Cryptographic Cryptid Protocols

Xavier Bultel, Charlène Jojon, Pascal Lafourcade

Cryptid is a board game in which the goal is to be the firstplayer to locate the cryptid, a legendary creature, on a map. Each playerknows a secret clue as to which cell on the map contains the cryptid.Players take it in turns to ask each other if the cryptid could be on agiven cell according to their clue, until one of them guesses the cryptidcell. This game is great fun, but completely loses its interest if one of theplayers cheats by answering the questions incorrectly. For example, if aplayer answers negatively on the cryptid cell, the game continues for along time until all the cells have been tested, and ends without a winner.We provide cryptographic protocols to prevent cheating in Cryptid. Themain idea is to use encryption to commit the players’ clues, enabling themto show that they are answering correctly in accordance with their clueusing zero-knowledge proofs. We give a security model which capturessoundness (a player cannot cheat) and confidentiality (the protocol doesnot leak more information than the players’ answers about their clues),and prove the security of our protocols in this model. We also analyzethe practical efficiency of our protocols, based on an implementation ofthe main algorithms in Rust. Finally, we extend our protocols to ensurethat the game designer has correctly constructed the cryptid games, i.e.,that the clues are well formed and converge on at least one cell.

Jörg Schwenk

Sho Ishibashi, Jingchen Yan, Yuichi Goto +1 more

Many cryptographic protocols have been proposed, and many studies of them have been done. However, there is no study to identify constituent elements of cryptographic protocols that are elements of the protocols consist of. The constituent elements can be used for the basis of classification of already proposed cryptographic protocols, the basis of prediction of new cryptographic protocols, and the basis of formal verification for cryptographic protocols. This paper presents primitive constituent element of cryptographic protocols that is an element so that cryptographic protocol cannot accomplish its original tasks without it.

Keith M. Martin

This chapter discusses cryptographic protocols, which provide a means for cryptographic primitives to be combined in ways that allow complex sets of security goals to be tailored to particular application environments. It describes a simple, but artificial, application in order to demonstrate that there are many different ways in which a cryptographic protocol can be designed, and also how sensitive the security of cryptographic protocols can be. It then considers the important family of AKE protocols (authentication and key establishment).

Hans Delfs, Helmut Knebl