Metamorphic testing as a test case selection strategy

Abstract not available

A Tractable Fault Detection and Isolation Approach for Nonlinear Systems with Probabilistic Performance

This article presents a novel perspective along with a scalable methodology to design a fault detection and isolation (FDI) filter for high dimensional nonlinear systems. Previous approaches on FDI problems are either confined to linear systems or they are only applicable to low dimensional dynamics with specific structures. In contrast, shifting attention from the system dynamics to the disturbance inputs, we propose a relaxed design perspective to train a linear residual generator given some statistical information about the disturbance patterns. That is, we propose an optimization-based approach to robustify the filter with respect to finitely many signatures of the nonlinearity. We then invoke recent results in randomized optimization to provide theoretical guarantees for the performance of the proposed filer. Finally, motivated by a cyber-physical attack emanating from the vulnerabilities introduced by the interaction between IT infrastructure and power system, we deploy the developed theoretical results to detect such an intrusion before the functionality of the power system is disrupted

On Communication Complexity of Fixed Point Computation

Brouwer's fixed point theorem states that any continuous function from a compact convex space to itself has a fixed point. Roughgarden and Weinstein (FOCS 2016) initiated the study of fixed point computation in the two-player communication model, where each player gets a function from $[0,1]^n$ to $[0,1]^n$, and their goal is to find an approximate fixed point of the composition of the two functions. They left it as an open question to show a lower bound of $2^{\Omega(n)}$ for the (randomized) communication complexity of this problem, in the range of parameters which make it a total search problem. We answer this question affirmatively. Additionally, we introduce two natural fixed point problems in the two-player communication model. $\bullet$ Each player is given a function from $[0,1]^n$ to $[0,1]^{n/2}$, and their goal is to find an approximate fixed point of the concatenation of the functions. $\bullet$ Each player is given a function from $[0,1]^n$ to $[0,1]^{n}$, and their goal is to find an approximate fixed point of the interpolation of the functions. We show a randomized communication complexity lower bound of $2^{\Omega(n)}$ for these problems (for some constant approximation factor). Finally, we initiate the study of finding a panchromatic simplex in a Sperner-coloring of a triangulation (guaranteed by Sperner's lemma) in the two-player communication model: A triangulation $T$ of the $d$-simplex is publicly known and one player is given a set $S_A\subset T$ and a coloring function from $S_A$ to $\{0,\ldots ,d/2\}$, and the other player is given a set $S_B\subset T$ and a coloring function from $S_B$ to $\{d/2+1,\ldots ,d\}$, such that $S_A\dot\cup S_B=T$, and their goal is to find a panchromatic simplex. We show a randomized communication complexity lower bound of $|T|^{\Omega(1)}$ for the aforementioned problem as well (when $d$ is large)

The crisis of the refugee: an exploration of why nations have chosen to either admit or prohibit refugees entrance in times of crisis

Refugee policies are the policies that are most sensitive to times of crisis. Refugee outcomes are largely determined by the immigration policies that they face in host nations during times of conflict. Political scientists have answered the question, “How is refugee policy formed?” and have arrived at the two avenues by which refugee policies are formed. These two avenues are isolated government action and public opinion. Few have examined the possible causal forces behind the actions taken within each avenue. This analysis aims to shed light on the forces that drive isolated government action such as security concerns and ideology held by government officials, as well as the forces that drive public opinion such as racial and cultural differences and the perceived economic impact of refugees acceptance in the host nation. The exploration of these possible causal factors can help to isolate similarities across nations, crises, and time. If similarities are present, then it is possible to formulate effective solutions that target these causal factors

Compact E-Cash and Simulatable VRFs Revisited

Abstract. Efficient non-interactive zero-knowledge proofs are a powerful tool for solving many cryptographic problems. We apply the recent Groth-Sahai (GS) proof system for pairing product equations (Eurocrypt 2008) to two related cryptographic problems: compact e-cash (Eurocrypt 2005) and simulatable verifiable random functions (CRYPTO 2007). We present the first efficient compact e-cash scheme that does not rely on a random oracle. To this end we construct efficient GS proofs for signature possession, pseudo randomness and set membership. The GS proofs for pseudorandom functions give rise to a much cleaner and substantially faster construction of simulatable verifiable random functions (sVRF) under a weaker number theoretic assumption. We obtain the first efficient fully simulatable sVRF with a polynomial sized output domain (in the security parameter).

Public-Key Encryption Indistinguishable Under Plaintext-Checkable Attacks

Indistinguishability under chosen-ciphertext attack (INDCCA) is now considered the de facto security notion for public-key encryption. However, this sometimes offers a stronger security guarantee than what is needed. In this paper, we consider a weaker security notion, termed indistinguishability under plaintext-checking attacks (INDPCA), in which the adversary has only access to an oracle indicating whether or not a given ciphertext encrypts a given message. After formalizing this notion, we design a new public-key encryption scheme satisfying it. The new scheme is a variant of the Cramer-Shoup encryption scheme with shorter ciphertexts. Its security is also based on the plain Decisional Diffie-Hellman (DDH) assumption. Additionally, the algebraic properties of the new scheme allow proving plaintext knowledge using Groth-Sahai non-interactive zero-knowledge proofs or smooth projective hash functions. Finally, as a concrete application, we show that, for many password-based authenticated key exchange (PAKE) schemes in the Bellare-Pointcheval-Rogaway security model, we can safely replace the underlying INDCCA encryption schemes with our new INDPCA one. By doing so, we reduce the overall communication complexity of these protocols and obtain the most efficient PAKE schemes to date based on plain DDH

A revisit of three studies related to random testing

Software testing is an approach that ensures the quality of software through execution, with a goal being to reveal failures and other problems as quickly as possible. Test case selection is a fundamental issue in software testing, and has generated a large body of research, especially with regards to the effectiveness of random testing (RT), where test cases are randomly selected from the software’s input domain. In this paper, we revisit three of our previous studies. The first study investigated a sufficient condition for partition testing (PT) to outperform RT, and was motivated by various controversial and conflicting results suggesting that sometimes PT performed better than RT, and sometimes the opposite. The second study aimed at enhancing RT itself, and was motivated by the fact that RT continues to be a fundamental and popular testing technique. This second study enhanced RT fault detection effectiveness by making use of the common observation that failure-causing inputs tend to cluster together, and resulted in a new family of RT techniques: adaptive random testing (ART), which is random testing with an even spread of test cases across the input domain. Following the successful use of failure-causing region contiguity insights to develop ART, we conducted a third study on how to make use of other characteristics of failure-causing inputs to develop more effective test case selection strategies. This third study revealed how best to approach testing strategies when certain characteristics of the failure-causing inputs are known, and produced some interesting and important results. In revisiting these three previous studies, we explore their unexpected commonalities, and identify diversity as a key concept underlying their effectiveness. This observation further prompted us to examine whether or not such a concept plays a role in other areas of software testing, and our conclusion is that, yes, diversity appears to be one of the most important concepts in the field of software testing