Xavier Bultel

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Contactless communications have become omnipresent in our daily lives, from simple access cards to electronic passports. Such systems are particularly vulnerable to <i>relay attacks</i>, in which an adversary relays the messages from a prover to a verifier. Distance-bounding protocols were introduced to counter such attacks. Lately, there has been a very(More)
Ring and group signatures allow their members to anonymously sign documents in the name of the group. In ring signatures, members manage the group themselves in an ad-hoc manner while in group signatures, a manager is required. Moreover, k-times traceable group and ring signatures [1] allow anyone to publicly trace two signatures from a same user if he(More)
Akari, Takuzu, Kakuro and KenKen are logic games similar to Sudoku. In Akari, a labyrinth on a grid has to be lit by placing lanterns, respecting various constraints. In Takuzu a grid has to be filled with 0's and 1's, while respecting certain constraints. In Kakuro a grid has to be filled with numbers such that the sums per row and column match given(More)
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