Usable Security Systems, a CommerceNet portfolio company founded by Rachna Dhamija and Allan M. Schiffman, is launching its product, UsableLogin, at DEMOfall08 in San Diego today.
If you’re at DEMO, make sure to tell the Usable team that we’re proud of them!
We are offering a couple internship positions at CommerceNet this summer.
CommerceNet is an entrepreneurial research institute, dedicated to fulfill the promise of the Internet. We are currently seeking Software Engineer interns to implement a data visualization Web application for public health information. Involves JavaScript and Python, both data access and graphics. CommerceNet may also accept proposals for internships to work on well-specified projects of the intern’s own design.
What you’ll do
Required Skills:
Email cn-hr@commerce.net with questions or cover letter and resume.
A goal of many new Web “2.0″ ventures is to build a large or at least persistent community. Success is difficult to measure, but breaking into the top 100,000 sites by traffic measured by Alexa is one goal. It might be a good sign if the site designers send emails to a few people asking them to take a look at the site and after only two days over 3000 people sign up to beta test. You could do worse than to have a list of 60,000 people desperate to join your site before it leaves beta — so desperate that the site admins put a “waiting list checker” page up just so that an impatient person can see how many people are in line to get accounts before he or she does. Read the rest of this entry »
The 69th IETF was last week in Chicago (windy and good pizza, who knew?). The two highlights for me were the HTTP Bis BoF and the BIFF BoF. A BoF is a “Birds of a Feather” meeting used to gauge interest and feasibility towards forming an IETF working group.
A new authentication scheme was announced recently at the Web 2.0 Expo: Vidoop http://www.vidoop.com.
Vidoop describes itself as a web single sign-on solution that is resistant to “all prevalent forms of hacking”. Specifically, they claim to resist “phishing, keystroke logging, brute force, and many man-in-the-middle attacks” and to resist automated attacks by “requiring human cognition” on the part of the attacker. This language is misleading. In reality, the scheme only resists simple phishing attacks — it does not prevent man-in-the-middle attacks, is vulnerable to brute force attacks, and it is resistant to keyboard loggers only when screen loggers are not present.
We were able to construct a man-in-the-middle (MITM) attack that allows us to capture users’ credentials and to login to their accounts. We recorded a video that demonstrates a MITM attack in progress at myvidoop.com. Ian Fischer, a Harvard University student and research intern at CommerceNet, created the attack in a few hours, by modifying freely available proxy software on the Internet. We describe the attacks in more detail below.
How Vidoop works: Vidoop is essentially a combination of a graphical password scheme and client-side cookie. During setup, a user must choose their secret, which is a set of three “image categories” out of 25 categories (e.g., the user might choose cats, dogs, and birds).
To login, the user has to enter their username (or OpenID URI). The server presents a grid of 12 images from different image categories. Each picture has a random character superimposed on it, and three of the images are from the user’s pre-selected categories. The user derives his one-time PIN by entering the three letters corresponding to his image categories.
Attacks: We recently conducted a study that analyzed attacks on Bank of America’s SiteKey scheme [1]. Vidoop bears some similarities and shares many of the same vulnerabilities. In particular, Vidoop is vulnerable to a man-in-the-middle attack in which the attacker simulates the enrollment process. This is a well-know attack on SiteKey, which was first published in 2005 [2], and has been well analyzed by Jim Youll [3] and more recently demonstrated in this video by Indiana University researchers [4].
Like SiteKey, users must have a Flash cookie and/or HTTP cookie on their machine in order to log in (this cookie acts as a “second factor” that ties the machine to the user’s account). If this cookie is erased, or if the user logs in from a new machine, the user needs to “enroll” the machine. The SiteKey enrollment process requires the user to answer a challenge question before receiving their cookie. This opens up a MITM attack, where the phisher lures the user to his website and presents the enrollment message “You are logging in from a computer that we don’t recognize”. The phisher proceeds to relay the challenge question from the bank to the user, and then relays the user’s answer back to the bank. This allows the phisher to ultimately capture the user’s SiteKey image and password. Because the user has probably seen the re-enrollment message several times in legitimate circumstances, he is likely to answer the challenge question and might not even know he was the victim of a phishing attack.
In Vidoop’s enrollment process, the user has to request an activation code, instead of answering a challenge question (the activation code is delivered via email, a phone call or SMS text message). Once the user enters the activation code, the server will place a cookie on the machine, and allow the user to log in as usual. This opens up the same MITM described above — now, instead of relaying the challenge question to the bank, the phisher simply relays the activation code:
The phisher directs the user to phishingsite.com, which looks just like the Bank site, and the user enters his username.
The phisher relays the username to the real Bank and is presented with the message “We don’t recognize your computer. Please select how you would like to receive your activation code”. The phisher relays this message to the user.
The user selects the method of delivery, and the phisher relays this choice to the Bank. The user receives the activation code and enters it into the phishing website.
The phisher relays the activation code to the Bank, receives the cookie, and the user’s authentication grid image.
The phisher displays the user’s image grid to the user in order to obtain his PIN and secret “image categories”. He relays the PIN back to the bank in order to log in.
Vidoop’s requirement for out-of-band communication does not increase the cost of launching an automated MITM attack. In the SiteKey attack, the MITM phisher obtains the SiteKey image and password and a secure cookie, which allows him to log in indefinitely. In Vidoop, the MITM attacker obtains the user’s PIN, which can only be used immediately to login to the account one time. He also receives the user’s image categories and a cookie that allows him to log in in the future. To make use of the cookie, the attacker has to do a little more work.
Vidoop claims that subsequent logins require a human to determine the image categories and to look at the image grid to obtain the user’s PIN. The necessity for a human in the loop increases the cost of an attack, and most phishers won’t bother to go through the effort. They don’t need to! The password space is so small that, once you have a cookie, a brute force attack is trivial. The myvidoop.com PIN is 3 characters chosen from the 26 characters of the alphabet, is order-independent, and is case insensitive, so the attacker only has to search 2,600 combinations (26 choose 3). With four login attempts available, the chances of success are 1 in 650. If the phisher uses automated character-recognition programs, he can reduce the number of combinations to 220 (12 choose 3), or a 1 in 55 chance of success with 4 login attempts. Note that brute force attacks are also easy to mount by anyone that shares the machine with the user.
Vidoop could increase the attacker workload by increasing the size of the PIN (the number of image categories), increasing the image grid, increasing character set (e.g., adding digits and symbols), requiring order dependence and non-repeatability, or by reducing the number of attempts that are allowed. To defeat character recognition, they could eventually employ captcha-type characters. All of these options will significantly reduce the usability of the system.
Vidoop does improve upon SiteKey in its resistance to keyboard logging attacks. If a keyboard logger obtains the PIN, it is only useful for one login and only within the timeout period. Vidoop is not resistant to malware that contains both keyboard loggers and screen loggers, which are becoming increasingly common [5].
Graphical passwords do have other weaknesses. For example, an attacker can predict the type of image categories that are chosen, even with very limited information about the target user [6, 7]. However, targeted attacks are expensive to mount — we’ve only focused on the attacks that are easy to automate here.
Privacy: There is a gaping privacy hole in their system. Vidoop makes it easy to search for registered usernames, and they openly publish these on their website. An attacker can enter usernames and request that activation codes be sent to them via text message, cell phone or email, depending on the user’s preferences (this can be very costly and annoying for both Vidoop and its users). Initially, Vidoop had no time-out or restriction on the number of messages that could be sent by an unknown party. It appears that I can now only send 3 messages to any one person, after which time there is 9 minute timeout before requests can be sent again. By signing up for Vidoop, users essentially give anyone the right to send them Vidoop messages, without requesting their permission and without needing any contact information.
Usability: The cognitive overhead of selecting the Vidoop PIN is higher than recognizing the previously seen SiteKey image (the user must remember their semantic image categories, select images from the appropriate categories, find the associated characters and input them into a text box). However, Vidoop eliminates the need to recall a password, which is still a requirement with SiteKey. Vidoop eliminates the need to answer a challenge question during enrollment, but requires the user to check their email or phone and then input the activation code.
Summary: Before publishing our analysis, we communicated with Vidoop’s CTO, Scott Blomquist. He acknowledged that he is aware of these weaknesses and that the scheme is vulnerable to man-in-the-middle attacks. In comparison to simple password authentication, Vidoop does raise the bar for phishers. However, we find their advertising, and in particular their claims that they resist man-in-the-middle attacks and “all prevalent forms of hacking”, to be disingenuous.
[1] The Emperor’s New Security Indicators, Stuart Schecter, Rachna Dhamija, Andy Ozment, Ian Fischer, to appear in the Proceedings IEEE Symposium on Security and Privacy, May 2007.
[2] The Battle Against Phishing: Dynamic Security Skins, Rachna Dhamija and J. D. Tygar, in Proceedings of the Symposium on Usable Privacy and Security (SOUPS), July 2005.
[3] Fraud Vulnerabilities in SiteKey Security at Bank of America, Jim Youll, July 2006.
[4] Deciet Augmented Man-in-the-middle Attack against Bank of America SiteKey Service, blog post and video, Christopher Soghoian, April 10, 2007.
[5] Anti-phishing Working Group, http://www.apwg.org/
[6] Deja Vu: A User Study. Using Images for Authentication, Rachna Dhamija and Adrian Perrig, in Proceedings of the 9th USENIX Security Symposium, August 2000.
[7] On User Choice in Graphical Password Schemes, Darren Davis, Fabian Monrose, and Michael K. Reiter, in Proceedings of the 13th USENIX Security Symposium, August 2004.
A longer, though not necessarily more accurate job description, can be found here.
I’ve been told in the past that Open Source and Open Standards are practically the same thing, they go so well together. While they’re both good things, unfortunately, they’re not quite as naturally reinforcing as you’d like. There’s cost and style of participation, IPR concerns, and proliferation of standards (”The good thing about standards is, there’s so many to choose from” — ref).
A month ago at the last IETF meeting, I talked to a bunch of email standards experts about the current wave of Internet email standards work. In these conversations I also built a mental picture of the previous waves.
Wave 1 was what really made email work over the Internet. The Simple Mail Transfer Protocol and the basic email message format were defined in 1982 with the major innovation of using domain names to find out where to deliver an email. This allowed email from one organization to reach an individual in another company. In 1989, this was somewhat updated with RFC1123, which made email addresses look the way they do today: mailbox@domain.example. Once mail got to the right server, POP (first described in RFC918 in 1984) allowed any mail client to look through the server’s queue of new mail and decide what to do with each message. Although that first POP was described so early, many did not use it in those years and it didn’t get much attention until POP3. Instead one would typically log into the SMTP server and look at its mailboxes there.
Wave 2 was POP3, IMAP and MIME, 1988 to 1994 or so. POP3 gained far more adoption than POP. IMAP defined a way to access the server-side repository for all one’s mail: not just the queue of new messages, but a hierarchy of mailboxes (called “folders” in many clients) which can be used to store mail for access by several clients. MIME brought Media to electronic mail: the ability to include image file formats, to use HTML instead of text, to attach Word documents and executables, and other variations necessary to business and eventually much beloved by spammers. MIME also introduced the very first non-ASCII characters in the body of email. MIME turned out to be big for other purposes too, like the Web.
There’s arguably a wave 2.5 or 3, adding security features from 1994 to 1999, including S/MIME, TLS support and authentication features for IMAP and SMTP. SASL was added to SMTP in 1999 although didn’t get put into IMAP until 2003. This mini-wave didn’t change peoples’ lives much except for those whose companies rolled out complicated and hard-to-use S/MIME infrastructures, but the continued deployment of IMAP and MIME over this period did change the email habits of many.
Today’s wave is starting to get complicated (oh, just starting? heh). It’s adding internationalization capability, step by painful step (to various IMAP functions, to various mail headers like an email Subject line, and most painfully, to email addresses themselves). It’s making IMAP and other mail infrastructure more usable by mobile clients (all the work of the Lemonade WG). It’s addressing security and spam, among other things new ways to sign messages (DKIM). There is also some refactoring and architectural work going on which may be very interesting in the long run — for example, features to assign URLs and attach metadata to IMAP messages. This kind of work already allows increasing innovation in how email clients can deal with mail (particularly mail overload and spam).
The people I work with today include:
Of course, although talking to some of these guys helped me put together this picture of email standardization waves, any errors here are mine (and please let me know of errors so I can update this).
I’ve been seeing the word “compliance” tossed around a lot for HTTP and other standards lately, with much ambiguity. Let’s say you read RFC2068 and implemented a client very carefully. Does it make your client implementation “uncompliant” if a new standard updates or obsoletes RFC2068 and adds requirements, as RFC2616 did?
My answer is “that’s not even a meaningful question”. Compliance can be a very loose concept.
With this knowledge, you can ask if the new caching features in RFC2616 made existing clients uncompliant with RFC2068. Of course not. RFC2068 didn’t change — there’s a reason the IETF doesn’t replace its standards in-place but defines new RFC numbers. Do the new caching features make the client uncompliant with RFC2616? Well it never claimed to be compliant with a spec that was probably published after the client was written. The important question to ask is whether a new feature or requirement is backwards-compatible (and if it’s not, whether the feature is important enough to break backwards-compatibility). Let’s consider The Cache-Control header a little further: a response with “Cache-Control: no-store” can be sent to any client that advertised HTTP/1.1 support, because that directive works the same way in both specs. If the response has “Cache-Control: s-maxage=1600″, then we’re not so sure if all HTTP/1.1 clients support it, but that might be OK — only shared caches can possibly do the wrong thing if they don’t implement RFC2616 yet, and the server could limit the out-of-date cache entries of pre-2616 shared caches by having a backup plan, e.g. “Cache-Control: s-maxage=1600, maxage=36000″.
This new feature was a reasonable choice in the standardization of RFC2616. If the writers of RFC2616 had been prevented from making any requirements that weren’t already met in deployed clients, they would not have been able to add features like “maximum age limits for shared cache entries”. The limitation would have unduly restricted their ability to improve RFC2616. Instead, the authors considered whether each feature was worth the new code and other design/test effort, and the backwards-compatibility considerations, and whether there were reasonable work-arounds or fall-backs.
It’s a very engineering approach but that’s what we do at the IETF. We don’t do scientific theories of protocol compliance that must be true for all instances of protocol X. We do engineering.
I signed up to do a talk called “Beyond Passwords” at ApacheCon US 2006, which took place in Austin last week. I had originally intended to talk rather blandly about current standards efforts. But in the end I took a much more contrarian approach and examined the promises of Identity 2.0, how policies and implementation progress are likely to affect the real benefits, and the risks or threats. It is a skeptical guide to a potential relying party — a Web service that is considering relying on some 3rd-party to authenticate and identify its users — on how to evaluate the benefits and the costs. Read the rest of this entry »
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