This paper is a review of prior work on pointwise guessing and its application to a specific cryptanalytic attack scenario. In pointwise guessing of an unknown X, the guesser is only allowed to ask questions of the form ‘Is X equal to x?’ which we assume are answered truthfully by another agent. In a variation of this problem, the guesser first observes some side information variable Y before the guessing starts. We use these guessing games as models for a crypto system where there is a wiretapper who observes the cryptogram Y and tries to guess the plaintext message X by successively generating pointwise probes. We characterize the guessing effort in such schemes in a game-theoretic sense for the special case where the message X is a vector of independent identically distributed random variables.
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