We propose density independent hydrodynamics model (DIHM) which is a novel and automatic method for coherency detection in crowded scenes. One of the major advantages of the DIHM is its capability to handle changing density over time. Moreover, the DIHM avoids oversegmentation and thus achieves refined coherency detection. In the proposed DIHM, we first extract a motion flow field from the input video through particle initialization and dense optical flow. The particles of interest are then collected to retain only the most motile and informative particles. To represent each particle, we accumulate the contribution of each particle in a weighted form, based on a kernel function. Next, the smoothed particle hydrodynamics (SPH) is adopted to detect coherent regions. Finally, the detected coherent regions are refined to remove the effects of oversegmentation. We perform extensive experiments on three benchmark datasets and compare the results with 10 state-of-the-art coherency detection methods. Our results show that DIHM achieves superior coherency detection and outperforms the compared methods in both pixel level and coherent region level average particle error rates (PERs), average coherent number error (CNE) and F-score.

Session cookies constitute one of the main attack targets against client authentication on the Web. To counter these attacks, modern web browsers implement native cookie protection mechanisms based on the HttpOnly and Secure flags. While there is a general understanding about the effectiveness of these defenses, no formal result has so far been proved about the security guarantees they convey. With the present paper we provide the first such result, by presenting a mechanized proof of noninterference assessing the robustness of the HttpOnly and Secure cookie flags against both web and network attackers with the ability to perform arbitrary XSS code injection. We then develop CookiExt, a browser extension that provides client-side protection against session hijacking, based on appropriate flagging of session cookies and automatic redirection over HTTPS for HTTP requests carrying these cookies. Our solution improves over existing client-side defenses by combining protection against both web and network attacks, while at the same time being designed so as to minimise its effects on the user’s browsing experience. Finally, we report on the experiments we carried out to practically evaluate the effectiveness of our approach

Enforcing protection at the browser side has recently become a popular approach for securing web authentication. Though interesting, existing attempts in the literature only address specific classes of attacks, and thus fall short of providing robust foundations to reason on web authentication security. In this paper we provide such foundations, by introducing a novel notion of web session integrity, which allows us to capture many existing attacks and spot some new ones. We then propose FF+, a security-enhanced model of a web browser that provides a full-fledged and provably sound enforcement of web session integrity. We leverage our theory to develop SessInt, a prototype extension for Google Chrome implementing the security mechanisms formalized in FF+. SessInt provides a level of security very close to FF+, while keeping an eye at usability and user experience

Session cookies constitute one of the main attack targets against client authentication on the Web. To counter that, modern web browsers implement native cookie protection mechanisms based on the Secure and HttpOnly flags. While there is a general understanding about the effectiveness of these defenses, no formal result has so far been proved about the security guarantees they convey. With the present paper we provide the first such result, with a mechanized proof of noninterference assessing the robustness of the Secure and HttpOnly cookie flags against both web and network attacks. We then develop CookiExt, a browser extension that provides client-side protection against session hijacking based on appropriate flagging of session cookies and automatic redirection over HTTPS for HTTP requests carrying such cookies. Our solution improves over existing client-side defenses by combining protection against both web and network attacks, while at the same time being designed so as to minimise its effects on the user's browsing experience.

Mobile devices are an indispensable part of modern-day lives to support portable computations and context-aware communication. Android applications within a mobile device share data to support application operations and better user experience, which also increases security risks to device's data integrity and confidentiality. To analyze the security provided by the Android permissions, modern security techniques, based on the programming languages, have been used to enforce best practices for developing the secure Android applications. Android security assessment, based on the language-based techniques in an informal setting without formal tool support, is tedious and error-prone. Furthermore, the lack of proof of the soundness of the language-based techniques raises questions about the validity of the analysis. To enable computer-aided formal verification in Android security domain, we have developed a mathematical model of language-based Android security using computer-based proof assistant Coq. One of the main challenges for mechanizing the language-based security in theorem prover relates to the complexity of variable bindings in language-based security techniques. As the main contributions of the paper: 1) the language-based security, including variable binding, is formalized in theorem prover Coq; 2) a formal type checker is built to type check (capture safe data flows within) Android applications using computer; and 3) the soundness of the language-based security technique (type system) is mechanically verified. The formal model of the Android type system and their proof of soundness are machine-readable, and their correctness can be checked in the computer using Coq proof and type checkers.