Alexei Czeskis

Experimental Security Analysis of a Modern Automobile

Modern automobiles are no longer mere mechanical devices; they are pervasively monitored and controlled by dozens of digital computers coordinated via internal vehicular networks. While this transformation has driven major advancements in efficiency and safety, it has also introduced a range of new potential risks. In this paper we experimentally evaluate these issues on a modern automobile and demonstrate the fragility of the underlying system structure. We demonstrate that an attacker who is able to infiltrate virtually any Electronic Control Unit (ECU) can leverage this ability to completely circumvent a broad array of safety-critical systems. Over a range of experiments, both in the lab and in road tests, we demonstrate the ability to adversarially control a wide range of automotive functions and completely ignore driver input\dash including disabling the brakes, selectively braking individual wheels on demand, stopping the engine, and so on. We find that it is possible to bypass rudimentary network security protections within the car, such as maliciously bridging between our cars two internal subnets. We also present composite attacks that leverage individual weaknesses, including an attack that embeds malicious code in a cars telematics unit and that will completely erase any evidence of its presence after a crash. Looking forward, we discuss the complex challenges in addressing these vulnerabilities while considering the existing automotive ecosystem.

RFIDs and secret handshakes: defending against ghost-and-leech attacks and unauthorized reads with context-aware communications

We tackle the problem of defending against ghost-and-leech (a.k.a. proxying, relay, or man-in-the-middle) attacks against RFID tags and other contactless cards. The approach we take -- which we dub secret handshakes -- is to incorporate gesture recognition techniques directly on the RFID tags or contactless cards. These cards will only engage in wireless communications when they internally detect these secret handshakes. We demonstrate the effectiveness of this approach by implementing our secret handshake recognition system on a passive WISP RFID tag with a built-in accelerometer. Our secret handshakes approach is backward compatible with existing deployments of RFID tag and contactless card readers. Our approach was also designed to minimize the changes to the existing usage model of certain classes of RFID and contactless cards, like access cards kept in billfold and purse wallets, allowing the execution of secret handshakes without removing the card from ones wallet. Our techniques could extend to improving the security and privacy properties of other uses of RFID tags, like contactless payment cards.

Strengthening user authentication through opportunistic cryptographic identity assertions

User authentication systems are at an impasse. The most ubiquitous method -- the password -- has numerous problems, including susceptibility to unintentional exposure via phishing and cross-site password reuse. Second-factor authentication schemes have the potential to increase security but face usability and deployability challenges. For example, conventional second-factor schemes change the user authentication experience. Furthermore, while more secure than passwords, second-factor schemes still fail to provide sufficient protection against (single-use) phishing attacks. We present PhoneAuth, a system intended to provide security assurances comparable to or greater than that of conventional two-factor authentication systems while offering the same authentication experience as traditional passwords alone. Our work leverages the following key insights. First, a users personal device (eg a phone) can communicate directly with the users computer (and hence the remote web server) without any interaction with the user. Second, it is possible to provide a layered approach to security, whereby a web server can enact different policies depending on whether or not the users personal device is present. We describe and evaluate our server-side, Chromium web browser, and Android phone implementations of PhoneAuth.

Lightweight server support for browser-based CSRF protection

Cross-Site Request Forgery (CSRF) attacks are one of the top threats on the web today. These attacks exploit ambient authority in browsers (eg cookies, HTTP authentication state), turning them into confused deputies and causing undesired side effects on vulnerable web sites. Existing defenses against CSRFs fall short in their coverage and/or ease of deployment. In this paper, we present a browser/server solution, Allowed Referrer Lists (ARLs), that addresses the root cause of CSRFs and removes ambient authority for participating web sites that want to be resilient to CSRF attacks. Our solution is easy for web sites to adopt and does not affect any functionality on non-participating sites. We have implemented our design in Firefox and have evaluated it with real-world sites. We found that ARLs successfully block CSRF attacks, are simpler to implement than existing defenses, and do not significantly impact browser performance.

Protected login

Despite known problems with their security and ease-of-use, passwords will likely continue to be the main form of web authentication for the foreseeable future. We define a certain class of password-based authentication protocols and call them protected login. Protected login mechanisms present reasonable security in the face of real-world threat models. We find that some websites already employ protected login mechanisms, but observe that they struggle to protect first logins from new devices --- reducing usability and security. Armed with this insight, we make a recommendation for increasing the security of web authentication: reduce the number of unprotected logins, and in particular, offer opportunistic protection of first logins. We provide a sketch of a possible solution.

High stakes: designing a privacy preserving registry

This paper details our experience designing a privacy preserving medical marijuana registry. In this paper, we make four key contributions. First, through direct and indirect interaction with multiple stakeholders like the ACLU of Washington, law enforcement, the Cannabis Defense Coalition, state legislators, lawyers, and many others, we describe a number of intersting technical and socially-imposed challenges for building medical registries. Second, we identify a new class of registries called unidirectional, non-identifying (UDNI) registries. Third, we use the UDNI concept to propose holistic design for a medical marijuana registry that leverages elements of a central database, but physically distributes proof-of-enrollment capability to persons enrolled in the registry. This design meets all of our goals and stands up in the face of a tough threat model. Finally, we detail our experience in transforming a technical design into an actual legislative bill.