Phd Dissertation

Graph Neural Network for Integrated Circuits and Cyber-Physical Systems Security

Publication Date

January 1, 2023

Author(s)

Abstract

This Ph.D. dissertation presents a comprehensive investigation into addressing security and reliability challenges in embedded and Cyber-Physical Systems (CPS). Our research leverages advanced machine learning techniques such as Graph Neural Networks (GNN) to develop novel methodologies for cross-layer security analysis.This dissertation addresses the growing risk posed by the globalization of the Integrated Circuit (IC) supply chain, whereby the majority of the design, fabrication, and testing processes have been outsourced to untrusted third-party entities across the globe. This development has significantly increased the threat of malicious modifications, known as Hardware Trojans (HTs), being inserted into Third-Party Intellectual Property (3PIP). HTs pose a substantial risk to IC integrity, functionality, and performance. Despite numerous HT detection methods proposed in existing literature, most limitations include reliance on a golden reference circuit, lack of generalizability, limited detection scope, low localization resolution, and manual feature extraction and property definition. Furthermore, the equally important task of HT localization has been neglected. This research proposes an innovative, golden reference-free method for HT detection and localization at the pre-silicon stage of IC development, employing models based on GNN. The circuit design is converted into a graph that is an intrinsic data structure for hardware design and captures the computational structure and data dependencies. We develop a graph classification model to distinguish between HT-free and circuits infected with known or even unknown HTs. To push the boundaries further, we extract node attributes from the HDL code and devise a Graph Convolutional Network (GCN) that facilitates automatic feature extraction, enabling the classification of nodes as either Trojan or benign. This methodology offers an automated approach to HT detection and localization, relieving designers of the need for time-consuming manual code review. The developed method achieves exceptional performance in detecting HT-infected circuits and locating the HT. The approach outlined in this dissertation sets a new benchmark for HT detection and localization, offering a scalable, efficient, and highly accurate tool for securing the pre-silicon IC supply chain.This dissertation expands to encompass the challenges facing IP piracy. The productivity gap, coupled with time-to-market pressure, has led to increased interest in hardware Intellectual Property (IP) core design within the semiconductor industry, dramatically reducing design and verification costs. Recognizing these challenges, this dissertation proposes a novel IP piracy detection methodology, modeling circuits and assessing similarity between IP designs. Contrary to traditional methods that embed a signature within the circuit design, our method does not introduce additional hardware overhead, nor is it vulnerable to removal, masking, or forging attacks. This approach effectively exposes IP infringements, even when the original IP is complicated by the adversary to deceive the IP owner. To represent the circuit accurately for modeling, we translate the hardware design into a data-flow graph due to similar data types and properties and subsequently model it using state-of-the-art graph learning methods. This approach effectively complements the GNN-based techniques proposed earlier in this dissertation, presenting a robust and comprehensive suite of solutions for security and reliability challenges in the semiconductor industry. Moving to the CPS domain, the dissertation addresses security challenges in IoT systems through the development of adaptive anomaly detection methods. The first proposed approach utilizes IoT sensor data and fog computing to ensure data integrity and detect anomalous incidents. The proposed methodology incorporates our sensor association algorithm, LSTM neural networks, and Gaussian estimation for real-time anomaly detection. The dissertation further extends the research to multi-modal data fusion, where the integration of sensor and communication data using GNN enables improved anomaly detection, source identification, and recovery in IoT systems.Overall, this dissertation showcases the application of advanced techniques such as GNN and machine learning in enhancing security and reliability in hardware design and IoT systems. The proposed methodologies for anomaly detection, hardware Trojan detection, IP piracy detection, and cross-layer security analysis contribute to advancing the state-of-the-art in ensuring the integrity and security of critical systems in the digital era.

Suggested Citation
Rosin Yasaei (2023) Graph Neural Network for Integrated Circuits and Cyber-Physical Systems Security. PhD Dissertation. UC Irvine. Available at: https://uci.primo.exlibrisgroup.com/permalink/01CDL_IRV_INST/u4evf/cdi_proquest_journals_2854332836.

published journal article

Free transit for students to regain ridership: Users and boarding characteristics of LA Metro's GoPass program

Journal of Transport Geography

Publication Date

December 1, 2025

Abstract

The Los Angeles County Metropolitan Transportation Authority (LA Metro) started in October 2021 the largest free transit pass program in the U.S. to date. Known as GoPass, it serves students from kindergarten to community colleges in Los Angeles County, the most populated county in the U.S. Although many free transit pass programs have been created, few have been analyzed from the point of view of transit agencies (i.e., for the characteristics of their users and their impact on ridership). To address this gap, we first examine GoPass’ contribution to LA Metro’s bus boardings, before comparing selected characteristics of the students enrolled in GoPass in 2023 with census data. We find some opportunities for additional growth, including for female students. To understand GoPass usage, we estimated a generalized spatial regression model that explains annual GoPass boardings aggregated by census tract (detailed usage data are unavailable to protect the students’ privacy) using a broad range of socioeconomic and built environment variables. Our results confirm the presence of strong spatial effects. We find that census tracts with more young males, more transit stops, mixed land use, and more participating schools accessible within 30 min by transit have more GoPass boardings. Conversely, the number of GoPass boardings decreases with more access to private vehicles, property crimes, multifamily units, and a higher population density. A better understanding of the characteristics of GoPass users and GoPass usage is useful to improve GoPass and to inform transit agencies interested in creating similar programs.

Suggested Citation
Farzana Khatun and Jean-Daniel Saphores (2025) “Free transit for students to regain ridership: Users and boarding characteristics of LA Metro's GoPass program”, Journal of Transport Geography, 129, p. 104442. Available at: 10.1016/j.jtrangeo.2025.104442.

published journal article

The political economy of urban transport-system choice

Journal of Public Economics

Publication Date

August 1, 2006

Author(s)

Jan Brueckner, Harris Selod
Suggested Citation
Jan K. Brueckner and Harris Selod (2006) “The political economy of urban transport-system choice”, Journal of Public Economics, 90(6-7), pp. 983–1005. Available at: 10.1016/j.jpubeco.2005.06.004.

research report

An activity-based assessment of the potential impacts of plug-in hybrid electric vehicles on energy and emissions using one-day travel data

Abstract

The main objective of this paper is to assess the energy profile impacts of plug-in hybrid electric vehicles (PHEVs) based on simulation of vehicles used in activity and travel patterns drawn from the 2000-2001 California Statewide Household Travel Survey. Simulations replicating reported continuous one-day data are used to generate realistic energy impact assessment of PHEV market penetration. A second objective is to estimate the decreased gasoline consumption and increased electricity demand in California. The authors found that diverting charging demands to off-peak periods will not necessarily maximize energy efficiency; daytime charging will allow more trips by electricity, but will result in higher peaks for high-demand periods.

Suggested Citation
Will Recker and Jee E. Kang (2010) An activity-based assessment of the potential impacts of plug-in hybrid electric vehicles on energy and emissions using one-day travel data. University of California Transportation Center, p. 48p. Available at: https://escholarship.org/uc/item/71k7k533.

research report

A Statewide Optimal Resource Allocation Tool Using Geographic Information Systems, Spatial Analysis, and Regression Methods

Publication Date

November 1, 2008

Author(s)

Konstadinos Goulias, Thomas Golob, Sungsu (Stephen) Yoon

Final Report

UCB-ITS-PRR-2008-27

Abstract

The overall objective of this project is to develop an optimal resource allocation tool for the entire state of California using Geographic Information Systems and widely available data sources. As this tool evolves it will be used to make investment decisions in transportation infrastructure while accounting for their spatial and social distribution of impacts. Tools of this type do not exist due to lack of suitable planning support tools, lack of efforts in assembling data and information from a variety of sources, and lack of coordination in assembling the data. Suitable planning support tools can be created with analytical experimentation to identify the best methods and the first steps are taken in this project. Assembly of widely available data is also demonstrated in this project. Coordination of fragmented jurisdictions remains an elusive task that is left outside the project. When this project begun we confronted some of these issues and embarked in a path of feasibility demonstration in the form of a pilot project that gave us very encouraging results. In spite of this pilot nature aiming at demonstration of technical feasibility, substantive conclusions and findings are also extracted from each analytical step.In this project we have two parallel analytical tracks that are a statewide macroanalysis (called the zonal based approach herein) and an individual and household based microanalysis (called the person based approach herein). In the statewide macroanalysis we study efficiency and equity in resource allocation. Resources are intended as infrastructure availability and access to activity participation offered by the combined effect of transportation infrastructure and land use measured by indicators of accessibility. Stochastic frontiers are used to study efficiency and a particular type of inequality measurement called the Theil fractal inequality index is used to study equity in the macroanalysis. The outcome of this analysis are maps identifying places in California that enjoy higher levels of service when compared to the entire state and places which succeeded in allocating resources in a relatively better way than others. In the individual microanalysis we use the accessibility indicators from the macronalysis and expand them by defining a new set of indicators at a second level of spatial (dis)aggregation. Then we use them as explanatory factors of travel behavior with focus on the use of different travel models (e.g., driving alone, use of public transportation and so forth). As expected infrastructure availability and accessibility to activity opportunities has a significant and substantive effect on the use of different modes. Many resource allocation decisions, then, will impact behavior, which in turn influences the optimality and equity conditions. This implies that decisions about where and when to allocate resources in public and private transportation needs to account for changes in behavior in a dynamic fashion, using scenarios of accessibility provision and assessing their impact by studying activity and travel behavior changes.

Suggested Citation
Konstadinos G. Goulias, Thomas F. Golob and Seo Youn Yoon (2008) A Statewide Optimal Resource Allocation Tool Using Geographic Information Systems, Spatial Analysis, and Regression Methods. Final Report UCB-ITS-PRR-2008-27. Institute of Transportation Studies, Irvine. Available at: https://escholarship.org/uc/item/2gt23996.

published journal article

Traffic equilibrium problem with route-specific costs: formulation and algorithms

Transportation Research Part B: Methodological

Publication Date

August 1, 2000

Author(s)

Hong Lo, Anthony Chen

Abstract

Using a new gap function recently proposed by Facchinei and Soares [Facchinei, F., Soares, J., 1995. Testing a new class of algorithms for nonlinear complementarity problems. In: Giannessi, F., Maugeri, A. (Eds.), Variational Inequalities and Network Equilibrium Problems. Plenum Press, New York], we convert the nonlinear complementarity problem (NCP) formulation for the traffic equilibrium problem to an equivalent unconstrained optimization. This equivalent formulation uses both route flows and the minimum origin–destination travel costs as the decision variables. Two unique features of this formulation are that: (i) it can model the traffic assignment problem with a general route cost structure; (ii) it is smooth, unconstrained, and that every stationary point of the minimization corresponds to a global minimum. These properties permit a number of efficient algorithms for its solution. Two solution approaches are developed to solve the proposed formulation. Numerical results using a route-specific cost structure are provided and compared with the classic traffic equilibrium problem, which assumes an additive route cost function.

Suggested Citation
Hong K. Lo and Anthony Chen (2000) “Traffic equilibrium problem with route-specific costs: formulation and algorithms”, Transportation Research Part B: Methodological, 34(6), pp. 493–513. Available at: 10.1016/S0191-2615(99)00035-1.

MS Thesis

Assessing the Impact of SB743 on Transportation Planning, Traffic Impact Analysis, and Level-of-Service

Abstract

Since the implementation of CEQA in 1970, traffic impact analyses have been a key component in California’s land development. A current paradigm shift towards building and living sustainably has caused policy makers, engineers and planners to reexamine the policies that have been instituted. It has also influenced exploration of solutions that can change future developments. We must first analyze the established system of traffic impact analysis to determine the viability and potential benefits of measuring transportation network efficiency through factors highlighted in Senate Bill (SB) 743. These factors include vehicle miles travelled (VMT), fuel use or automobile trips generated. For the purpose of this paper, the focus will be on the VMT. When VMT analysis is applied on a project level, a list of key questions arise that are related to SB 743’s goals of reducing greenhouse gases, increasing multimodal transportation and developing appropriate metrics to conduct transportation analysis. A review of Senate Bill 743 text along with the Governor’s Office of Planning and Research report on the Bill paints a picture of what California’s future development will look like. Furthermore, an examination of travel trends and literature about current transportation analysis helps to evaluate the potential success of Senate Bill 743. In summary, Senate Bill 743 symbolizes a huge step towards carbon emission reduction and an excellent opportunity to start a conversation about making land development more sustainable in California. However, the bill leaves out the essential components of existing traffic impact analyses and employs a measure of environmental impact that does not reflect accessibility or multi-modal transportation.

Suggested Citation
Oluseyi Ojuri (2015) Assessing the Impact of SB743 on Transportation Planning, Traffic Impact Analysis, and Level-of-Service. MS Thesis. UC Irvine. Available at: https://uci.primo.exlibrisgroup.com/permalink/01CDL_IRV_INST/u4evf/cdi_proquest_journals_1773308282.

presentation

Analyzing the Impact of Land Use and Sociodemographics on Microtransit

Publication Date

October 10, 2025

Author(s)

Suggested Citation
Tim Wang (2025) “Analyzing the Impact of Land Use and Sociodemographics on Microtransit”. 2025 ITS-Irvine Emerging Scholars Transportation Research Showcase I, ITS-Irvine, 10 October. Available at: https://youtu.be/tizg3bjVN50?t=3412.

published journal article

Estimating Benefits of Same Day Delivery Services with an Integrated Activity-Based Travel Optimization Approach

Procedia Computer Science

Suggested Citation
Marjan Mosslemi, Dingtong Yang and R. Jayakrishnan (2025) “Estimating Benefits of Same Day Delivery Services with an Integrated Activity-Based Travel Optimization Approach”, Procedia Computer Science, 257, pp. 722–730. Available at: 10.1016/j.procs.2025.03.093.

published journal article

How do information ambiguity and timing of contextual information affect managers' goal congruence in making investment decisions in good times vs. Bad times?

Journal of Risk and Uncertainty

Publication Date

September 1, 2005

Author(s)

Joanna L.Y. Ho, Robin Keller, Pamela Keltyka
Suggested Citation
Joanna L.Y. Ho, L. Robin Keller and Pamela Keltyka (2005) “How do information ambiguity and timing of contextual information affect managers' goal congruence in making investment decisions in good times vs. Bad times?”, Journal of Risk and Uncertainty, 31(2), pp. 163–186. Available at: 10.1007/s11166-005-3553-8.