Locating and Securing Use-After-Free Pointers

Dangling pointers and/or use-after-free pointers are gateways to exploits for software such as browsers, operating systems, etc. To forestall attacks that rely on dangling or user-after-free pointers, ordinary pointers in source code can be replaced by secure pointers. However, rolling out code with such replacement requires the developer to incur testing and engineering costs. Further, due to the likely memory and runtime overheads of secure pointers, it is useful to identify ordinary pointers in source code that merit replacement. This disclosure describes techniques to determine which ordinary pointers in source code are suitable for replacement by secure pointers

Development of Grid-Based Direct Kinetic Method and Hybrid Kinetic-Continuum Modeling of Hall Thruster Discharge Plasmas.

Novel computational methods were developed and used to characterize plasma flows and improve the efficiency of electric propulsion devices. The focus of this doctoral research is on developing a grid-based direct kinetic (DK) simulation method that is an alternative to particle-based kinetic methods. The first part of this dissertation describes development of the grid-based direct kinetic method through verification and benchmarking. The test cases include a plasma-sheath with and without secondary electron emission from a plasma-immersed material as well as trapped particle bunching instability in nonlinear plasma waves. Using a hybrid kinetic-continuum method for the discharge plasma in a Hall effect thruster, the grid-based DK simulation and a standard particle-in-cell (PIC) method are compared. It was found that ionization events and hence ionization oscillations are captured without any statistical noise in the DK simulation in comparison to a particle simulation. In the second part, mode transition of the discharge oscillations in Hall effect thrusters, which are known to affect thruster performance, is investigated using the hybrid-DK method, in which the DK method is used for ions and a continuum method is used for electrons. The numerical simulations show good agreement with experimental data. In addition, a linear perturbation theory of ionization oscillations is derived. It is found that electron transport and temperature play an important role in such discharge oscillations whereas the common understanding in the community was that the heavy species are the main contributors. In addition, a two-dimensional simulation is developed to investigate the multidimensional ionization oscillation phenomena in the Hall effect thrusters. The effect of ion magnetization due to the magnetic field is included, showing a swirling effect of accelerated ions. Local ionization oscillations in the azimuthal direction are observed.PhDAerospace EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/111379/1/kenhara_1.pd

Web-based currency for online content and transactions

A web currency is described for settling digital transactions between parties. Users acquire web currency by outright purchase and based on user contributions. User privacy and security is enabled via the use of anonymized addresses that are mapped in a secure and private manner to a user wallet. User access of content is enabled by transmission of an address from the user\u27s wallet that is representative of a value of web currency to be transferred. Users can obtain a subscription to multiple content providers via a browser platform that enables viewing of content of participating content providers. The web currency can also be utilized for online commerce

Observing User Engagement

Content creators can be paid for user engagement by third party observers based on user engagement with their content. However, observers cannot determine user engagement when user agents do not permit access to content consumption history. This disclosure describes web-primitives that enable user agents such as browser applications to enable measurement of user engagement in a privacy-preserving manner. The described primitives are generic enough to enable third party observers to implement tokens based on user engagement, while disabling third-party access to the user’s content consumption history

Inline-Frames to Enable Zero-Friction Cross-Origin Transactions

While web-users can currently exchange virtual coins, fun tokens, loyalty points, etc., such exchanges are limited to same-origin tokens. For example, points of a game application are exchangeable only within that application. This disclosure describes techniques that utilize inline-frames to enable token exchange in a manner that is both cross-origin and zero-friction. The techniques enable users to securely and confidentially send cross-origin tokens in a single-step process as easy as clicking a like-button, without additional login or confirmation. The techniques enable websites and services to easily micro-monetize (or fun-tokenize) digital content and user activities on the web, thereby inducing a powerful network effect

Deterministic Stack Scanning to Prevent Dangling or Use-after-Free Pointers

Dangling pointers and/or use-after-free pointers are gateways to exploits for software such as browsers, operating systems, etc. To forestall attacks that rely on dangling or use-after-free (UaF) pointers, ordinary pointers in source code can be replaced by secure pointers. However, secure pointers are generally applicable to the heap, not to the stack. In the stack, there may remain dangling or UaF pointers. This disclosure describes techniques to deterministically scan the stack such that objects referenced from on-stack pointers remain unfreed, thereby preventing their conversion to use-after-free pointers

Aggregation And Display Of User-Submitted Comments In A Browser

A system and method that facilitates the sharing of user-generated content is disclosed. By way of example and as described in more detail below, a system may aggregate comments regarding a webpage from multiple users, store the comments on a different server from the website, and display the comments in a browser alongside the webpage

Automatic Sanitization of Use-After-Free Pointers

When the memory for an object is deallocated, pointers to that object become invalid. Such pointers, known as dangling pointers, can be exploited by attackers to cause undesirable or malicious program behavior. A pointer that points to memory that has been reused (reallocated) is known as a use-after-free pointer; these, too, are gateways to exploits. This disclosure describes techniques to track pointers in runtime and periodically test pointers to determine if they are pointing to deallocated or reallocated memory regions. Upon the discovery of pointers pointing to deallocated or reallocated memory, security breaches are forestalled by causing a program crash accompanied by a bug report