Theory and Foundations News
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Information Asymmetry and Cryptography
In a recent work, visiting undergraduate student Yahel Manor and Warwick DCS researchers Jinqiao Hu and Igor Oliveira addressed a fundamental question relevant to the security of cryptographic protocols.
The symmetry of information principle says that the amount of information that a sequence x of bits reveals about another sequence y is essentially the same in either direction. This is known to hold in an idealised world where computations can take an arbitrarily long time, as demonstrated by A. Kolmogorov and L. Levin in the 1970s. In contrast, modern cryptography is built around deliberate asymmetry—for example, functions of the form y = f(x) that are easy to compute but hard to invert (one-way functions).
The new work shows that, once one moves from the idealised setting of time-unbounded computations to the more realistic world of efficient, randomised computations (algorithms that must run quickly and may use randomness), this symmetry can fail in a strong and unconditional way. In other words, computational constraints can yield information asymmetry. In practical terms, this supports the intuition that information may not be extracted efficiently: knowing y = f(x) may not make x efficiently recoverable to the extent that an (ineffective) symmetry principle would suggest, even when x and y are closely related.
Earlier work formally tied an average-case form of this symmetry failure to the existence of one-way functions, the central primitive in cryptography. By proving new failures of symmetry of information, the authors provide concrete progress towards the computational asymmetry that underpins encryption, digital signatures, and many other cryptographic protocols.
This work will be presented at the 58th Annual ACM Symposium on Theory of Computing (STOC) in June 2026 in Salt Lake City, Utah, USA.
Failure of Symmetry of Information for Randomised Computations
Jinqiao Hu (University of Warwick); Yahel Manor (University of Haifa); Igor C. Oliveira (University of Warwick)
The paper describing this research is available here.
Martin Costa successfully defends his PhD thesis
Many congratulations to Martin Costa for passing his PhD viva, with Prof Long Tran-Thanh (Warwick) and Dr Christian Konrad (Bristol) as examiners. Martin has worked on two different fundamental topics in algorithms - clustering and edge coloring. His work on clustering led to a Google PhD fellowship, and his work on edge coloring (the topic of his thesis) led to a best paper award at STOC. During his PhD spanning 3 years, Martin published 7 papers in STOC/FOCS/SODA, 2 papers in ICML/NeurIPS, and 1 paper in ICALP. We wish him all the very best for the next stage of his career.
Workshop Algorithms & Complexity @ Warwick
The workshop Algorithms & Complexity @ Warwick took place at the University of Warwick on September 22-23, 2025 (see https://sites.google.com/view/algorithmscomplexitywarwick2/home for more details).
The aim of the event was to highlight several recent exciting advances in the field of Algorithms and Complexity, to facilitate interactions within the research community, and to provide an excellent opportunity for Theory researchers (including academics, postdocs, and students) to connect and collaborate.
We had a fantastic list of invited speakers by renowned world experts: Albert Atserias (Technical University of Catalonia), Raheleh Jalali (University of Bath), Sanjeev Khanna (University of Pennsylvania), Tomasz Kociumaka (Max Planck Institute for Informatics), Michal Koucký (Charles University in Prague), Or Meir (University of Sheffield and University of Haifa), Rahul Santhanam (University of Oxford), Thomas Sauerwald (University of Cambridge), Roei Tell (University of Toronto).