News

  • Michael Reichle got a paper accepted at PKC 2024. Congratulations!
  • Dennis Hofheinz, Kristina Hostáková, Roman Langrehr, and Bogdan Ursu got a paper accepted at PKC 2024. Congratulations!
  • Dennis Hofheinz, Kristina Hostáková, Julia Kastner, Karen Klein, and Akin Ünal got a paper accepted at PKC 2024. Congratulations!
  • Roman Langrehr got a paper accepted at TCC 2023. Congratulations!
  • Sebastian Faller and Kristina Hostáková got a paper accepted at ASIACRYPT 2023. Congratulations!
  • Julia Kastner got a paper accepted at ACM CCS 2023. Congratulations!
  • Michael Klooß is visiting from 7.08.-11.08. Welcome Michael!
  • Thomas Attema is visiting from 10.07.-11.08. Welcome Thomas!
  • Adam O'Neill and Ojaswi Acharya are visiting from 30.05.-3.06. Welcome Adam and Ojaswi!
  • The Information Security lecture (co-held with the Information Security Group) was awarded the VIS Teaching Award for Best Interaction. Congratulations!
  • Sebastian Faller got a paper accepted at CRYPTO 2023. Congratulations!
  • Dennis Hofheinz, Julia Kastner, and Karen Klein got a paper accepted at CRYPTO 2023. Congratulations!
  • Akin Ünal won the Early Career Best Paper Award at EUROCRYPT 2023 with his paper "Worst-Case Subexponential Attacks on PRGs of Constant Degree or Constant Locality". Congratulations Akin!
  • Bogdan Ursu graduated with his thesis titled "New Constructions of Round-Efficient Zero-Knowledge Proofs". Congratulations Bogdan!
  • Dennis Hofheinz got a paper accepted at PKC 2023. Congratulations!
  • Dennis Hofheinz and Suvradip Chakraborty got a paper accepted at EUROCRYPT 2023. Congratulations!
  • Suvradip Chakraborty got a paper accepted at EUROCRYPT 2023. Congratulations!
  • Akin Ünal got a paper accepted at EUROCRYPT 2023. Congratulations!
  • Nicholas Brandt got a paper accepted at Financial Crypto 2023. Congratulations!
  • Michael Reichle is visiting from 12.12.-15.12. Welcome Michael!
  • Erkan Tairi is visiting from 28.11.-2.12. Welcome Erkan!
  • Christoph Striecks is visiting from 19.9.-23.9. Welcome Christoph!
  • Karen Klein got a paper accepted at ASIACRYPT 2022. Congratulations!
  • Thomas Attema is visiting from 12.9.-16.9. Welcome Thomas!
  • David Niehues is visiting from 5.9.-9.9. Welcome David!
  • Julia Kastner got a paper accepted at ASIACRYPT 2022. Congratulations!
  • Nicholas Brandt, Dennis Hofheinz, Julia Kastner, and Akin Ünal got a paper accepted at TCC 2022. Congratulations!
  • Photograph of the group in front of the CAB building

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    Motivation.

    Cryptography is a crucial tool for securing information systems. Cryptographic building blocks ensure the secrecy and integrity of information, and help to protect the privacy of users. Still, most actually deployed cryptographic schemes are not known to have any rigorously proven security guarantees. This has led to a number of far-reaching security issues in widely deployed software systems.

    Goal.

    Our goal is to provide practical cryptographic building blocks that come with rigorously proven security guarantees. These building blocks should be efficient enough for the use in large-scale modern information systems, and their security should be defined and formally analyzed in a mathematically rigorous manner.

    Technical interests.

    We are interested in the foundations of theoretical cryptography, and in general ways to derive constructions and security guarantees in a modular fashion. One research focus in our group concerns new cryptographic building blocks such as indistinguishability obfuscation, functional encryption, and fully homomorphic encryption. We are particularly interested in the design and analysis of cryptographic schemes in the public-key setting. This covers common tools like public-key encryption and digital signatures, specifically in realistic modern scenarios (such as settings with adaptive adversaries, and a huge number of users).

    Teaching

    Lecture: Digital Signatures

    This information concerns the “Digital Signatures” lecture in the Spring 2023 semester at ETH. The content for this course will be provided through Moodle.

    Lecture: Information Security

    This information concerns the “Information Security” lecture in the Spring 2023 semester at ETH. The content for this course will be provided through Moodle.

    Seminar: Current Topics in Cryptography

    You can find the link to the seminar page here.

    Available Theses

    For more details or questions in general please contact karen.klein@inf.ethz.ch.
    Survey Meta-complexity literature (Semester project only!)

    Meta-complexity is an exciting field that provides intriguing insights into how computation fundamentally works. In particular, meta-complexity techniques have established some interesting results between complexity theory and cryptography (see [1]) and seem promising in ruling out some of Impagliazzo's five worlds (see [2]).
    The goal of this project is to survey the existing literature on meta-complexity, in particular in connection to the theory of cryptography.
    A student interested in this topic should have a strong background and interest in theoretical computer science ("Theoretische Informatik" or an equivalent basic TCS course). Knowledge of cryptographic principles is beneficial but not strictly necessary.

    Nicholas Brandt
    Punctureable Signatures (Master thesis)

    A puncturable signature scheme is a special type of digital signature. It allows a signer to update their signing key sk to sk* such that certain message(s) become unsignable. This turns out to be a useful property in applications such as Proof-of-Stake based blockchains or asynchronous transaction data signing services.
    The goal of the thesis is to review existing definitions and constructions, understand their advantages and drawbacks, and propose new constructions. Depending on the interest of the candidate, this could either be interesting theoretical constructions or rather constructions with properties useful in practical applications.
    A student interested in this topic should have basic knowledge of cryptographic principles. To get yourself familiar with the topic, see for example [1] or [2].

    Kristina Hostakova
    Adaptive Security for Continuous Group Key Agreement (Master thesis)

    While (group) messaging systems with strong security guarantees are widely used in practice, these protocols either do not scale efficiently to large groups or provide significantly weaker security guarantees. The candidate construction that is currently considered by the IETF MLS working group is called TreeKEM [1]. First security guarantees for (a variant of) TreeKEM against so-called adaptive adversaries, which may choose their targets adaptively, potentially depending on information they have learned while interacting with the scheme, have been proven in [2].
    The goal of this project is to improve on these results using a proof technique that is called rewinding.
    A strong background in security reductions and probability theory is required for this project.

    Karen Klein
    Foundations of Cryptography Contact
    Universitaetstrasse 6
    CAB Building, H Floor
    8092 Zurich
    Switzerland
    claudia.guenthart@inf.ethz.ch foc.ethz.ch