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Cryptography, Puzzles, and Games Lab
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A lab that studies card-based cryptography, which realizes cryptographic techniques using playing cards and similar cards.
AboutAbout the lab
Cryptography with cards, extended to puzzles and games.
The Cryptography, Puzzles, and Games Lab mainly studies card-based cryptography, which realizes cryptographic techniques using playing cards and similar cards.
The lab collaborates with the Cryptography Theory Lab (Kunihiro Lab) at the University of Tsukuba.
Its research themes are wide-ranging, from connections to mathematics such as finite group theory and combinatorics, to applications in education, to combinations with games and puzzles.
The lab is recruiting students who are interested in any of cryptography, puzzles, games, or mathematics.
Key terms
- Card-based cryptography
- A research field that realizes cryptographic mechanisms using playing cards and shuffling, without using computers
- Secure computation
- A technology that lets each party keep its own data hidden from the others while still obtaining only the result of a computation
- Zero-knowledge proof
- A method of convincing another party that you know an answer, without revealing the answer itself
NewsLab news
Lab information session held (October 28)
Paper accepted to IEICE Transactions on Fundamentals
Student paper accepted to the international conference IWSEC 2026
Paper accepted to the international conference ICICS 2026
Paper presented at the international conference COCOON 2026
ResearchResearch themes
Building on cryptographic theory, the lab studies cryptography that uses cards (card-based cryptography) and its connections to mathematics and games. The work is mainly theoretical, addressing the limits of efficiency in secure computation and the classification of cases that can and cannot be realized.
*Illustrative imageLimits of Efficiency in Secure Computation
The main focus is secure computation. Recently the lab has been working on private simultaneous messages, a simple model of secure computation. It derives upper and lower bounds on communication cost and the number of rounds, and classifies the cases that can and cannot be realized.
*Illustrative imageSecure Computation and Proofs with Cards
This research realizes cryptographic techniques using cards. Secure computation and zero-knowledge proofs are especially active areas, and there has been major recent progress on zero-knowledge proof protocols for Sudoku.
*Illustrative imageCard-Based Cryptography and Mathematics
Problems of shuffling cards naturally give rise to cyclic decompositions of finite groups. The lab studies which finite groups have a cyclic decomposition, as well as connections to algebraic combinatorics, such as combinatorics on words.
*Illustrative imageCard-Based Cryptography and Games
The lab applies card-based cryptography techniques to games and explores new ways to play. For example, it creates virtual players for Old Maid (Babanuki), so that a game of Old Maid with many players can be played by only a few people.
MembersFaculty
The members of the Cryptography, Puzzles, and Games Lab are faculty members and master's and undergraduate students.As of 2026
- Assistant ProfessorKazumasa Shinagawa
VoicesStudent voices
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Report an errorAbout the images
The top and research theme images are illustrative and were not taken at the lab. They are cropped from Wikimedia Commons images. Cropped CC BY-SA images are provided under the same CC BY-SA license as the original (version shown on each line).
- Top image: “Playing Cards Spread” Revisorius / CC BY-SA 4.0 (cropped)
- Limits of Efficiency in Secure Computation: “Solex 99 30 padlock with keys (DSCF2659)” Trougnouf / CC BY 4.0 (cropped)
- Secure Computation and Proofs with Cards: “Riffle shuffle” Johnny Blood / CC BY-SA 2.0 (cropped)
- Card-Based Cryptography and Mathematics: “A4 Cayley graph” נוצר על ידי משתמש:עוזי ו. / CC BY-SA 3.0 (cropped)
- Card-Based Cryptography and Games: “Blackjack game 1” Scott Nazelrod / CC0 (cropped)
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