Dr. Matthias Minihold -- Applied Cryptographer

~ Mathematics, Cryptology, and IT Security Enthusiast ~

Hello! You are curious about my studies?

I obtained my PhD 2019 during a doctorate in cryptology at Ruhr-Universität Bochum (RUB).

My main research topics were Fully Homomorphic Encryption, Lattice-based Cryptology, Deep Neural Networks, and more general Cloud Computing and Post-Quantum Crypto – primitives resistant to today’s cryptanalysis including Quantum Algorithms.

I graduated from TU Wien in mathematics, then in November 2015 became a Marie Skłodowska-Curie Research Fellow as part of the ECRYPT-NET project.

Table of Contents

Presentations

Date Topic Setting
2021-08-20 [slides] From Homomorphic Encryption to Privacy-Preserving Image Classification in the Cloud – SeminarTalk QPQ technology seminar (link…)
2021-05-11 [slides] From Homomorphic Encryption to Privacy-Preserving Image Classification in the Cloud – TechTalk Simula UiB (link…)
2021-04-07 [video, abstract] From Homomorphic Encryption to Privacy-Preserving Image Classification in the Cloud Centre for Research on Cryptography and Security@MUni (link…)
2020-04-30 [slides] Privacy-by-Design – Data Analysis with Jupyter GData Inhouse Conference (link…)
2020-02-14 [slides] Computing on Encrypted Data – GDPR-compliant data processing in the Cloud GData Inhouse Conference (link…)
2019-01-07 [slides] Fast Homomorphic Evaluation of Deep Neural Networks – FHEDiNN: Privacy-Preserving Image Classification in the Cloud IAIK @ TU Graz Crypto & Security Seminar (link…)
2018-09-20 [slides, pitch] Practical Homomorphic Encryption Integrating Advanced Cryptography with Applications Workshop (link…)
2018-07-17 Fast Homomorphic Evaluation of Deep Neural Networks: FHE–DiNN CITS@RUB Realworld Cryptanalysis Seminar (link…)
2017-10-12 [slides] Making Fully Homomorphic Encryption practical – Construction and Cryptanalysis of lattice-based schemes ECRYPT-NET School on Correct and Secure Implementation (link…)
2017-06-13 [slides] Surveillance Threatening Privacy in UK and France Ruhr-University Bochum Seminar
2017-01-22 [poster] Fully Homomorphic Encryption – Underlying Primitives ECRYPT-NET Mid-Term Review Meeting (link…)
2016-09-22 [slides] The Subset-Sum Problem – Cyptanalysis employing a Probabilistic Approach ECRYPT-NET Cloud Summer School (link…)
2016-07-14 [poster] The Subset-Sum Problem Cryptography Design for the Internet of Things (link…)
2015-09-17 [slides] Linear Codes and Applications in Cryptography RUB Oberseminar (link…)
2011-04-01 AES – Advanced Encryption Standard Wiener Algebra Seminar (link…)
2009-12-17 Multiplication of Large Integers using Fast Fourier Transform TU Wien Numerics Talk (link…)

Publications

  • Fast Homomorphic Evaluation of Deep Discretized Neural Networks (IACR-CRYPTO-2018) [link, pdf]

  • Equiprobability: Faster Algorithms for Subset-Sum Variants and Vertex Cover (AQIS-2018) [pdf]

Code

  • Practical Homomorphic Encryption. Implementations of Practical Homomorphic Encryption Schemes. [GitHub]

  • Practical Cryptanalysis. Implementation of a modified lattice attack to cryptanalyze CRT-RSA. [GitHub]

Research Interests

  • Cryptography: Fully Homomorphic Encryption (FHE)
    • [🔑] Studying FHE schemes, primitives they build upon & their hardness
    • [🔑] Defining minimal requirements for practical FHE usage, e.g., in Cloud-Computation
    • [🔑] Studying functionality limits and practicality of FHE based solutions for various use-cases

  • Cryptanalysis: Hardness, Subset-Sum Problems (SSP), Learning With Errors (LWE)

    • [🔑] Probabilistic methods to solve hardest instances
    • [🔑] Investigating algorithmic lower-bounds from a complexity theoretic perspective
    • [🔑] How many items optimally fill my knapsack?

  • IT Security: Easy to use digital privacy tools in everyday online life

    • [🔑] Deploying best practices in times of ubiquitous tracking and profiling
    • [🔑] Real-world solutions for artificial intelligence classification on encrypted images & data
    • [🔑] Discussing the impact of crypto-technology on the (unheeding?) society

Teaching @ Ruhr-University Bochum (RUB)

Apart from student project supervision, I was involved teaching the following courses, excercises and seminars:

  • [GER] Seminar über Real World Cryptanalysis { Winter 2017, Summer 2018 }

    Im ersten Teil des Seminars wird eine Serie von aktuellen wissenschaftlichen Arbeiten vorgestellt, die sich mit kryptanalytischen Angriffen auf praktisch eingesetzte Verfahren auseinandersetzen. Im zweiten Teil des Seminars folgt eine Analyse weit verbreiteter, aktuell relevanter Kryptobibliotheken und -primitiven. Hierbei soll der zugrundeliegende Quellcode abstrahiert, didaktisch aufbereitet und vorgestellt werden. Anschließend werden wir, aufbauend auf dem theoretischen Teil des Seminars, nach Möglichkeit Schwachstellen des vorgestellten Quellcodes indentifizieren.

  • [GER] Übungen zur Kryptanalyse { Summer 2016, Summer 2017, Summer 2018 } [+Moodle]

    “Kryptanalyse 1” (früher: Einführung in die asymmetrische Kryptanalyse) gibt einen Einblick in Methoden der Kryptanalyse und zeigt wie man konkrete Instanzen von Kryptosystemen theoretisch oder praktisch, unter Zuhilfenahme des Computeralgebrasystem Sage, bricht.

  • [GER] Übungen zur Kryptographie { [Winter 2016](http://www.cits.rub.de/lehre/ws1617/cryptws1617.html) } [+Moodle]

    Die Einführung in moderne Methoden der symmetrischen und asymmetrischen Kryptographie definitiert exakte Angreifermodelle um die Sicherheit der vorgestellten Verschlüsselungsalgorithmen, Hash- und Signaturverfahren unter wohldefinierten und plausiblen Komplexitätsannahmen, in diesem Angreifermodell, nachzuweisen. Die Übungen vertiefen das Verständnis, der in der Vorlesung präsentierten Theorie.

Teaching @ TU Wien

I taught several courses focussing on algebra, discrete mathematics and computer science.

Contact

You’re very welcome to send an (encrypted) E-mail: to me. Simply use my PGP-Key below or have a look at the surprisingly easy HowTo’s for Thunderbird, Webmail, M$ Outlook users to send messages, that are for my pair of eyes only – regardless whether the content is highly confidential or not. You could also use the convenient webservice to reach me.

PGP Fingerprint

Obtain the public part of the RSA key, and compare its fingerprint with your prefered encoding for verification on your device.

Key-Type Key-ID User-ID Fingerprint
GnuPG/PGP 0x5A44531D Matthias Minihold 8BF9 338E 4064 C10F C62A 5B92 CAF9 B773 5A44 531D

Scanning the key’s QR-code or comparing with its fingerprint byte sequence as according PGP Word List:

   
8BF9 338E 4064 C10F C62A 5B92 CAF9 B773 5A44 531D obtuse Waterloo chisel microwave crackdown getaway snapline atmosphere southward chambermaid erase misnomer spellbind Waterloo seabird hurricane enlist designing dwelling breakaway