Posts filed under 'Protocols

Feb 16, '12

Three Paper Thursday is an experimental new feature in which we highlight research that group members find interesting.

When new technologies become popular, we privacy people are sometimes miffed that nobody asked for our opinions during the design phase. Sometimes this leads us to make sweeping generalisations such as “only use the Cloud for things you don’t care about protecting” or “Facebook is only for people who don’t care about privacy.” We have long accused others of assuming that the real world is incompatible with privacy, but are we guilty of assuming the converse?

On this Three Paper Thursday, I’d like to highlight three short papers that challenge these zero-sum assumptions. Each is eight pages long and none requires a degree in mathematics to understand; I hope you enjoy them.

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Jan 25, '12

Earlier this month, I blogged about monitoring password-guessing attacks on a server, via a patched OpenSSH. This experiment has now been running for just over two weeks, and there are some interesting results. I’ve been tweeting these since the start.

As expected, the vast majority of password-guessing attempts are quite dull, and fall into one of two categories. Firstly there are attempts with a large number of ‘poor’ passwords (e.g. “password”, “1234″, etc…) against a small number of accounts which are very likely to exist (almost always “root”, but sometimes others such as “bin”).

Secondly, there were attempts on a large number of accounts which might plausibly exist (e.g. common first names and software packages such as ‘oracle’). For these, there were a very small number of password attempts, normally only trying the username as password. Well established good practices such as choosing a reasonably strong password and denying password-based log-in to the root account will be effective against both categories of attacks. Surprisingly, there were few attempts which were obviously default passwords from software packages (but they perhaps were hidden in the attempts where username equalled password). However, one attempt was username: “rfmngr”, password: “$rfmngr$”, which is the default password for Websense RiskFilter (see p.10 of the manual).

There were, however, some more interesting attempts. (more…)

May 9, '11

About a moth ago I’ve presented at the Security Protocols Workshop a new idea to detect relay attacks, co-developed with Frank Stajano.

The idea relies on having a trusted box (which we call the T-Box as in the image below) between the physical interfaces of two communicating parties. The T-Box accepts 2 inputs (one from each party) and provides one output (seen by both parties). It ensures that none of the parties can determine the complete input of the other party.

T-Box

Therefore by connecting 2 instances of a T-Box together (as in the case of a relay attack) the message from one end to the other (Alice and Bob in the image above) gets distorted twice as much as it would in the case of a direct connection. That’s the basic idea.

One important question is how does the T-Box operate on the inputs such that we can detect a relay attack? In the paper we describe two example implementations based on a bi-directional channel (which is used for example between a smart card and a terminal). In order to help the reader understand these examples better and determine the usefulness of our idea Mike Bond and I have created a python simulation. This simulation allows you to choose the type of T-Box implementation, a direct or relay connection, as well as other parameters including the length of the anti-relay data stream and detection threshold.

In these two implementations we have restricted ourselves to make the T-Box part of the communication channel. The advantage is that we don’t rely on any party providing the T-Box since it is created automatically by communicating over the physical channel. The disadvantage is that a more powerful attacker can sample the line at twice the speed and overcome our T-Box solution.

The relay attack can be used against many applications, including all smart card based payments. There are already several ideas, including distance bounding, for detecting relay attacks. However our idea brings a new approach to the existing methods, and we hope that in the future we can find a practical implementation of our solutions, or a good scenario to use a physical T-Box which should not be affected by a powerful attacker.

Mar 27, '11

Passwords are no longer acceptable as a security mechanism. The arrogant security people ask users that passwords be memorable, unguessable, high entropy, all different and never written down. With the proliferation of the number of passwords and the ever-increasing brute-force capabilities of modern computers, passwords of adequate strength are too complicated for human memory, especially when one must remember dozens of them. The above demands cannot all be satisfied simultaneously. Users are right to be pissed off.

A number of proposals have attempted to find better alternatives for the case of web authentication, partly because the web is the foremost culprit in the proliferation of passwords and partly because its clean interfaces make technical solutions tractable.

For the poor user, however, a password is a password, and it’s still a pain in the neck regardless of where it comes from. Users aren’t fed up with web passwords but with passwords altogether. In “Pico: no more passwords, the position paper I’ll be presenting tomorrow morning at the Security Protocols Workshop, I propose a clean-slate design to get rid of passwords everywhere, not just online. A portable gadget called Pico transforms your credentials from “what you know” into “what you have”.

A few people have already provided interesting feedback on the pre-proceedings draft version of the paper. I look forward to an animated discussion of this controversial proposal tomorrow. Whenever I serve as help desk for my non-geek acquaintances and listen to what drives them crazy about computers I feel ashamed that, with passwords, we (the security people) impose on them such a contradictory and unsatisfiable set of requests. Maybe your gut reaction to Pico will be “it’ll never work”, but I believe we have a duty to come up with something more usable than passwords.

[UPDATE: the paper can also be downloaded from my own Cambridge web site, where the final version will appear in due course.]

Mar 24, '11

My paper Can We Fix the Security Economics of Federated Authentication? asks how we can deal with a world in which your mobile phone contains your credit cards, your driving license and even your car key. What happens when it gets stolen or infected?

Using one service to authenticate the users of another is an old dream but a terrible tar-pit. Recently it has become a game of pass-the-parcel: your newspaper authenticates you via your social networking site, which wants you to recover lost passwords by email, while your email provider wants to use your mobile phone and your phone company depends on your email account. The certification authorities on which online trust relies are open to coercion by governments – which would like us to use ID cards but are hopeless at making systems work. No-one even wants to answer the phone to help out a customer in distress. But as we move to a world of mobile wallets, in which your phone contains your credit cards and even your driving license, we’ll need a sound foundation that’s resilient to fraud and error, and usable by everyone. Where might this foundation be? I argue that there could be a quite surprising answer.

The paper describes some work I did on sabbatical at Google and will appear next week at the Security Protocols Workshop.

Oct 19, '10

During my MPhil within the Computer Lab (supervised by Markus Kuhn) I developed a card-sized device (named Smart Card Detective – in short SCD) that can monitor Chip and PIN transactions. The main goal of the SCD was to offer a trusted display for anyone using credit cards, to avoid scams such as tampered terminals which show an amount on their screen but debit the card another (see this paper by Saar Drimer and Steven Murdoch). However, the final result is a more general device, which can be used to analyse and modify any part of an EMV (protocol used by Chip and PIN cards) transaction.

Using the SCD we have successfully shown how the relay attack can be mitigated by showing the real amount on the trusted display. Even more, we have tested the No PIN vulnerability (see the paper by Murdoch et al.) with the SCD. A reportage on this has been shown on Canal+ (video now available here).

After the “Chip and PIN is broken” paper was published some contra arguments referred to the difficulty of setting up the attack. The SCD can also show that such assumptions are many times incorrect.

More details on the SCD are on my MPhil thesis available here. Also important, the software is open source and along with the hardware schematics can be found in the project’s page. The aim of this is to make the SCD a useful tool for EMV research, so that other problems can be found and fixed.

Thanks to Saar Drimer, Mike Bond, Steven Murdoch and Sergei Skorobogatov for the help in this project. Also thanks to Frank Stajano and Ross Anderson for suggestions on the project.

Jul 30, '10

This is the fourth and final part in a series on password implementations at real websites, based on my paper at WEIS 2010 with Sören Preibusch.

Given the problems associated with passwords on the web outlined in the past few days, for years academics have searched for new technology to replace passwords. This thinking can at times be counter-productive, as no silver bullets have yet materialised and this has distracted attention away from fixing the most pressing problems associated with passwords. Currently, the trendiest proposed solution is to use federated identity protocols to greatly reduce the number of websites which must collect passwords (as we’ve argued would be a very positive step). Much focus has been given to OpenID, yet it is still struggling to gain widespread adoption. OpenID was deployed at less than 3% of websites we observed, with only Mixx and LiveJournal giving it much prominence.

Nevertheless, we optimistically feel that real changes will happen in the next few years, as password authentication on the web seems to be becoming increasingly unsustainable due to the increasing scale and interconnectivity of websites collecting passwords. We actually think we are already in the early stages of a password revolution, just not of the type predicted by academia.

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Jul 27, '10

Sören Preibusch and I have finalised our in-depth report on password practices in the wild, The password thicket: technical and market failures in human authentication on the web, presented in Boston last month for WEIS 2010. The motivation for our report was a lack of technical research into real password deployments. Passwords have been studied as an authentication mechanism quite intensively for the last 30 years, but we believe ours was the first large study into how Internet sites actually implement them. We studied 150 sites, including the most visited overall sites plus a random sample of mid-level sites. We signed up for free accounts with each site, and using a mixture of scripting and patience, captured all visible aspects of password deployment, from enrolment and login to reset and attacks.

Our data (which is now publicly available) gives us an interesting picture into the current state of password deployment. Because the dataset is huge and the paper is quite lengthy, we’ll be discussing our findings and their implications from a series of different perspectives. Today, we’ll focus on the preventable mistakes. In academic literature, it’s assumed that passwords will be encrypted during transmission, hashed before storage, and attempts to guess usernames or passwords will be throttled. None of these is widely true in practice.

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Jul 26, '10

We have a new paper on the strategic vulnerability created by the plan to replace Britain’s 47 million meters with smart meters that can be turned off remotely. The energy companies are demanding this facility so that customers who don’t pay their bills can be switched to prepayment tariffs without the hassle of getting court orders against them. If the Government buys this argument – and I’m not convinced it should – then the off switch had better be closely guarded. You don’t want the nation’s enemies to be able to turn off the lights remotely, and eliminating that risk could just conceivably be a little bit more complicated than you might at first think. (This paper follows on from our earlier paper On the security economics of electricity metering at WEIS 2010.)

May 18, '10

Steven Murdoch, Saar Drimer, Mike Bond and I have just won the IEEE Security and Privacy Symposium’s Best Practical Paper award for our paper Chip and PIN is Broken. This was an unexpected pleasure, given the very strong competition this year (especially from this paper). We won this award once before, in 2008, for a paper on a similar topic.

Ross, Mike, Saar, Steven (photo by Joseph Bonneau)

Update (2010-05-28): The photo now includes the full team (original version)


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