Archive for 2008

Students get crash course in sciences at UVa camp

Sunday, July 20th, 2008

The Charlottesville Daily Progress has an article by John Henderson about the Bernard Harris Summer Science Camp at UVa: <a href=””><em>Students get crash course in science at UVa camp</em></a>, The Daily Progress, 18 July 2008.  It describes some lessons we did on cryptography.  The handouts we used for this are here: <a href=””><em></em></a>.

NXP Lawsuit

Thursday, July 10th, 2008

NXP is suing Radboud University in the Netherlands to prevent them publishing a paper (in ESORICS 2008 in October) containing details on the Mifare classic encryption algorithm (and various flaws they have found in the algorithm). Perhaps the title of the paper, “Dismantling MIFARE Classic”, got NXP’s attention. A hearing is scheduled for July 10.


[Update 18 July] The judge has denied NXP’s request for an injunction, ruling that “limitations to the freedom of speech are allowed only if there is urgent and obvious threat to society”: Judge denies NXP’s injunction against security researchers, Industry Standard, 18 July 2008.

[Update 21 July] Another article: Dutch court allows publication of Mifare security hole research, CNet News, 18 July 2008. This one includes a picture of Karsten Nohl’s presentation at the Last HOPE Conference.

Credit Cards Stolen Without Leaving Wallet

Friday, June 20th, 2008

KIRO TV (Seattle) has a story on RFID privacy issues: Credit Cards Stolen Without Leaving Wallet (it includes a video demonstration).

German-born Karsten Nohl is a security consultant and PhD student at the University of Virginia. He was in Seattle recently to speak at a technology conference and is known worldwide for hacking into transit systems.

He’s exposed significant security problems with transit cards commuters were told held their personal information secure, but Nohl showed, did not

“Is it all that inconvenient to swipe a card? Does it really have to be tapping? Would, for that perhaps tiny added benefit, now expose your data to everybody in your vicinity? Perhaps not. So, that is a discussion that has to be had. And not just by the companies introducing something new and fancy and forcing everybody to use it, but rather by the consumers, too,” said Nohl.

More news about Adrienne Felt’s Facebook Privacy Work

Saturday, June 14th, 2008

Kim Hart has written an article covering Adrienne Felt’s study of privacy issues with Facebook applications: A Flashy Facebook Page, at a Cost to Privacy: Add-Ons to Online Social Profiles Expose Personal Data to Strangers, The Washington Post, 12 June 2008.

Ben Ling, director of Facebook’s platform, said that developers are not allowed to share data with advertisers but that they can use it to tailor features to users. Facebook now removes applications that abuse user data by, for example, forcing members to invite all of their friends before they can use it.

“When we find out people have violated that policy, there is swift enforcement,” he said.

But it is often difficult to tell when developers are breaking the rules by, for example, storing members’ data for more than 24 hours, said Adrienne Felt, who recently studied Facebook security at the University of Virginia.

She examined 150 of the most popular Facebook applications to find out how much data could be gathered. Her research, which was presented at a privacy conference last month, found that about 90 percent of the applications have unnecessary access to private data.

“Once the information is on a third-party server, Facebook can’t do anything about it,” she said. Developers can use it to provide targeted ads based on a member’s gender, age or relationship status.

The article also appeared in MSNBC, the Kansas City Star, the Los Angeles Times (Facebook widgets pose privacy risks:Users often give away their personal data and that of friends without knowing when they install the popular social network programs), the Austin American-Statesman (Social networking applications could become a privacy headache), and the Washington Post’s Express edition (FreeRide Lunchtime Reading: Who’s Getting in Your Facebook?).


Interview on Program Analysis Tools

Monday, June 2nd, 2008

Electronic Design has an interview with me: Electronic Design Interviews U. of Virginia Computer Prof, Electronic Design, 21 May 2008. The interview focuses on the history of Splint, and the current state and future of program analysis tools.

Facebook Vulnerable To Serious XSS Attack

Saturday, May 31st, 2008

Another XSS vulnerability has been discovered in Facebook, as reported by InformationWeek (George Hulme). The posting also links to Adrienne Felt’s Facebook security work.

Reverse-Engineering a Cryptographic RFID Tag

Wednesday, May 14th, 2008

Our upcoming USENIX Security Symposium paper is now available: Reverse-Engineering a Cryptographic RFID Tag by Karsten Nohl, David Evans, Starbug, and Henryk Plötz.

The paper describes the methods used to reverse engineering the encryption on the Mifare Classic RFID tag and some of the things we learned by doing it. Karsten Nohl will present the paper at the USENIX Security Symposium in San Jose on July 31.


The security of embedded devices often relies on the secrecy of proprietary cryptographic algorithms. These algorithms and their weaknesses are frequently disclosed through reverse-engineering software, but it is commonly thought to be too expensive to reconstruct designs from a hardware implementation alone. This paper challenges that belief by presenting an approach to reverse-engineering a cipher from a silicon implementation. Using this mostly automated approach, we reveal a cipher from an RFID tag that is not known to have a software or micro-code implementation. We reconstruct the cipher from the widely used Mifare Classic RFID tag by using a combination of image analysis of circuits and protocol analysis. Our analysis reveals that the security of the tag is even below the level that its 48-bit key length suggests due to a number of design flaws. Weak random numbers and a weakness in the authentication protocol allow for pre-computed rainbow tables to be used to find any key in a matter of seconds. Our approach of deducing functionality from circuit images is mostly automated, hence it is also feasible for large chips. The assumption that algorithms can be kept secret should therefore to be avoided for any type of silicon chip.

Full paper (9 pages): [PDF] [HTML]

Congratulations Dr. Paul!

Tuesday, May 13th, 2008

Nathanael Paul’s PhD dissertation has been approved! He will graduate this Sunday.

The dissertation is available here: Disk-Level Malware Detection [Abstract] [Full text: PDF, 155 pages].

Congratulations, Nate! (That is, “Dr. Paul”.) Nate is currently a post-doctoral fellow at Vrije Universiteit, Amsterdam working with Andrew Tanenbaum.

Privacy Protection for Social Networking Platforms

Monday, May 5th, 2008

Our paper, Privacy Protection for Social Networking Platforms by Adrienne Felt and David Evans is now available [PDF]. Adrienne Felt will present the paper at the Web 2.0 Security and Privacy 2008 (in conjunction with 2008 IEEE Symposium on Security and Privacy) in Oakland, CA on May 22, 2008.


Social networking platforms integrate third-party content into social networking sites and give third-party developers access to user data. These open interfaces enable popular site enhancements but pose serious privacy risks by exposing user data to third-party developers. We address the privacy risks associated with social networking APIs by presenting a privacy-by-proxy design for a privacy-preserving API. Our design is motivated by an analysis of the data needs and uses of Facebook applications. We studied 150 popular Facebook applications and found that nearly all applications could maintain their functionality using a limited interface that only provides access to an anonymized social graph and placeholders for user data. Since the platform host can control the third party applications’ output, privacy-by-proxy can be accomplished by using new tags and data transformations without major changes to either the platform architecture or applications.

Full paper (8 pages): [PDF]
Project Website

[Added 25 May]: Talk slides (by Adrienne Felt): [PDF]

Hiding in Groups

Monday, April 28th, 2008

Our paper, Hiding in Groups: On the Expressiveness of Privacy Distributions by Karsten Nohl and David Evans, is now available: PDF (15 pages). Karsten Nohl will present the paper at the 23rd International Information Security Conference (SEC 2008, Co-located with IFIP World Computer Congress 2008) in Milan, Italy, 8-10 September 2008.


Many applications inherently disclose information because perfect privacy protection is prohibitively expensive. RFID tags, for example, cannot be equipped with the cryptographic primitives needed to completely shield their information from unauthorized reads. All known privacy protocols that scale to the anticipated sizes of RFID systems achieve at most modest levels of protection. Previous analyses found the protocols to have weak privacy, but relied on simplifying attacker models and did not provide insights into how to improve privacy. We introduce a new general way to model privacy through probability distributions, that capture how much information is leaked by different users of a system. We use this metric to examine information leakage for an RFID tag from the a scalable privacy protocol and from a timing side channel that is observable through the tag’s random number generator. To increase the privacy of the protocol, we combine our results with a new model for rational attackers to derive the overall value of an attack. This attacker model is also based on distributions and integrates seamlessly into our framework for information leakage. Our analysis points to a new parameterization for the privacy protocol that significantly improves privacy by decreasing the expected attack value while maintaining reasonable scalability at acceptable cost.

Full paper (15 pages): [PDF]

Extended Technical Report (18 pages): [PDF]