SRM seminar

Abstracts 2016

Speaker: Yuyi Wang
Title: Variable-Version Lovász Local Lemma: Beyond Shearer's Bound
Abstract: A tight criterion under which the abstract version Lovász Local Lemma (abstract-LLL) holds was given by Shearer decades ago. However, little is known about that of the variable version LLL (variable-LLL) where events are generated by independent random variables, though this model of events is applicable to almost all applications of LLL. We introduce a necessary and sufficient criterion for variable-LLL, in terms of the probabilities of the events and the event-variable graph specifying the dependency among the events. Based on this new criterion, we obtain boundaries for two families of event-variable graphs, namely, cyclic and treelike bigraphs. These are the first two non-trivial cases where the variable-LLL boundary is fully determined. As a byproduct, we also provide a universal constructive method to find a set of events whose union has the maximum probability, given the probability vector and the event-variable graph. Though it is #P-hard in general to determine variable-LLL boundaries, we can to some extent decide whether a gap exists between a variable-LLL boundary and the corresponding abstract-LLL boundary. In particular, we show that the gap existence can be decided without solving Shearer's conditions or checking our variable-LLL criterion. Equipped with this powerful theorem, we show that there is no gap if the base graph of the event-variable graph is a tree, while gap appears if the base graph has an induced cycle of length at least 4. The problem is almost completely solved except when the base graph has only 3-cliques, in which case we also get partial solutions. A set of reduction rules are established that facilitate to infer gap existence of an event-variable graph from known ones. As an application, various event-variable graphs, in particular combinatorial ones, are shown to be gapful/gapless.

Speaker: Hugues Mandon
Title: Temporal Reprogramming in Boolean Networks
Abstract: In Cellular Reprogramming, an important issue is to find which transcription factor to introduce in the cell. To find the key genes to perturb, most methods focus on finding a lot of perturbations to make in the initial state of the system, and wait for the system to reach the wanted attractor. However, waiting between smaller perturbations can be a better choice. This method is called "Temporal reprogramming". The talk will quickly explain a method to model the cell, how to find the minimum number of perturbations to do to go from one attractor to an other, and why is the scale a problem, with possible heuristics to reduce computation times.

Speaker: Tim Willemse
Title: Explorations of Attribute-Based Access Control
Abstract: Attribute-Based Access Control (ABAC) is emerging as the de facto paradigm for the specification and enforcement of access control policies. Nonetheless, ABAC is vulnerable to attribute hiding attacks where users can obtain a more favourable decision by hiding some of their attributes. The extended evaluation of an ABAC policy takes such attribute hiding into account and arguably allows to come to more precise decisions. An extended evaluation of a given query is calculated using the evaluation of all (sensible) queries that can be constructed from that query. Evidently, this approach may require exploring the state space for all possible queries; as such, evaluating a query may not be particularly efficient. In this talk we explore various techniques for computing the extended evaluation.

Speaker: Alexandre Bartel
Title: Automatically Detecting Malware: Dream or Reality?
Abstract: Malware detection techniques have been developed since at least the 1990 where "generic virus detectors" used features of benign and infected programs to spot malware. While machine learning has its advantages, it is still not clear whether the approach is appropriate to detect malware efficiently and accurately. In this presentation we will discuss the pros and cons of such approaches by looking very closely at how actual real world Android malware work.

Speaker: Ross Horne
Title: Specialisation of Attack Trees with Sequential Refinement
Abstract: Attack trees are a model that can be employed during security risk assessment. In attack trees, goals in an attack scenario are refined into sub-goals and relationship between sub-goals are depicted. In causal attack trees, some sub-goals are related by causal dependencies where one sub-goal can be causally dependent on another. In methodologies employing attack trees, the trees themselves are expected to evolve; as domain knowledge of the attack improves, or new scenarios are assessed by pruning and combining existing trees. As trees evolve it is useful to know whether one tree preserves properties depicted by another tree. In order to compare attack trees, we introduce criteria for one tree specialising another tree and also a logical mechanism for deciding such specialisations. The decision mechanism we introduce for causal attack trees is based on a recent advance in logic that I will provide a gentle introduction to in this talk.

Speaker: Yang Zhang
Title: walk2friends: Inferring social links from mobility profiles
Abstract: The development of positioning technologies has resulted in an increasing amount of mobility data being available. While bringing a lot of convenience to people's life, such availability also raises serious concerns about privacy. In this paper, we concentrate on one of the most sensitive information that can be inferred from mobility data, namely social relationships. We propose a novel social relation inference attack that relies on an advanced feature learning technique to automatically summarize users' mobility features. Compared to existing approaches, our attack is able to predict any two individuals' social relation, and it does not require the adversary to have any prior knowledge on existing social relations. These advantages significantly increase the applicability of our attack and the scope of the privacy assessment. Extensive experiments conducted on a large dataset demonstrate that our inference attack is effective, and achieves between 13% to 20% improvement over the best state-of-the-art scheme. We propose three defense mechanisms -- hiding, replacement and generalization -- and evaluate their effectiveness for mitigating the social link privacy risks stemming from mobility data sharing. Our experimental results show that both hiding and replacement mechanisms outperform generalization. Moreover, hiding and replacement achieve a comparable trade-off between utility and privacy, the former preserving better utility and the latter providing better privacy.

Speaker: Zhiqiang Zhong
Title: User profile and online recommendation system
Abstract: The recommendation system is a necessary part of media/e-commerce website. With the development of big data, the classific "Breaking News" couldn't satisfy clients anymore. We need to provide accurate personal recommendations to each client. Nowadays, there are two kinds of recommendation systems, On-line, and Off-line. I will talk about one on-line system and share my experiences about how to guarantee its accuracy and speed. At last, I will talk my ideas about using the Streaming data structure to make the system more real time.

Speaker: Guozhu Meng
Title: Guided, Stochastic Model-based GUI Testing of Android Apps
Abstract: Mobile apps are ubiquitous, operate in complex environments and are developed under the time-to-market pressure. Ensuring their correctness and reliability thus becomes an important challenge. This paper introduces Stoat, a novel guided approach to perform stochastic model-based testing on Android apps. Stoat operates in two phases: (1) Given an app as input, it uses dynamic analysis enhanced by a weighted UI exploration strategy and static analysis to reverse engineer a stochastic model of the app's GUI interactions; and (2) it adapts Gibbs sampling to iteratively mutate/refine the stochastic model and guides test generation from the mutated models toward achieving high code and model coverage and exhibiting diverse sequences. During testing, system-level events are randomly injected to further enhance the testing effectiveness. Stoat was evaluated on 93 open-source apps. The results show (1) the models produced by Stoat cover 17~31% more code than those by existing modeling tools; (2) Stoat detects 3X more unique crashes than two state-of-the-art testing tools, Monkey and Sapienz. Furthermore, Stoat tested 1661 most popular Google Play apps, and detected 2110 previously unknown and unique crashes. So far, 43 developers have responded that they are investigating our reports. 20 of reported crashes have been confirmed, and 8 already fixed.

Speaker: Borce Stojkovski
Title: Down the road
Abstract: The automotive industry along with governments and other stakeholders are paving the way to increased automation on the roads and in the vehicles. While the major focus of research in this area has been on the underlying technological aspects, sensor systems, algorithms etc., an ever-growing number of scholars, industry actors and policy-makers are advocating and calling for further investigations into human factors, still a rather complex and under-explored domain in this context. From the perspective of a human-technology teamwork, i.e. automation that enhances people versus automation that replaces people, this talk will present possible socio-technical investigations and questions of interest which are at the intersection with computer security, another highly-relevant and pertinent field, given the inherent and imminent security challenges associated with the automated and connected components and systems in the vehicles.

Speaker: Ioana Boureanu
Title: Breaking and fixing HB+DB: A Short Tale of Provable vs. Experimental Security and Lightweight Designs
Abstract: HB+ is a well-know authentication scheme purposely designed to be lightweight. However, HB+ is vulnerable to a key-recovery, man-in-the-middle (MiM) attack dubbed GRS. To this end, at WiSec2015, the HB+DB protocol added a distance-bounding dimension to HB+, which was experimentally shown to counteract the GRS attack.

In this talk, we will exhibit however a number of security flaws in the HB+DB protocol. Some attacks are authentication-driven, others relate to distance-bounding. What is more, we will show that a small refinement on the GRS-strategy still leads to key-recovery in HB+DB, un-deterred by its distance-bounding dimension. We will also propose a new distance-bounding protocol called BLOG, which is based on HB+DB but which is provably secure, enjoys better (asymptotical) security and is more lightweight.

Speaker: Steve Kremer
Title: Deciding behavioral equivalences in the applied pi calculus: complexity, procedures and tool
Abstract: We study the automated verification of behavioral equivalences in the applied pi calculus. This problem plays an essential role in formal, symbolic analysis of cryptographic protocols. We establish new complexity results for static equivalence, trace equivalence and labelled bisimilarity and propose a new decision procedure for these equivalences in the case of a bounded number of sessions. Our procedure is the first tool to decide trace equivalence and labelled bisimilarity exactly for a family of equational theories, namely those that can be represented by a subterm convergent destructor rewrite system. Finally, we implement the procedure in a new tool, called deepsec and demonstrate the applicability of the tool on several case studies.

Speaker: Cheng-Te Li
Title: Selecting Workers to Reduce Labor Force in Crowdsourcing Translation
Abstract: Crowdsourcing machine translation shows advantages of lower expense in money to collect the translated data. Yet, when compared with translation by trained professionals, results collected from non-professional translators might yield low-quality outputs. A general solution for crowdsourcing practitioners is to employ a large amount of labor force to gather enough redundant data and then solicit from it. Actually we can further save money by avoid collecting bad translations. In this talk, I will present a scoring model that estimates the quality of Turkers by their authorities based on existing translation, and then stop hiring the unqualified Turkers. We bring both opportunities and risks in crowdsourced translation: we can make it cheaper than cheaper while we might suffer from quality loss. Our model captures the intuition that good translation and good workers are mutually reinforced iteratively. The empirical studies demonstrate the model can keep the performance while reduce work force and hence cut cost in terms of BLEU score, Pearson correlation and real money.

Speaker: José Miguel Becerra
Title: On the Relation Between SIM and IND-RoR Security Models for PAKEs
Abstract: Password-based Authenticated Key-Exchange (PAKE) protocols allow users, who need only to share a password, to compute a high-entropy shared session key despite passwords being taken from a dictionary. Security models for PAKE protocols aim to capture the desired security properties that such protocols must satisfy when executed in the presence of an active adversary. They are usually classified into i) indistinguishability-based (IND-based) or ii) simulation-based (SIM-based). The relation between these two security notions is unclear and mentioned as a gap in the literature. In this work, we prove that SIM-BMP security from Boyko et al. (EUROCRYPT 2000) implies IND-RoR security from Abdalla et al. (PKC 2005) and that IND-RoR security is equivalent to a slightly modified version of SIM-BMP security. We also investigate whether IND-RoR security implies (unmodified) SIM-BMP security.

Speaker: Dinghao Wu
Title: CacheD: Identifying Cache-Based Timing Channels in Production Software
Abstract: Side-channel attacks recover secret information by analyzing the physical implementation of cryptosystems based on non-functional computational characteristics, such as time, power, and memory usage. Among all well-known side channels, cache-based timing channels are notoriously severe, leading to practical attacks against certain implementations of theoretically secure crypto algorithms, such as RSA, ElGamal and AES. Such attacks target the hierarchical design of the modern computer memory system, where different memory access patterns of a program can bring observable timing difference.

In this talk, I will present a technique to help software developers identify potential vulnerabilities that can lead to cache-based timing attacks. Our technique leverages symbolic execution and constraint solving to detect potential cache differences at each program point. We adopt a cache model that is general enough to capture various threat models that are employed in practical timing attacks. Our modeling and analysis are based on the formulation of cache access at different program locations along execution traces. We have implemented the proposed technique as a practical tool named CacheD (Cache Difference), and evaluated CacheD towards multiple real-world cryptosystems. CacheD takes less than 17 CPU hours to analyze 9 widely used cryptographic algorithm implementations with over 120 million instructions in total. The evaluation results show that our technique can accurately identify vulnerabilities reported by previous research. Moreover, we have successfully discovered previously unknown issues in two widely used cryptosystems, OpenSSL and Botan.

Speaker: Zhiming Zhao
Title: Time critical applications in cloud: challenges and the SWITCH approach
Abstract: Quality constraints on time critical applications require high-performance supporting infrastructure and sophisticated optimization mechanisms for developing and integrating system components. The lack of software development tools and in particular cloud-oriented programming and control models make the development and operation of time critical cloud applications difficult and costly. This talk presents the application-infrastructure cooperative development, provisioning and control approach used in the EU H2020 project SWITCH: the Software Workbench for Interactive, Time Critical and Highly self-adaptive cloud applications. Using this approach, application quality of service and experience, together with the programmability and controllability of cloud environments, is explicitly included at all three phases of development, deployment and run-time control in the application life-cycle.

Speaker: Yvo Desmedt
Title: Internet Voting on Insecure Platforms
Abstract: Due to massive hacking and the Snowden leak, the public at large is aware that modern computers and “secure” communication over the Internet cannot be fully trusted. The research on booth based voting (where one can trust the voting equipment) has been going on for more than 35 years. However, the legislature and the public want voting over the Internet. In such a setting, to be realistic, one has to assume the voter's platform might be hacked.
Chaum introduced code voting as a solution for using a possibly infected-by-malware device to cast a vote in an electronic voting application. He trusted the postal mail system. However, a conspiracy between the mail system and the recipient of the cast ballots breaks privacy. Moreover Chaum's system is also unpopular because the voting procedure is different from what is currently used.

To deal with these problems, we consider a t-bounded passive adversary and we remove the trust in the mail system. We propose both single and multi-seat elections, using PSMT (Perfectly Secure Message Transmission) protocols where with the help of visual aids, humans can carry out mod 10 addition correctly with a 99% degree of accuracy. We introduce an unconditionally secure MIX based on the combinatorics of set systems. We also briefly discuss how to extend this work to include active adversaries.

Speaker: Jean-Louis Huynen
Title: From Situation Awareness to Action: An Information Security Management Toolkit for Socio-Technical Security Retrospective and Prospective Analysis
Abstract: Inspired by the root cause analysis procedures common in safety, we propose a methodology for a prospective and a retrospective analysis of security and a tool that implements it. When applied prospectively, the methodology guides analysts to assess socio-technical vulnerabilities in a system, helping them to evaluate their choices in designing security policies and controls. But the methodology works also retrospectively. It assists analysts in retrieving the causes of an observed socio-technical attack, guiding them to understand where the information security management of the system has failed. The methodology is tuned to find causes that root in the human-related factors that an attacher can exploit to execute its intrusion.

Speaker: Stanislav Dashevskyi
Title: Security Assessment of Third-party Open Source Applications
Abstract: Free and Open Source Software (FOSS) components are ubiquitous in both proprietary and open source applications. In this talk we will discuss challenges that large software vendors face when they integrate FOSS components into their software supply chain. In fact, each time a vulnerability in a FOSS component is disclosed, a software vendor must decide whether to update the component, patch the application itself, or just do nothing as the vulnerability is not applicable to the deployed version that may be old enough to be not vulnerable. This is particularly challenging for enterprise software vendors that consume thousands of FOSS components, and offer more than a decade of support and security fixes for their applications.

At first we discuss a framework for performing security vulnerability experimentations, in particular, for testing known exploits for publicly disclosed vulnerabilities and adapting them as automatically as possible for different versions, configurations and environments. Second, for quickly identifying the versions of FOSS components likely affected by newly disclosed vulnerabilities, we provide an automatic screening test. This is a novel method that scans across the entire repository of FOSS component in a matter of minutes. We show that our screening test scales to large open source projects (e.g., Apache Tomcat). Finally, for facilitating the global security maintenance planning of a large portfolio of FOSS components, we discuss various models for the impact of their various characteristics on the effort for security maintenance, and empirically identify the key drivers.

Speaker: Robert Künnemann
Title: Towards a Game-theoretic Notion of Incoercibility
Abstract: Coercion is an inherently game-theoretic process: the coercer threatens punishment in the hope that a rational player will then deviate from his original plans and obey the coercer. Previous definitions simplify matters by focussing of the indistinguishability of a player that obeys the coercer, to one that deceives the coercer by simulating compliance while following his own objective, e.g., casting a vote. However, this comes at a loss of expressiveness when the goal is to quantify the amount of coercion resistance that, e.g., an electronic voting protocol provides. We introduce a framework for a game-theoretic treatment of the problem and point out that, even in an ideal vote, the small size of a voting district does indeed make voters for fringe parties vulnerable to coercion. We present our initial definition, which we unfortunately found out to be too restrictive, and discuss potential solutions.

Speaker: Man Ho Au
Title: Ring Signature and its Blockchain-related Applications
Abstract: Introduced in 2001, ring signatures are a type of anonymous digital signature. Verifiers know that the signer is a member of a group, yet they do not know the identity of the real signer. Another distinctive feature of ring signatures is that group formation is ad-hoc and does not require any coordination among users. These unique properties make it an attractive tool for privacy-friendly applications related to the blockchain. In this talk, I will cover the concept of ring signatures and its variant, linkable ring signatures. Technical constructions and applications will then be reviewed. Finally, I will relate linkable ring signatures to Monero, one of the most popular blockchain-based crypto-currencies. In particular, I will discuss how Monero utilises ring signatures for confidential transactions. To conclude the talk, I will also present other applications of ring signatures related to the blockchain.

Speaker: Ben Smyth
Title: Hacking voting systems for cash, fun, and power
Abstract: Traditional, paper-based voting systems are reliant on extensive trust assumptions. Unfortunately, instead of being trustworthy, many systems are vulnerable to attacks that could bring elections into disrepute. The shift to electronic voting systems has largely exasperated this problem. In this talk, I will show how cryptography can be used to *secure* the voting systems we use in real-life, eliminating the need for blind trust. First, I will present an informal introduction to electronic voting. Secondly, I will review the Helios electronic voting system, and highlight known attacks. Finally, I will present computational definitions of ballot secrecy and verifiability, and show that Helios can be patched to satisfy these definitions. The talk is based upon papers with David Bernhard, Michael Clarkson, Véronique Cortier, Steven Frink, and Maxime Meyer (see http://bensmyth.com/publications.php for details).

Speaker: David Naccache
Title: Where There Is Power There Is Resistance: Designing Optically Undetectable Analog Trojans
Abstract: The increased improvements in hardware trojan detection techniques stimulate the search for smaller and stealthier trojans. This article describes a minimalistic hardware trojan consisting of... a single resistor. Let $A,B$ be two conductive points in a target circuit and assume that an attacker can connect $A$ and $B$ through a resistor. All else being equal, when $A\neq B$ the target's power consumption will increase and hence leak $A\oplus B$. Depending on the exact role of $A$ and $B$, it turns out that $A\oplus B$ frequently suffices to break several popular cryptosystems. We describe the trojans' electronic structure, provide hardware simulation results, present attacks on several cryptosystems and discuss possible countermeasures. At the end of the talk I will take advantage of time left (if any :-) to expose new research ideas that can give birth to cooperation.

Speaker: Chengyi Zhang
Title: Unifying Access Control and Information Flow
Abstract: We introduce a novel security model, based on Dual Access Label (DAL) to capture information-based security requirements of programs written in these languages. DAL labels extend the access control model by specifying both the accessibility and capability of program code, and use them to constrain information flow between code from different sources. DAL's security policy places a two-way obligation on both ends of information flow so that they must have sufficient capability to meet the accessibility of each other.

Speaker: Cheng-Te Li
Title: Planning and Predicting Activities on Location-based Social Networks
Abstract: Location-based social networks depict the interactions between individuals in geography. With the popularity of online location services, such as Facebook, Foursquare, and Instagram, we are able to collect large-scale geo-social data via web crawlers. Based on geo-social big data, in this talk, I would like to share my research on planning and predicting geo-social activities in networks. This talk consists of two parts. The first is to planning itinerary activities that satisfy user requirements. I will demonstrate how to planning itineraries via a time-aware route goodness measure and a recommendation mechanism. The second aims at uncovering why users participant in geo-social activities, and predicting who will participate in the social activity organized by a certain host.

Speaker: Richard Clayton
Title: Brute Force Basics
Abstract: Classically, the effort to brute force a password was measured by some simple mathematical sums – length, character set, etc. However, that's never really been how passwords are brute forced in practice. This talk explains the approaches currently being taken by cyber-criminals to obtain credentials for a range of different services – and the practical defences that need to be deployed to thwart them.

Speaker: Hongyang Qu
Title: A stochastically verifiable autonomous control architecture with reasoning
Abstract: A new agent architecture called Limited Instruction Set Agent (LISA) is introduced for autonomous control. The new architecture is based on previous implementations of AgentSpeak and it is structurally simpler than its predecessors with the aim of facilitating design-time and run-time verification methods. The process of abstracting the LISA system to two different types of discrete probabilistic models (DTMC and MDP) is investigated and illustrated. The LISA system provides a tool for complete modelling of the agent and the environment for probabilistic verification. The agent program can be automatically compiled into a DTMC or a MDP model for verification with PRISM. The automatically generated PRISM model can be used for both design-time and run-time verification. The run-time verification is investigated and illustrated in the LISA system as an internal modelling mechanism for prediction of future outcomes.

Speaker: Gergei Bana
Title: Computationally Sound Security Analysis with First Order Logic – Computationally Complete Symbolic Attacker Based on Indistinguishability
Abstract: The computationally complete symbolic attacker is a technique that was created as a way to find all possible attacks a probabilistic polynomial time adversary can carry out on a protocol, using symbolic methods. In this talk, we first briefly review the idea of verifying complexity-theoretic security guarantees with symbolic techniques, and mention attempts of various research groups to achieve this goal. We then present the elements of our computationally complete symbolic attacker based on indistinguishability, and show how convenient it is to formalize in this framework standard complexity-theoretic hardness assumptions and cryptographic security notions such as the DDH assumption, CPA, CCA security, or unforgeability. Finally we indicate what proofs we have carried out so far for anonymity, real-or-random secrecy, agreement and authentication, and present some attacks we detected with this technique.

Speaker: Yury Zhauniarovich
Title: Small Changes, Big Changes: An Updated View on the Android Permission System
Abstract: Since the appearance of Android, its permission system was central to many studies of Android security. For a long time, the description of the architecture provided by Enck et al. in the seminal work "Understanding Android Security" was immutably used in various research papers. The introduction of highly anticipated runtime permissions in Android 6.0 forced us to reconsider this model. To our surprise, the permission system evolved with almost every release. After analysis of 16 Android versions, we can confirm that the modifications, especially introduced in Android 6.0, considerably impact the aptness of old conclusions and tools for newer releases. For instance, since Android 6.0 some signature permissions, previously granted only to apps signed with a platform certificate, can be granted to third-party apps even if they are signed with a non-platform certificate; many permissions considered before as threatening are now granted by default. In this talk, we review in detail the updated system, introduced changes, and their security implications. We will highlight some bizarre behaviors, which may be of interest for developers and security researchers.

Speaker: Matthijs Melissen
Title: An Ethical Hacker's Diary
Abstract: As an ethical hacker for the Dutch company Computest, my job consists of assessing the security of our client's systems, often by breaking into their systems. In this talk, I will demonstrate what my job entails by means of an interactive demo in which I guide the audience through the task of attacking a web application. The audience will learn about common vulnerabilities often found in real-life web applications, as well as methods to detect these vulnerabilities. This presentation will also be particularly relevant to MSc students considering a job in the security testing industry.

Speaker: Wojtek Jamroga
Title: Towards Model Checking of Coercion Resistance in Logics of Strategic Ability
Abstract: Properties of receipt-freeness, coercion resistance, and voter verifiability refer to the existence (or nonexistence) of an appropriate strategy for the voter, the coercer, or both. One can try to specify such properties by formulae of a suitable strategic logic, such as ATLir. However, automated verification of strategic properties in scenarios with partial observability is notoriously hard, and novel techniques are needed to overcome the complexity.

Speaker: Hauke Busch
Title: Boolean Modeling Reveals the Necessity of Transcriptional Regulation for Cellular Decisions
Abstract: Cellular decisions are complex processes that are controlled through the time-sequential feedback regulation of protein signaling and gene regulation. Here we use a Boolean model approach to simulate the signaling pathways, transcriptional response and feedback regulation involved in the cellular decision towards differentiation and migration from initial stimulation to the phenotype. In detail, stimulation of the nerve growth factor NGF in PC12 cells has been shown to cause cell fate decisions towards either differentiation or proliferation depending on the relative activity of downstream pERK, pAKT or pJNK signaling. Comparing the time-resolved transcriptome responses of NGF- or EGF-stimulated PC12 cells over 24 hours in combination with protein and phenotype data we iteratively refined the topology of a dynamic Boolean model to capture the temporal sequence of protein signaling, transcriptional response and subsequent autocrine feedback. Model simulations confirmed the parallel use of MAPK/ERK, PI3K/AKT and JNK/JUN for PC12 cell differentiation. As suggested in silico and confirmed in vitro, differentiation was substantially suppressed under JNK inhibition, yet delayed only under MEK/ERK inhibition. Most importantly, we found that positive transcriptional feedback induces bistability in the cell fate switch. De novo gene expression was necessary to activate autocrine feedback that caused Urokinase-Type Plasminogen Activator (UPA) Receptor signaling to perpetuate the MAPK activity, finally resulting in the expression of late, differentiation related genes. In the context of cell migration, we applied Boolean modeling to elucidate time-sequential feedback regulation of protein signaling and gene regulation of primary human keratinocytes upon hepatocyte growth factor (HGF) stimulation. Model simulations highlight the necessity of a temporal sequence of initial, transient MET receptor (met proto-oncogene, hepatocyte growth factor receptor) and subsequent, continuous epidermal growth factor/integrin signaling to trigger and sustain migration by autocrine signaling that is integrated through the Focal adhesion kinase protein. Both examples reveal that cellular decisions are established on transcriptome-induced positive feedback between protein signaling and gene expression.

Speaker: Zhe Liu
Title: microFourQ: FourQ Crypto on 8/16/32-bit Embedded Devices
Abstract:We present high-speed implementations of 128-bit secure Diffie-Hellman key exchange on a wide variety of embedded devices using the recently proposed elliptic curve FourQ. The implementations, which exhibit regular, constant-time execution to protect against timing and simple side-channel attacks, set new speed records and advance the state-of-the-art of curve-based scalar multiplication and Diffie-Hellman key exchange on 8-bit, 16-bit and 32-bit microcontrollers. For example, our implementation computes a Diffie-Hellman shared secret in 7.2 million cycles (or 0.9 seconds @8MHz) on a low-power 8-bit AVR microcontroller, which compared to the fastest Curve25519 and genus 2 Kummer implementations on the same platform, offers approximately 1.9x and 1.4x speedups, respectively. Similarly, a fully ephemeral Diffie-Hellman key exchange using 32-byte public keys is computed in only 10.8 million cycles (or 1.35 seconds @8MHz), which is approximately 2.6x and 1.8x faster than the aforementioned implementations, respectively. These results demonstrate the potential of deploying FourQ on constrained, low-power applications such as protocols for the Internet of Things (IoT).

Speaker: Vincenzo Iovino
Title: Unconditional and Efficient NIZK proofs in the Random Oracle Model
Abstract: To construct efficient Non-Interactive Zero-Knowledge (NIZK) systems, a popular and widely adopted methodology is the Fiat-Shamir’s heuristic that transforms public coin proof systems in non-interactive ones with proof of security backed in the random oracle model. The disadvantage of the FS’ transformation is that it results in NIZK arguments (i.e., non-interactive systems in which the soundness holds only against polynomial-time provers). We propose a new transformation from public coin proof systems to NIZKs that retains the efficiency of FS (around only 5 times less efficient for practical statements) but leads to proofs, and hence it is secure even against computationally unbounded provers. Additionally, we show that the random oracle can be "de-randomized" and removed to get perfect soundness in the standard model. Our result also provides practical improvements when a NIZK obtained by our transformation is instantiated with a concrete hash function. For instance, if the starting proof system has challenges of length k (with k security parameter) and first messages of length 2k then the FS’ transform is completely insecure against adversaries running in time 2^{3k} , whereas ours is secure against such adversaries assuming appropriate sub-exponential security for the hash function. Our technique is inspired by the idea of reverse randomization used in the celebrated Lautemann's proof that BPP is contained in the second level of the hierarchy that has found several other applications in cryptography.

Speaker: Johannes Müller
Title: sElect: A Lightweight Verifiable Remote Voting System
Abstract: Modern remote electronic voting systems, such as the prominent Helios system, are designed to provide vote privacy and verifiability, where, roughly speaking, the latter means that voters can make sure that their votes were actually counted. In this talk, we present a new practical voting system called sElect (secure/simple elections). This system, which we implemented as a platform independent web-based application, is meant for low-risk elections and is designed to be particularly simple and lightweight in terms of its structure, the cryptography it uses, and the user experience. One of the unique features of sElect is that it supports fully automated verification, which does not require any user interaction and is triggered as soon as a voter looks at the election result. Despite its simplicity, we prove that this system provides a good level of privacy, verifiability, and accountability for low-risk elections.

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