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I'm looking into coercion-resistant voting schemes and one of the key elements of coercion-resistance is resistance to randomization attacks.

Juels et al. define a randomization attack as one where adversary coerces the voter to vote for a random candidate (as drawn from some distribution). Many other articles have since repeated this as a requirement for coercion-resistant voting schemes, so it seems to be important.

Since coercion-resistance is an extension of receipt-freeness, and receipt-freeness already guarantees that a voter can't be coerced to vote for a particular candidate, I'm having a lot of difficulty imagining a scenario where both of the following properties hold:

  1. Adversary is unable to force a voter to vote for a particular candidate
  2. Adversary is able to force a voter to vote for a random candidate

Can you provide an example of such a scenario?

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Hirt and Sako present such a scenario here. Informal description:

A group of mutually distrusting authorities have encrypted candidates and shuffled their order. The voter expresses their choice by publicly pointing to an encrypted candidate. Outsiders can not tell who the encrypted candidate is, but the voter knows because each authority has secretly told the voter how they shuffled. Because the authorities use a designated verifier proof to convince the voter, only the voter is convinved. If the voter would attempt to pass the proof to the adversary, they would not be convinced, because the proof is constructed in such a way that the voter could have forged it.

  1. The adversary is unable to force a voter to vote for a particular candidate, because the voter is unable to prove to the adversary, which choice (in the encrypted and shuffled list of candidates) corresponds to which real life candidate.

  2. The adversary is able to force a voter to vote for a random candidate, because they can randomly pick a choice in the encrypted and shuffled list and verify that the voter indeed votes for the choice that they picked.

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