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Privacy–Preserving Data Discovery in Distributed Health Networks with Dynamic Consent

Master Thesis

Privacy–Preserving Data Discovery in Distributed Health Networks with Dynamic Consent

Master Thesis

Abstract

Electronic health data is becoming increasingly important for clinical research and medical treatment, with more use cases emerging to improve public health. The quantity of data significantly impacts its usefulness in these applications, resulting in the necessity of sharing health data across facilities and international boundaries. However, sharing sensitive health information risks patients’ privacy due to increasing hacking incidents and data leakages. In addition, governmental regulations impede the process of organizational cooperation to build larger datasets and prohibit the reuse of existing data for evolving use cases. Recent research on dynamic consent has shown that the active involvement of patients fulfills the requirement of informed consent and positively impacts patients’ willingness to contribute their data. In this thesis, we adopt state-of-the-art techniques to develop a new distributed health data network for data discovery with dynamic consent that builds upon result aggregation rather than data aggregation to eliminate the need to share patients’ health data. The evaluation of our test system shows that we can scale the network to hundreds of institutions and process datasets with more than ten million records within thirty seconds.

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Acknowledgements

Prof. Dr.-Ing. Klaus Wehrle

for allowing me to work on this thesis.
Priv.-Doz. Dr. rer. nat. Walter Unger

all his compelling lectures have ignited my passion for computer science and motivated me to persevere in my studies. His lectures have significantly enriched my academic perspective.
Johannes Lohmöller, M. Sc.

for supporting me throughout the thesis with his expertise, advice, and guidance, even during times of high workload. His continuous feedback and criticism helped me to improve my thesis throughout my work.
The entire team at COMSYS

for all the constructive feedback I received while writing this thesis has greatly enhanced my work. Moreover, I want to thank the entire chair for the long-lasting access to a dedicated server for evaluation purposes. Without this access, the results of my thesis would not have been possible.

Languages

Rust

Python

Bash

Tools

libp2p

tokio

mininet

onos

Docker

GitLab

LaTeX

Integer Program Solving Call TreeReversal

Bachelor Thesis

Integer Program Solving Call TreeReversal

Bachelor Thesis

Abstract

The call tree reversal is an algorithmic solution to reverse the data flow of program execution with limited available memory using argument checkpointing. Call tree reversal is proven to be NP-complete and, hence, finding a good solution in a reasonable time is unlikely. Established heuristics exist for this problem, but they lack the potential for customization. In addition, they do not consider the possibility of result checkpointing which is an extension to the standard call tree reversal problem. This thesis introduces an IP formulation solving call tree reversal to challenge those issues. Furthermore, this formulation is extended to support result checkpointing and serves as a foundation for further analysis comparing solutions for call tree reversal with and without result checkpointing.

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Acknowledgements

Prof. Dr. Uwe Naumann

for offering the bachelor thesis, giving a great introduction to the topic, and continuously providing helpful material
Dr. Johannes Lotz

for his supervision, he helped me lay out my milestones, monitored my progress, and always found time and good advice for any issue on the way

Tools

Vagrant

CMake

CMPL

MySQL

MATLAB

Languages

C++

Javascript

PowerShell

LaTeX

Microsoft's C++ Standard Library Contribution

Open Source Contribution

Microsoft's C++ Standard Library Contribution

Open Source Contribution

During my semester break, I took some time to contribute to Microsoft’s C++ standard template library implementation. My goal was to familiarize myself with elaborated open-source project management led by industry-leading companies.

I managed to get two out of three pull requests merged and released. Those included a bug fix and an optimization of the build system for internal dependencies on boost, which induced a circular binary dependency on the STL. Furthermore, the change dropped the requirement of a package manager in favor of a patched git submodule. I adopted these changes into the continuous integration pipeline using GitHub actions.

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Acknowledgements

Stephan T. Lavavej

for reviewing my changes, pushing required changes to boost math, and his welcoming attitude to the community
Alex Guteniev

for reviewing my changes, and continuously giving feedback
Avatar Curtis J Bezault

for benchmarking my changes on hardware, I had no access to

Tools

GitHub

GitHub Actions

Git

CMake

Languages

C++

L1 Blockchain Engineering

Blockchain

L1 Blockchain Engineering

Blockchain

During the blockchain revolution, I recognized a fragmented landscape where numerous Cryptonote forks were being developed in silos. Each fork had its own set of developers working on unique improvements, leading to a scattered ecosystem. This observation led me to conceptualize the Galaxia Project.

Problem

The blockchain community, particularly those working on Cryptonote forks, encountered challenges. While individual forks saw advancements, these improvements were often confined to their specific chains. As a result, many developers were reinventing the wheel, working on similar enhancements across different forks, leading to duplicated efforts and a need for more standardization. Solution By centralizing these improvements, the Galaxia Project was born out of the need to consolidate these scattered efforts. I envisioned it as both a framework and an educational blockchain. The project was meticulously designed to serve as a repository of state-of-the-art technologies and improvements. It delivered multiple libraries, making it easier for other Cryptonote forks to adopt the latest advancements. Further, different technologies could be enabled and configured using a simple configuration file, enabling easier deployment of new forks and test environments.

Result

The impact of the Galaxia Project was evident in its widespread adoption. Over 200 nodes actively ran the Galaxia main chain, complemented by more than 20 dedicated test and staging network nodes. The influence of the project, however, extended beyond its own chain. The development efforts bore fruit in the form of reusable components that found their way into other Cryptonote forks, enhancing their capabilities and robustness. Moreover, in the process of modernizing the Cryptonote source code, several security issues were unearthed and promptly addressed, fortifying the integrity of the entire ecosystem. Besides improvements of the bandwidth, latency, and security of network protocols, I also managed to port some features of greater improvements into reusable components. Most notably are bulletproofs, pruning, and an improved asynchronous runtime utilizing fibers.

Challenges

Managing the Galaxia Project presented several complexities. Overseeing a large open-source community required effective communication and clear direction. The project’s weekly release cycle necessitated rigorous processes for testing, staging, and production environments. Additionally, the profound exploration into blockchain technology brought forward challenges related to understanding and applying cryptographic principles, which prompted my decision to switch my master’s majors to cryptography and IT security.

Conclusion

Throughout the evolution of the Galaxia Project, I not only honed my skills in managing open-source communities and debugging complex distributed environments but also built a profound understanding of the intricate inner workings of blockchains and their interrelations. My foray into this domain further enriched my knowledge of network programming. Working under tight timelines, I sincerely appreciate the vibrant community and the myriad of dedicated individuals who played pivotal roles in the project’s success. It is a source of immense satisfaction to recognize that my endeavors have added value to multiple chains within the blockchain ecosystem.

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Acknowledgements

jerme404

for developing the block explorer and providing computation power for testing
MaddestHatter

for actively testing changes and helping out the community with any question
angrywasp

for reviewing critical code changes in the cryptography and consensus machinery, as well as promoting our community

Languages

C++

Python

TypeScript

Bash

PowerShell

Tools

Docker

GitLab CI/D

RocksDB

vue.js

MkDocs

CMake

Breakpad

.NET

boost

An Overview To The Excluded Grid Theorem

Algorithmic Graph Theory

An Overview To The Excluded Grid Theorem

Algorithmic Graph Theory

Abstract

This paper summarizes the proceeding of Robertson and Seymour’s so-called Excluded Grid Theorem. It states the existence of a bound of treewidth for a graph not to contain a grid of specified size as a minor. While recent research on this topic has improved far forward, we focus on a recent paper from Julia Chuzhoy showing a new, improved, and simplified proof, working out essential concepts and techniques used by her and other referenced publications.

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Acknowledgements

Dr. rer. nat. Martin Grohe

for offering a great selection of graph theory topics, reviewing my paper, and giving feedback on my presentation
Dr. Konstantinos Stavropoulos

for helping me with any questions regarding my topic and providing additional material

PoW Algorithm Optimizations

Blockchain

PoW Algorithm Optimizations

Blockchain

For a consensus algorithm based on proof-of-work, the threat of an optimized closed-source miner is non-negligible, especially if it comes to altered or new hash algorithms that claim to be ASIC or GPU resistant.

As part of my community work on CryptoNote-based forks, I helped optimize the existing implementation, fix an exploit of the hash algorithm, and provide a proof of concept implementation using OpenCL.

As a result, all miners had access to the faster implementation, and the exploit got fixed, providing more security to potential 50 percent attacks.

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Acknowledgements

angrywasp

for his welcoming attitude to the community, reviewing my changes, and helping me to explore the monero source code basis

Languages

C++

OpenCL

Network Improvements and Secuirity Fixes

Blockchain

Network Improvements and Secuirity Fixes

Blockchain

Turtlecoin is a privacy-focused and developer-friendly fork of CryptoNote. Thanks to their open-minded community and excellent support, I adapted quickly to their codebase.

I discovered and fixed bugs in their network protocol, database implementation, and block verification, helping them secure and strengthen their cryptocurrency implementation.

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Acknowledgements

Brandon Lehmann

for reviewing and approving my changes, as well as for our helpful endless discussions on consensus algorithms
zpalmtree

for reviewing and approving my changes
Turtlecoin Community

for their welcoming and friendly attitude, helping me out with technical questions, and generally having a great time

Tools

RocksDB

Docker

GitHub

Langauges

C++

WMS Data Extraction

Geo-Information Service

WMS Data Extraction

Geo-Information Service

Besides my study and work, I got offered to develop an application for GIS data extraction from image layers using a WMS service.

Problem

At a real estate valuation company, a working group copied standard ground zones and corresponding values by hand from a WMS service using Qgis. This time-consuming and expensive process dealt with error rates and quality assurance of imported data.

Due to a large amount of data and long processing time, the working group could not ensure recently updated data or import additional data sources.

Solution

The entire process got analyzed and mapped to a data pipeline. Next, every step got automated and parameterized for future customization, featuring new data sources. Finally, the application got reviewed, trained, and deployed.

Result

The company could speed up importing new data significantly from several months to about a day using the application. Furthermore, the resulting quality increased, and the process got far less error-prone. As a result, it was possible to import additional data sources and update them as soon as new versions got released.

Challenges

The different capabilities of WMS services and the variety of data representation put significant challenges to the design of data import. Furthermore, scanning the entire area at the most granularity was infeasible and inefficient. Therefore, a hierarchical map analysis put new challenges to the parallelization.

Furthermore, the combination of applied computational geometry and image recognition in geo-information systems put some exciting obstacles to the reusability of algorithms with different data representations.

Tools

Qgis

OSM

OpenCV

CMake

Languages

C++

Lua

Das Graph Genus Problem ist NP-Vollständig

Complexity Theory

Das Graph Genus Problem ist NP-Vollständig

Complexity Theory

Abstract

In the Proofs of NP-completeness seminar at the Chair i1 Complexity and Algorithms of RWTH Aachen University, I was assigned the proof of NP-completeness of the Graph Genus Problem. This summary of the proof given by C. Thomassen elaborates on the mathematical structures and foundations used and the insights gained in the proof.

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Acknowledgements

Prof. Dr. Ir. Gerhard Woeginger

for offering a great selection of np-completeness topics, reviewing my paper, and giving feedback on my presentation

Parallel Design Patterns

Parallel Programming

Parallel Design Patterns

Parallel Programming

Abstract

While multicore architectures get more distributed in modern computers, taking advantage of them becomes more critical. This paper introduces design patterns integrating structured concurrency into current software. Therefore environment and suitable practices get categorized. Further several patterns get presented with a focus on their underlying domain. Following these patterns, get compared against each other and in combination for different application cases.

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Acknowledgements

Zia Ui Huda

for supervision and giving helpful feedback on the way

Srsly Wicked Pinball

Computer Graphics

Srsly Wicked Pinball

Computer Graphics

In this practical course, a pinball game was to be developed with a focus on the graphics and technical detail rather than the gameplay. We implemented a variety of modern 3D effects and used the Bullet engine for complex rigid body physics. The pinball table is stored in a huge XML-file that contains the composition and material configuration of all 3D object as well as Lua-scripts that are responsible for a majority of gameplay elements.

Our game is set in a futuristic and surreal world consisting of metallic and crystal-like materials. Mysterious energies power the pinball table as well as a maelstrom of background objects.

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Acknowledgements

Prof. Dr. Leif Kobbelt

for allowing participating in the development of a game and providing the ACGL framework
Dr. Jan Möbius

for supervision and always having time to have a look at issues on the way as well as hinting solutions
Philip Trettner, Philipp Bartels, Theo Dreßen, Mateusz Buglowski

for the great teamwork and relaxed environment even in times of high workload

Tools

OpenGL

Bullet Engine

CMake

Languages

C++

Lua

XML

iOS App Development

Game Programming

iOS App Development

Game Programming

Crazy Olfo was an app developed by two fellow students and me. It was an arcade spin-off of the flash game Dolphin-Olympics.

While the app did not result in the success one may hope for, I gladly recognize and enjoy the impact of knowledge and experience gained. Not only did I get my hands on a lot of new tools, frameworks, and an operating system, but I also managed to plan, execute and finish a project with my fellow students.

Up to today, the new programming language, framework designs, and project management techniques I have learned push me to come up with better solutions from a broader range of knowledge and inspiration.

Acknowledgements

Raoul Schaffranek

Tools

Xcode

Cocos

App Store

CS6

Langauges

Objective-C

opengl-es