Abstract. It is debatable if current direct-recording electronic voting machines can sufficiently be trusted for a use in elections. Reports about malfunctions and possible ways of manipulation abound. Voting schemes have to fulfill seemingly contradictory requirements: On one hand the election process should be verifiable to prevent electoral fraud and on the other hand each vote should be deniable to avoid coercion and vote buying. This work presents a new verifiable and coercion-free voting scheme Bingo Voting, which is based on a trusted random number generator. As a motivation for the new scheme two coercion/vote buying attacks on voting schemes are presented which show that it can be dangerous to let the voter contribute randomness to the voting scheme. A proof-of-concept implementation of the scheme shows the practicality of the scheme: all costly computations can be moved to a non time critical pre-voting phase.

Given a signature s for some message m along with a corresponding public verification key y, in a key substitution attack an attacker derives another verification key y = y-possibly along with a matching secret key-such that s is also a valid signature of m for the verification key y. Menezes and Smart have shown that with suitable parameter restrictions DSA and EC-DSA are immune to such attacks. Here, we show that in the presence of a malicious signer key substitution attacks against several signature schemes that are secure in the sense introduced by Menezes and Smart can be mounted. While for EC-DSA such an attack is feasible, other established signature schemes, including EC-KCDSA, can be shown to be secure in this sense.

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