Today’s smartphone operating systems frequently fail to provide users with visibility into how third-party applications collect and share their private data. We address these shortcomings with TaintDroid, an efficient, system-wide dynamic taint tracking and analysis system capable of simultaneously tracking multiple sources of sensitive data. TaintDroid enables realtime analysis by leveraging Android’s virtualized execution environment. TaintDroid incurs only 32p performance overhead on a CPU-bound microbenchmark and imposes negligible overhead on interactive third-party applications. Using TaintDroid to monitor the behavior of 30 popular third-party Android applications, in our 2010 study we found 20 applications potentially misused users’ private information; so did a similar fraction of the tested applications in our 2012 study. Monitoring the flow of privacy-sensitive data with TaintDroid provides valuable input for smartphone users and security service firms seeking to identify misbehaving applications.

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TaintDroid: An Information-Flow Tracking System for Realtime Privacy Monitoring on Smartphones

Today's smartphone operating systems frequently fail to provide users with adequate control over and visibility into how third-party applications use their private data. We address these shortcomings with TaintDroid, an efficient, system-wide dynamic taint tracking and analysis system capable of simultaneously tracking multiple sources of sensitive data. TaintDroid provides realtime analysis by leveraging Android's virtualized execution environment. TaintDroid incurs only 14% performance overhead on a CPU-bound micro-benchmark and imposes negligible overhead on interactive third-party applications. Using TaintDroid to monitor the behavior of 30 popular third-party Android applications, we found 68 instances of potential misuse of users' private information across 20 applications. Monitoring sensitive data with TaintDroid provides informed use of third-party applications for phone users and valuable input for smartphone security service firms seeking to identify misbehaving applications.

/pdf/taintdroid-an-information-flow-tracking-system-for-realtime-3fnz9lwdso.pdf

TaintDroid: an information-flow tracking system for realtime privacy monitoring on smartphones

Ordered Binary-Decision Diagrams (OBDDs) represent Boolean functions as directed acyclic graphs. They form a canonical representation, making testing of functional properties such as satisfiability and equivalence straightforward. A number of operations on Boolean functions can be implemented as graph algorithms on OBDD data structures. Using OBDDs, a wide variety of problems can be solved through symbolic analysis. First, the possible variations in system parameters and operating conditions are encoded with Boolean variables. Then the system is evaluated for all variations by a sequence of OBDD operations. Researchers have thus solved a number of problems in digital-system design, finite-state system analysis, artificial intelligence, and mathematical logic. This paper describes the OBDD data structure and surveys a number of applications that have been solved by OBDD-based symbolic analysis.

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Symbolic Boolean manipulation with ordered binary-decision diagrams

Physical Unclonable Functions (PUFs) are innovative circuit primitives that extract secrets from physical characteristics of integrated circuits (ICs). We present PUF designs that exploit inherent delay characteristics of wires and transistors that differ from chip to chip, and describe how PUFs can enable low-cost authentication of individual ICs and generate volatile secret keys for cryptographic operations.

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Physical unclonable functions for device authentication and secret key generation

Physical Unclonable Functions for Device Authentication and Secret Key Generation

The most common approach to checking correctness of a hardware or software design is to verify that a description of the design has the proper behavior as elicited by a series of input stimuli. In the case of software, the program is simply run with the appropriate inputs, and in the case of hardware, its description written in a hardware description language (HDL) is simulated with the appropriate input vectors. In coverage-directed validation, coverage metrics are defined that quantitatively measure the degree of verification coverage of the design. Motivated by recent work on observability-based coverage metrics for models described in a hardware description language, we develop a method that computes an observability-based code coverage metric for embedded software written in a high-level programming language. Given a set of input vectors, our metric indicates the instructions that had no effect on the output. An assignment that was not relevant to generate the output value cannot be considered as being covered. Results show that our method offers a significantly more accurate assessment of design verification coverage than statement coverage. Existing coverage methods for hardware can be used with our method to build a verification methodology for mixed hardware/software or embedded systems.

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Observability analysis of embedded software for coverage-directed validation

Path-based, Randomized, Oblivious, Minimal routing (PROM) is a family of oblivious, minimal, path-diverse routing algorithms especially suitable for Network-on-Chip applications with n x n mesh geometry. Rather than choosing among all possible paths at the source node, PROM algorithms achieve the same effect progressively through efficient, local randomized decisions at each hop. Routing is deadlock-free in all PROM algorithms when the routers have at least two virtual channels.While the approach we present can be viewed as a generalization of both ROMM and O1TURN routing, it combines the low-hardware cost of O1TURN with the routing diversity offered by the most complex n-phase ROMM schemes. As all PROM algorithms employ the same hardware, a wide range of routing behaviors, from O1TURN-equivalent to uniformly path-diverse, can be effected by adjusting just one parameter, even while the network is live and continues to forward packets. Detailed simulation on a set of benchmarks indicates that, on equivalent hardware, the performance of PROM algorithms compares favorably to existing oblivious routing algorithms, including dimension-ordered routing, two-phase ROMM, and O1TURN.

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Path-based, randomized, oblivious, minimal routing

Oblivious RAM (ORAM) is a cryptographic primitive that hides memory access patterns to untrusted storage. ORAM may be used in secure processors for encrypted computation and/or software protection. While recursive Path ORAM is currently the most practical ORAM for secure processors, it still incurs large performance and energy overhead and is the performance bottleneck of recently proposed secure processors. In this paper, we propose two optimizations to recursive Path ORAM. First, we identify a type of program locality in its operations to improve performance. Second, we use pseudorandom function to compress the position map. But applying these two techniques in recursive Path ORAM breaks ORAM security. To securely take advantage of the two ideas, we propose unified ORAM. Unified ORAM improves performance both asymptotically and empirically. Empirically, our experiments show that unified ORAM reduces data movement from ORAM by half and improves benchmark performance by 61% as compared to recursive Path ORAM.

Unified Oblivious-RAM: Improving Recursive ORAM with Locality and Pseudorandomness.

• Advantages - significantly reduces traffic on high-locality workloads up to 14x reduction in traffic in some benchmarks - simple to implement and verify (indep. of core count, no transient states) - decentralized & trivially scalable (only # core ID bits, addr ↔ core mapping) • Challenges - workloads should be optimized with memory model in mind (like allocating data on cache line boundaries but more coarse-grained) - automatically mapping allocation over cores not a trivial problem • Opportunities - fine-grained migration is an enabling technology - since it's cheap and responsive, can be used for almost anything - e.g., if only some cores have FPUs, migrate to access FPU

Hardware-level thread migration in a 110-core shared-memory multiprocessor

We present new protocols for Byzantine state machine replication and Byzantine agreement in the synchronous and authenticated setting. The celebrated PBFT state machine replication protocol tolerates $f$ Byzantine faults in an asynchronous setting using $3f+1$ replicas, and has since been studied or deployed by numerous works. In this work, we improve the Byzantine fault tolerance to $n=2f+1$ by utilizing the synchrony assumption. The key challenge is to ensure a quorum intersection at one \emph{honest} replica. Our solution is to rely on the synchrony assumption to form a \emph{post-commit} quorum of size $2f+1$, which intersects at $f+1$ replicas with any \emph{pre-commit} quorums of size $f+1$. Our protocol also solves synchronous authenticated Byzantine agreement in fewer rounds than the best existing solution (Katz and Koo, 2006). A challenge in this direction is to handle non-simultaneous termination, which we solve by introducing a notion of \emph{virtual} participation after termination. Our protocols may be applied to build practical synchronous Byzantine fault tolerant systems and improve cryptographic protocols such as secure multiparty computation and cryptocurrencies when synchrony can be assumed.

Srinivas Devadas

Papers

Observability analysis of embedded software for coverage-directed validation

Path-based, randomized, oblivious, minimal routing

Unified Oblivious-RAM: Improving Recursive ORAM with Locality and Pseudorandomness.

Hardware-level thread migration in a 110-core shared-memory multiprocessor

Practical Synchronous Byzantine Consensus