Category Archives: Authentication


Last week I gave a keynote talk at CCS about DigiTally, a project we’ve been working on to extend mobile payments to areas where the network is intermittent, congested or non-existent.

The Bill and Melinda Gates Foundation called for ways to increase the use of mobile payments, which have been transformative in many less developed countries. We did some research and found that network availability and cost were the two main problems. So how could we do phone payments where there’s no network, with a marginal cost of zero? If people had smartphones you could use some combination of NFC, bluetooth and local wifi, but most of the rural poor in Africa and Asia use simple phones without any extra communications modalities, other than those which the users themselves can provide. So how could you enable people to do phone payments by simple user actions? We were inspired by the prepayment electricity meters I helped develop some twenty years ago; meters conforming to this spec are now used in over 100 countries.

We got a small grant from the Gates Foundation to do a prototype and field trial. We designed a system, Digitally, where Alice can pay Bob by exchanging eight-digit MACs that are generated, and verified, by the SIM cards in their phones. For rapid prototyping we used overlay SIMs (which are already being used in a different phone payment system in Africa). The cryptography is described in a paper we gave at the Security Protocols Workshop this spring.

Last month we took the prototype to Strathmore University in Nairobi to do a field trial involving usability studies in their bookshop, coffee shop and cafeteria. The results were very encouraging and I described them in my talk at CCS (slides). There will be a paper on this study in due course. We’re now looking for partners to do deployment at scale, whether in phone payments or in other apps that need to support value transfer in delay-tolerant networks.

There has been press coverage in the New Scientist, Engadget and Impress (original Japanese version).

GCHQ helps banks dump fraud losses on customers

We recently reported that the Commissioner of the Met, Sir Bernard Hogan-Howe, said that banks should not refund fraud victims as this would just make people careless with their passwords and antivirus. The banks’ desire to blame fraud victims if they can, to avoid refunding them, is rational enough, but for a police chief to support them was disgraceful. Thirty years ago, a chief constable might have said that rape victims had themselves to blame for wearing nice clothes; if he were to say that nowadays, he’d be sacked. Hogan-Howe’s view of bank fraud is just as uninformed, and just as offensive to victims.

Our spooky friends at Cheltenham have joined the party. The Register reports a story in the Financial Times (behind a paywall) which says GCHQ believes that “companies must do more to try and encourage their customers to improve their cyber security standards. Customers using outdated software – sometimes riddled with vulnerabilities that hackers can exploit – are a weak link in the UK’s cyber defences.” There is no mention of the banks’ own outdated technology, or of GCHQ’s role in keeping consumer software vulnerable.

The elegant scribblers at the Financial Times are under the impression that “At present, banks routinely cover the cost of fraud, regardless of blame.” So they clearly are not regular readers of Light Blue Touchpaper.

The spooks are slightly more cautious; according to the FT, GCHQ “has told the private sector it will not take responsibility for regulatory failings”. I’m sure the banks will heave a big sigh of relief that their cosy relationship with the police, the ombudsman and the FCA will not be disturbed.

We will have to change our security-economics teaching material so we don’t just talk about the case where “Alice guards a system and Bob pays the costs of failure”, but also this new case where “Alice guards a system, and bribes the government to compel Bob to pay the costs of failure.” Now we know how Hogan-Howe is paid off; the banks pay for his Dedicated Card and Payment Crime Unit. But how are they paying off GCHQ, and what else are they getting as part of the deal?

Security Protocols 2016

I’m at the 24th security protocols workshop in Brno (no, not Borneo, as a friend misheard it, but in the Czech republic; a two-hour flight rather than a twenty-hour one). We ended up being bumped to an old chapel in the Mendel museum, a former monastery where the monk Gregor Mendel figured out genetics from the study of peas, and for the prosaic reason that the Canadian ambassador pre-empted our meeting room. As a result we had no wifi and I have had to liveblog from the pub, where we are having lunch. The session liveblogs will be in followups to this post, in the usual style.

My Yahoo! password histograms are now available (with differential privacy!)

5 years ago, I compiled a dataset of password histograms representing roughly 70 million Yahoo! users. It was the largest password dataset ever compiled for research purposes. The data was a key component of my PhD dissertation the next year and motivated new statistical methods for which I received the 2013 NSA Cybersecurity Award.

I had always hoped to share the data publicly. It consists only of password histograms, not passwords themselves, so it seemed reasonably safe to publish. But without a formal privacy model, Yahoo! didn’t agree. Given the history of deanonymization work, caution is certainly in order. Today, thanks to new differential privacy methods described in a paper published at NDSS 2016 with colleagues Jeremiah Blocki and Anupam Datta, a sanitized version of the data is publicly available.

Continue reading My Yahoo! password histograms are now available (with differential privacy!)

Can we crowdsource trust?

Your browser contains a few hundred root certificates. Many of them were put there by governments; two (Verisign and Comodo) are there because so many merchants trust them that they’ve become ‘too big to fail’. This is a bit like where people buy the platform with the most software – a pattern of behaviour that let IBM and then Microsoft dominate our industry in turn. But this is not how trust should work; it leads to many failures, some of them invisible.

What’s missing is a mechanism where trust derives from users, rather than from vendors, merchants or states. After all, the power of a religion stems from the people who believe in it, not from the government. Entities with godlike powers that are foisted on us by others and can work silently against us are not gods, but demons. What can we do to exorcise them?

Do You Believe in Tinker Bell? The Social Externalities of Trust explores how we can crowdsource trust. Tor bridges help censorship victims access the Internet freely, and there are not enough of them. We want to motivate lots of people to provide them, and the best providers are simply those who help the most victims. So trust should flow from the support of the users, and it should be hard for powerful third parties to pervert. Perhaps a useful mascot is Tinker Bell, the fairy in Peter Pan, whose power waxes and wanes with the number of children who believe in her.

Double bill: Password Hashing Competition + KeyboardPrivacy

Two interesting items from Per Thorsheim, founder of the PasswordsCon conference that we’re hosting here in Cambridge this December (you still have one month to submit papers, BTW).

First, the Password Hashing Competition “have selected Argon2 as a basis for the final PHC winner”, which will be “finalized by end of Q3 2015”. This is about selecting a new password hashing scheme to improve on the state of the art and make brute force password cracking harder. Hopefully we’ll have some good presentations about this topic at the conference.

Second, and unrelated: Per Thorsheim and Paul Moore have launched a privacy-protecting Chrome plugin called Keyboard Privacy to guard your anonymity against websites that look at keystroke dynamics to identify users. So, you might go through Tor, but the site recognizes you by your typing pattern and builds a typing profile that “can be used to identify you at other sites you’re using, were identifiable information is available about you”. Their plugin intercepts your keystrokes, batches them up and delivers them to the website at a constant pace, interfering with the site’s ability to build a profile that identifies you.

Passwords 2015 call for papers

The  9th International Conference on Passwords will be held at Cambridge, UK on 7-9 December 2015.

Launched in 2010 by Per Thorsheim,  Passwordscon is a lively and entertaining conference series dedicated solely to passwords. Passwordscon’s unique mix of refereed papers and hacker talks encourages a kind of cross-fertilization that I’m sure you’ll find both entertaining and fruitful.

Paper submissions are due by 7 September 2015. Selected papers will be included in the event proceedings, published by Springer in the Lecture Notes in Computer Science (LNCS) series.

We hope to see lots of you there!

Graeme Jenkinson, Local arrangements chair

Security Protocols 2015

I’m at the 23rd Security Protocols Workshop, whose theme this year is is information security in fiction and in fact. Engineering is often inspired by fiction, and vice versa; what might we learn from this?

I will try to liveblog the talks in followups to this post.