Cryptography, Puzzles, and Games Laboratory

Welcome to the Cryptography, Puzzles, and Games Laboratory!

In collaboration with the Cryptography and Information Security Laboratory (CRISEC), we mainly conduct research on card-based cryptography. This field has been rapidly developing in recent years, covering topics from mathematical areas such as finite group theory, combinatorics, and formal verification to applications in education and entertainment, including puzzles and games. We are looking for students interested in cryptography, puzzles, and games. Why not join us and work on exciting research that may go down in the history of card-based cryptography?

🔬 Research Topics

🔐 Crypto

We focus on theory of cryptography, particularly secure computation. Recently, we have been studying private simultaneous messages. We also explore size-hiding computation and secure computation with penalties. Our interests include efficiency (e.g. communication complexity and round complexity) and classifying what is possible and impossible.

🃏 Crypto × Card

Card-based cryptography is a research field that realizes cryptographic techniques using physical cards. In this field, secure computation and zero-knowledge proofs have been studied actively. For secure computation, AND protocols have been extensively studied. For zero-knowledge proofs, there has also been a major breakthrough in zero-knowledge proof protocols for Sudoku.

🧩 Crypto × Math

In recent years, the collaboration between card-based cryptography and mathematics has been deepening. For example, problems related to card shuffling naturally lead to the concept of cyclic factorization of finite groups. The question of which groups admit a cyclic factorization is mathematically intriguing. Additionally, connections with combinatorics on words and association schemes are also being actively explored.

🎮 Crypto × Game

The fusion of card-based cryptography and games is a relatively new and unexplored research area. By applying cryptographic techniques to games, we seek to discover new ways to play and enjoy them. For example, card-based cryptography can realize virtual players in games like Old Maid, allowing small groups to simulate large-scale gameplay.

👨‍💻 Members

Kazumasa Shinagawa

Assistant Professor, University of Tsukuba

📢 News

May 28, 2025

Deepening and Exploring New Frontiers of Card-Based Cryptography through Industry-Academia Collaboration II

Kazumasa Shinagawa will give a talk at the research workshop 産学連携と数理・暗号分野連携によるカードベース暗号の深化と新境地Ⅱ organized by the Institute of Mathematics for Industry (IMI), Kyushu University. The talk title is: Open Problems on One or Two Shuffles.

May 22, 2025

New Developments in Combinatorics and Information Science

Kazumasa Shinagawa will give a talk at the research workshop New Developments in Combinatorics and Information Science organized by the Research Institute for Mathematical Sciences (RIMS), Kyoto University. The talk title is: Advances in Card-Based Zero-Knowledge Proofs for Sudoku.

May 4-8, 2025

Eurocrypt 2025

The following paper was presented at Eurocrypt 2025 held in Madrid, Spain. The presenter was Dr. Reo Eriguchi from AIST. This paper presents improved upper bounds on the communication complexity of private simultaneous messages for symmetric functions.

  • Reo Eriguchi and Kazumasa Shinagawa: Efficient Multiparty Private Simultaneous Messages for Symmetric Functions

May 01, 2025

News

Our laboratory website has been launched.

April 01, 2025

News

Kazumasa Shinagawa has joined the Institute of Systems and Information Engineering at the University of Tsukuba.

💌 Contact

Kazumasa Shinagawa

1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan

Institute of Systems and Information Engineering, University of Tsukuba

Office: Area 3, Building 3F, Room 924, Tsukuba Campus

Email: shinagawa (at) cs.tsukuba.ac.jp