GetCash from NatWest

Banking security, Security engineering, , ,

It has been four or five months since NatWest launched a new function in its mobile phone app – GetCash. The goal was to allow customers to withdraw cash from NatWest’s ATMs without a debit or credit card. The app receives a six digit code that customers can type into an ATM and get as much as £100 at a time. I am not sure how useful it is as I personally forget my mobile phone more often than my wallet but it appears that some crooks found it very useful indeed.

A news about the service being suspended broke out on 6th of October and it has been covered in BBC Breakfast today. I have several thoughts related to this incident. Continue reading GetCash from NatWest →

Who will screen the screeners?

Legal issues, Politics, Security economics, Security engineering, Security psychology

Last time I flew through Luton airport it was a Sunday morning, and I went up to screening with a copy of the Sunday Times in my hand; it’s non-metallic after all. The guard by the portal asked me to put it in the tray with my bag and jacket, and I did so. But when the tray came out, the newspaper wasn’t there. I approached the guard and complained. He tried to dismiss me but I was politely insistent. He spoke to the lady sitting at the screen; she picked up something with a guilty look sideways at me, and a few seconds later my paper came down the rollers. As I left the screening area, there were two woman police constables, and I wondered whether I should report the attempted theft of a newspaper. As my flight was leaving in less than an hour, I walked on by. But who will screen the screeners?

This morning I once more flew through Luton, and I started to suspect it wouldn’t be the airport’s management. This time the guard took exception to the size of the clear plastic bag holding my toothpaste, mouthwash and deodorant, showing me with glee that it has half a centimetre wider than the official outline on a card he had right to hand. I should mention that I was using a Sainsbury’s freezer bag, a standard item in our kitchen which we’ve used for travel for years. No matter; the guard gleefully ordered me to buy an approved one for a pound from a slot machine placed conveniently beside the belt. (And we thought Ryanair’s threat to charge us a pound to use the loo was just a marketing gimmick.) But what sort of signal do you give to low-wage security staff if the airport merely sees security as an excuse to shake down the public? And after I got through to the lounge and tried to go online, I found that the old Openzone service (which charged by the minute) is no longer on offer; instead Luton Airport now demands five pounds for an hour’s access. So I’m writing this blog post from Amsterdam, and next time I’ll probably fly from Stansted.

Perhaps one of these days I’ll write a paper on “Why Security Usability is Hard”. Meanwhile, if anyone reading this is near Amsterdam on Monday, may I recommend the Amderdam Privacy Conference? Many interesting people will be talking about the ways in which governments bother us. (I’m talking about how the UK government is trying to nobble the Data Protection Regulation in order to undermine health privacy.)

Plaintext Password Reminders

Authentication, Web security, ,

There was a public outcry followed by ICO “making enquiries” when Troy Hunt published a post about Tesco’s plaintext password reminders exactly a month ago.

I wanted to use the reference for a text I was writing last week when someone asked me about online accounts of Companies House. At that moment I said to myself, wait a second. Companies House sends plaintext reminders as well. How strange. I sent a link to a short post to ComputerWorld. They in turn managed to get a statement from Companies House that includes:

“… although it is [Companies House] certified to the ISO 27001 standard and adheres to the government’s Security Policy Framework, it will carry out a review of its systems in order to establish whether there is a threat to companies’ confidential information.” Continue reading Plaintext Password Reminders →

The Perils of Smart Metering

News coverage, Politics, Security economics, Security engineering

Alex Henney and I have decided to publish a paper on smart metering that we prepared in February for the Cabinet Office and for ministers. DECC is running a smart metering project that is supposed to save energy by replacing all Britain’s gas and electricity meters with computerised ones by 2019, and to cost only £11bn. Yet the meters will be controlled by the utilities, whose interest is to maximise sales volumes, so there is no realistic prospect that the meters will save energy. What’s more, smart metering already exhibits all the classic symptoms of a failed public-sector IT project.

The paper we release today describes how, when Ed Milliband was Secretary of State, DECC cooked the books to make the project appear economically worthwhile. It then avoided the control procedures that are mandatory for large IT procurements by pretending it was not an IT project but an engineering project. We have already written on the security economics of smart meters, their technical security, the privacy aspects and why the project is failing.

We managed to secure a Cabinet Office review of the project which came up with a red traffic light – a recommendation that the project be abandoned. However DECC dug its heels in and the project appears to be going ahead. Hey, we did our best. The failure should be evident in time for the next election; just remember, you read it here first.

Chip and Skim: cloning EMV cards with the pre-play attack

Academic papers, Banking security, Hardware & signals, Legal issues, Protocols

November last, on the Eurostar back from Paris, something struck me as I looked at the logs of ATM withdrawals disputed by Alex Gambin, a customer of HSBC in Malta. Comparing four grainy log pages on a tiny phone screen, I had to scroll away from the transaction data to see the page numbers, so I couldn’t take in the big picture in one go. I differentiated pages instead using the EMV Unpredictable Number field – a 32 bit field that’s supposed to be unique to each transaction. I soon got muddled up… it turned out that the unpredictable numbers… well… weren’t. Each shared 17 bits in common and the remaining 15 looked at first glance like a counter. The numbers are tabulated as follows:

F1246E04
F1241354
F1244328
F1247348

And with that the ball started rolling on an exciting direction of research that’s kept us busy the last nine months. You see, an EMV payment card authenticates itself with a MAC of transaction data, for which the freshly generated component is the unpredictable number (UN). If you can predict it, you can record everything you need from momentary access to a chip card to play it back and impersonate the card at a future date and location. You can as good as clone the chip. It’s called a “pre-play” attack. Just like most vulnerabilities we find these days some in industry already knew about it but covered it up; we have indications the crooks know about this too, and we believe it explains a good portion of the unsolved phantom withdrawal cases reported to us for which we had until recently no explanation.

Mike Bond, Omar Choudary, Steven J. Murdoch, Sergei Skorobogatov, and Ross Anderson wrote a paper on the research, and Steven is presenting our work as keynote speaker at Cryptographic Hardware and Embedded System (CHES) 2012, in Leuven, Belgium. We discovered that the significance of these numbers went far beyond this one case.

Continue reading Chip and Skim: cloning EMV cards with the pre-play attack →

Password cracking, part II: when does password cracking matter?

Authentication, Security economics, Security engineering, Web security

Yesterday, I took a critical look at the difficulty of interpreting progress in password cracking. Today I’ll make a broader argument that even if we had good data to evaluate cracking efficiency, recent progress isn’t a major threat the vast majority of web passwords. Efficient and powerful cracking tools are useful in some targeted attack scenarios, but just don’t change the economics of industrial-scale attacks against web accounts. The basic mechanics of web passwords mean highly-efficient cracking doesn’t offer much benefit in untargeted attacks. Continue reading Password cracking, part II: when does password cracking matter? →

Password cracking, part I: how much has cracking improved?

Authentication, News coverage, Security economics, Web security

Password cracking has returned to the news, with a thorough Ars Technica article on the increasing potency of cracking tools and the third Crack Me If You Can contest at this year’s DEFCON. Taking a critical view, I’ll argue that it’s not clear exactly how much password cracking is improving and that the cracking community could do a much better job of measuring progress.

Password cracking can be evaluated on two nearly independent axes: power (the ability to check a large number of guesses quickly and cheaply using optimized software, GPUs, FPGAs, and so on) and efficiency (the ability to generate large lists of candidate passwords accurately ranked by real-world likelihood using sophisticated models). It’s relatively simple to measure cracking power in units of hashes evaluated per second or hashes per second per unit cost. There are details to account for, like the complexity of the hash being evaluated, but this problem is generally similar to cryptographic brute force against unknown (random) keys and power is generally increasing exponentially in tune with Moore’s law. The move to hardware-based cracking has enabled well-documented orders-of-magnitude speedups.

Cracking efficiency, by contrast, is rarely measured well. Useful data points, some of which I curated in my PhD thesis, consist of the number of guesses made against a given set of password hashes and the proportion of hashes which were cracked as a result. Ideally many such points should be reported, allowing us to plot a curve showing the marginal returns as additional guessing effort is expended. Unfortunately results are often stated in terms of the total number of hashes cracked (here are some examples). Sometimes the runtime of a cracking tool is reported, which is an improvement but conflates efficiency with power. Continue reading Password cracking, part I: how much has cracking improved? →

The rush to 'anonymised' data

Academic papers, Legal issues, News coverage, Politics, Privacy technology, Security economics, Security engineering

The Guardian has published an op-ed I wrote on the risks of anonymised medical records along with a news article on CPRD, a system that will make our medical records available for researchers from next month, albeit with the names and addresses removed.

The government has been pushing for this since last year, having appointed medical datamining enthusiast Tim Kelsey as its “transparency tsar”. There have been two consultations on how records should be anonymised, and how effective it could be; you can read our responses here and here (see also FIPR blog here). Anonymisation has long been known to be harder than it looks (and the Royal Society recently issued a authoritative report which said so). But getting civil servants to listen to X when the Prime Minister has declared for Not-X is harder still!

Despite promises that the anonymity mechanisms would be open for public scrutiny, CPRD refused a Freedom of Information request to disclose them, apparently fearing that disclosure would damage security. Yet research papers written using CPRD data will surely have to disclose how the data were manipulated. So the security mechanisms will become known, and yet researchers will become careless. I fear we can expect a lot more incidents like this one.

Analysis of FileVault 2 (Apple's full disk encryption)

Academic papers, Authentication, Cryptology, Useful software

With the launch of Mac OS X 10.7 (Lion), Apple has introduced a volume encryption mechanism known as FileVault 2.

During the past year Joachim Metz, Felix Grobert and I have been analysing this encryption mechanism. We have identified most of the components in FileVault 2’s architecture and we have also built an open source tool that can read volumes encrypted with FileVault 2. This tool can be useful to forensic investigators (who know the encryption password or recovery token) that need to recover some files from an encrypted volume but cannot trust or load the MAC OS that was used to encrypt the data. We have also made an analysis of the security of FileVault 2.

A few weeks ago we have made public this paper on eprint describing our work. The tool to recover data from encrypted volumes is available here.

Source Ports in ARF Reports

Security engineering

Long time readers may recall my posts from Jan 2010 about the need for security logging to include source port numbers — because of the growth of ‘Carrier Grade NAT’ (CGN) systems that share one IPv4 address between hundreds, possibly thousands, of users. These systems are widely used by the mobile companies and the ‘exhaustion‘ of IPv4 address space will lead to many other ISPs deploying them.

A key impact of CGNs is that if you want to trace back “who did that” you may need to have recorded not only an IP address and an accurate timestamp, but also to be able to provide the source port of the connection. Failure to provide the source port will mean that an ISP using CGN will not be able to do any tracing, because they will be unable to distinguish between hundreds of possible perpetrators. In June 2011 the IETF published an RFC (6302) which sets out chapter and verse for this issue and sets out Best Practice for security logging systems.

Earlier this year, at the M3AAWG meeting in San Francisco, I talked with the people who have developed the Abuse Reporting Format (ARF). The idea of ARF is that abuse reports will be in standard format — allowing the use of automation at both sender and receiver. Unfortunately ARF didn’t include a field for the source port….

… but it does now, because RFC 6692 has recently been published. My name is on it, but in reality all of the work on it that mattered was done by Murray Kucherawy who wrote the initial draft, who has tweaked the text to address working group concerns and who has guided it through the complexities of the IETF process. Thanks to Murray, the mechanisms for dealing with abuse have now become just a little bit better.