far more of a security problem than insufficiently complex passwords, so advice that doesn’t help people manage multiple passwords does more harm than good. Instead, I would recommend remembering your most important passwords (like banking and email), and store the rest in a password manager. This approach isn’t perfect or suitable for everyone, but for most people, it will improve their security.

Advice unfit for the real world

Cyber Aware also tells people not to write down their passwords, or let anyone else know them – banks require the same thing. But we know that people commonly share their banking credentials with family, for legitimate reasons. People also realise that writing down passwords is a pretty good approach if you’re only worried about internet hackers, rather than people who can get close to you to see the written notes. Security advice that doesn’t stand up to scrutiny or doesn’t fit with people’s lives will be ignored – and will discredit the organisation offering it.

Because everyone’s situation is different, good security advice should include helping people to understand what risks they should be worried about, and to take steps that mitigate these risks. This advice doesn’t have to be complicated. Teen Vogue published a tutorial on how to select and configure a secure messaging tool, which very sensibly explains that if you are more worried about invasions of privacy from people who can get their hands on your phone, you should make different choices than if you are just concerned about, for example, companies spying on you.

The Teen Vogue article was widely praised by security experts, in stark contrast to an article in The Guardian that made the eye-catching claim that encrypted messaging service WhatsApp is insecure, without making clear that this only applies in an obscure and extremely unlikely set of circumstances.

Zeynep Tufekci, a researcher studying the effects of technology on society, reported that the article was exploited to legitimise misleading advice given by the Turkish government that WhatsApp is unsafe, resulting in human rights activists using SMS instead – which is far easier for the government to censor and monitor.

The Turkish government’s “security advice” to move from WhatsApp to less secure SMS was clearly aimed more at assisting its surveillance efforts than helping the activists to whom the advice was directed. Another case where the advice is more for the benefit of the organisation giving it is that of banks, where the terms and conditions small print gives incomprehensible security advice that isn’t true security advice, instead merely a legal technique to allow the banks wiggle room to refuse to refund victims of fraud.

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Strong Customer Authentication in the Payment Services Directive 2

Within the European Union, since 2007, banks are regulated by the Payment Services Directive. This directive sets out which types of institutions can offer payment services, and what rules they must follow. Importantly for customers, these rules include in what circumstances a fraud victim is entitled to a refund. In 2015 the European Parliament adopted a substantial revision to the directive, the Payment Services Directive 2 (PSD2), and it will soon be implemented by EU member states. One of the major changes in PSD2 is the requirement for banks to implement Strong Customer Authentication (SCA) for transactions, more commonly known as two-factor authentication – authentication codes based on two or more elements selected from something only the user knows, something only the user possesses, and something the user is. Moreover, the authentication codes must be linked to the recipient and amount of the transaction, which the customer must be made aware of.

The PSD2 does not detail the requirements of Strong Customer Authentication, nor the permitted exemptions to this rule. Instead, these decisions are to be made by the European Banking Authority (EBA) through Regulatory Technical Standards (RTS). As part of the development of these technical standards the EBA opened an initial discussion, to which we submitted a response based on our research on the security usability of banking authentication. Based on the discussion, the EBA produced a consultation paper incorporating a set of draft technical standards. In our response to this consultation paper, included below, we detailed how research both on security usability and banking authentication more broadly should guide the assessment of Strong Customer Authentication. Specifically we point out that there is an incorrect assumption of an inherent tradeoff between security and usability, that for a system to be secure it must be usable, and that evaluation of Strong Customer Authentication systems should be independent, transparent, and follow principles developed from latest research.

False trade-off between security and usability

In the reasoning presented in the consultation paper there is an assumption that a trade-off must be made between security and usability, e.g. paragraph 6 “Finally, the objective of ensuring a high degree of security and safety would suggest that the [European Banking Authority’s] Technical Standards should be onerous in terms of authentication, whereas the objective of user-friendliness would suggest that the [Regulatory Technical Standards] should rather promote the competing aim of customer convenience, such as one-click payments.”

This security/usability trade-off is not inherent to Strong Customer Authentication (SCA), and in fact the opposite is more commonly true: in order for SCA to be secure it must also be usable “because if the security is usable, users will do the security tasks, rather than ignore or circumvent them”. Also, SCA that is usable will make it more likely that customers will detect fraud because they will not have to expend their limited attention on just performing the actions required to make the SCA work. A small subset (10–15%) of participants in some studies reasoned that the fact that a security mechanism required a lot of effort from them meant it was secure. But that is a misconception that must not be used as an excuse for effortful authentication procedures.

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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.

Continue reading Steven Murdoch – Privacy and Financial Security