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Abstract. Recently, multiple cryptographic schemes for data collection with self-enforcing privacy were proposed by Golle et al. The schemes allow participants of electronic polls to prove a pollster's guilt if he distributes responses. Introducing punitive damages for such misbehaviour creates incentives for a pollster to protect the respondents' privacy. To achieve fairness, a proof must be feasible if and only if a pollster indeed leaked information. This paper analyses the scheme proposed for self-enforcing privacy with no release of data. Neither parameter publication nor cooperative indictment have been defined up to now. We show that both are of key importance to ensure fairness and describe potential attacks of a malicious pollster. After a detailed analysis, we propose two extensions preventing such actions. In addition, a possibility for the pollster to gain an unfair advantage in the basic scheme is identified and according checks put forward.