About

My research focus is in the area of applied cryptography. My recent work includes developing privacy-preserving cryptographic protocols for implementing anonymous electronic cash and identification. I helped to deploy the first two private, compliant stablecoins. I have also developed protocols that allow users to access databases without revealing which data they're accessing. Additionally, I have been working on new automation techniques to assist in the design and deployment of advanced cryptographic protocols.

Research topics

• Nanotechnology
• Composite material
• Materials science

Selected publications

• The effect of Bisphenol A <i>vs</i> . Bisphenol F on the performance of polysulfone membranes

  RSC Applied Polymers · 2025-12-08

  articleOpen accessSenior author

  Systematic comparison of pBPA and pBPF polysulfone membranes reveals how backbone structure, molecular weight, and casting concentration govern permeance and mechanical properties.

  PublisherOA PDFDOI

• ID# 1904319 Novel Neuromodulation System for the Treatment of Chronic Migraine: Preliminary Results from the RELIEV-CM Study

  Neuromodulation Technology at the Neural Interface · 2025-09-23

  article1st authorCorresponding
  PublisherDOI

• Tuning the Surface Properties and Biofouling Resistance of Fluorinated Siloxane Copolymers

  Langmuir · 2025-05-15

  articleSenior authorCorresponding

  This study explores the suitability of fluorinated polysiloxanes in medical applications through biofouling studies with Escherichia coli MG1655 (E. coli) and Pseudomonas aeruginosa PAO1 (P. aeruginosa). Commercially available fluorinated poly(dimethylsiloxane) poly(trifluoropropyl methylsiloxane) (PTFPMS) exhibits a significantly higher resistance to biofouling compared to traditional poly(dimethylsiloxanes) (PDMS), such as Sylgard 184. The enhanced resistance is likely due to the reduction in surface energy and friction coefficients due to the incorporation of fluorine groups. Varying the fluorination content from 0 to 35 mol % trifluoropropylmethylsiloxane (TFPMS) in cross-linked PDMS exhibits consistent patterns in tribological and surface data: increased fluorination decreases friction and surface energy while increasing roughness. Profilometry reveals the formation of circular domains as fluorine groups are introduced, which increase in size with higher fluorine content. Corresponding roughness measurements show a significant rise in three dimensional (3D) root-mean-square roughness (Sq) from 0.07 ± 0.06 μm for PDMS to 1.89 ± 0.02 μm for 22.7 mol % TFPMS. Tribological data mirror the roughness trend: the friction coefficients decrease as roughness increases. Contact angle measurements for water increase from 100° to a plateau of 110°, while those for diiodomethane increase from 65° to a plateau of 90°. Contact angle hysteresis indicates that the minimum fluorination needed to impact hydrophobicity is 22.7 mol %. Lap shear tests confirm bulk adhesion of 35 mol % TFPMS to glass (0.45 ± 0.23 MPa) and to PDMS (0.10 ± 0.04 MPa). 35 mol % TFPMS exhibits 2.7 (rough) to 10 (smooth) times lower cell adhesion for E. coli and 1.7 (smooth) to 43 (rough) times lower cell adhesion for P. aeruginosa compared to PDMS. These findings highlight how a mechanistic understanding of how polymer structure and chemistry influence fouling resistance, with implications extending beyond the medical field to many industries requiring antifouling surfaces.

  PublisherDOI

• The effect of diamine structure on the thermomechanical properties of epoxy resin thermosets

  Polymer · 2025-04-16 · 3 citations

  articleSenior authorCorresponding
  PublisherDOI

• Subverting Cryptographic Hardware Used in Blockchain Consensus

  Lecture notes in computer science · 2025-01-01 · 2 citations

  book-chapterSenior author
  PublisherDOI

• Characterizing and modeling the mechanical behavior of an anion exchange membrane for carbon capture applications

  ArXiv.org · 2025-08-03

  preprintOpen accessSenior author

  A new direct air capture (DAC) technology uses a moisture swing (MS) process with anion exchange membranes, potentially offering a more energy-efficient way to remove CO2 from the air. In this MS process, the membrane absorbs CO2 as it dries and releases it when water is added. Understanding the mechanical behavior of these membranes is essential for improving the design and efficiency of DAC systems and prolonging sorbent lifetime. This study tested one anion exchange membrane, Fumasep FAA-3, under mechanical loading and various temperature and humidity conditions to measure its swelling, stiffness, strength, plastic deformation, and stress relaxation. Experimental results were used to identify a mechanical model for FAA-3 that can be used to predict the material's nonlinear viscous behavior under various loads and environments.

  PublisherOA PDFDOI

• Polymers in direct air capture: a mini review

  Polymer International · 2025-05-28 · 2 citations

  reviewOpen accessSenior author

  Abstract The urgent need to mitigate climate change has intensified interest in direct air capture (DAC) technology, which targets extracting carbon dioxide (CO 2 ) directly from the atmosphere. Among the various sorbents used in DAC, polymers have emerged as a promising solution, either as active sorbents or as structural supports for active DAC materials, due to their customizable properties, scalability and low cost. This mini‐review investigates the latest trends in polymer‐based materials for DAC and identifies critical research gaps, such as the need for thorough lifecycle assessments and in‐depth studies on the degradation of polymeric materials. It also outlines future directions, emphasizing the importance of developing cost‐effective, scalable and durable polymers that can perform efficiently across diverse climatic conditions, including the unique challenges presented by cold weather regions abundant in renewable energy. This mini‐review aims to inform ongoing efforts in the design and utilization of polymeric sorbents, providing insights that could guide the development of economically viable and environmentally sustainable DAC technologies. © 2025 The Author(s). Polymer International published by John Wiley &amp; Sons Ltd on behalf of Society of Chemical Industry.

  PublisherOA PDFDOI

• Accounting for sustainability and performance: Contrasting effects of PET-derived modifiers on asphalt durability

  Resources Conservation and Recycling · 2025-05-08 · 1 citations

  article
  PublisherDOI

• Exploring Phosphonium‐Based Anion Exchange Polymers for Moisture Swing Direct Air Capture of Carbon Dioxide

  Macromolecular Rapid Communications · 2025-03-10 · 5 citations

  articleOpen accessSenior authorCorresponding

  Abstract This study explores the performance and stability of ammonium and phosphonium‐based polymeric ionic liquids (PILs) with methyl and butyl substituents in moisture‐swing direct air capture of CO 2 . The polymers are synthesized with chloride counterions, followed by ion exchange to the bicarbonate ion, and tests for CO 2 capture capacity and stability under cyclic wet–dry conditions. The phosphonium polymer with methyl substituents [PVBT‐MeP] demonstrates the highest CO 2 capture capacity at ≈510 µmol g⁻¹, attributed to minimal steric hindrance and stronger ion pairing with bicarbonate. However, oxidative degradation is detected by 31 P NMR spectroscopy after the moisture swing experiment, with the appearance of a phosphine oxide peak at 61.28 ppm, which indicates phosphorus oxidation as the primary degradation pathway. In contrast, the ammonium polymer with butyl substituents [PVBT‐BuN] exhibits the highest stability, showing no degradation over five moisture swing cycles. Additional stability experiments in 0.5 m KHCO 3 solutions reveal no degradation for any PIL, suggesting that oxidative degradation is driven by dynamic acid‐base reactions during the moisture swing cycles in the air. These findings reveal the potential of phosphonium‐based PILs for moisture‐swing direct air capture, achieving high capacity while highlighting the need for optimized stability through counterion and structural design.

  PublisherOA PDFDOI

• Moisture-driven CO2 direct air capture and delivery for cultivating cyanobacteria

  SSRN Electronic Journal · 2025-01-01

  articleOpen access
  PublisherDOI

Recent grants

• CAREER: Towards Secure and Policy-Compliant Encrypted Communications

  NSF · $446k · 2017–2024

• SaTC: CORE: Medium: Collaborative: Theory and Practice of Cryptosystems Secure Against Subversion

  NSF · $298k · 2018–2021

• CAREER: Using electrostatic interactions to guide microstructure and mechanical properties in block polyelectrolytes

  NSF · $519k · 2019–2025

• Fouling resistant, freestanding zwitterionic polysulfones for osmotically driven membrane processes

  NSF · $311k · 2018–2023

Frequent coauthors

• Ian Miers

  University of Maryland, College Park

  24 shared

• Gabriel Kaptchuk

  23 shared

• Timothy E. Long

  Arizona State University

  19 shared

• Thomas Hellmuth

  16 shared

• Roger V. Gonzalez

  Institut des Sciences Cognitives

  16 shared

• Stephen Ayers

  University of Kansas Medical Center

  16 shared

• Paul Leiffer

  LeTourneau University

  16 shared

• Jae Sang Lee

  14 shared

Labs

• Matthew Green LabPI

Education

• Ph.D., Computer Science

  Johns Hopkins University

• M.S., Computer Science

  Johns Hopkins University

• B.S., Computer Science

  Johns Hopkins University

Awards & honors

• NSF CAREER Award (2017)
• Google Security and Privacy Research Award