  Vote-buying and voter-coercion are the impending threats when deploying
remote online voting into large scale elections. With a policy of carrot and
stick, it will encourage voters to deviate from honest voting strategy and
spoil the democratic election. To deal with this problem, many voting protocols
proposed their solutions with the notion of receipt-freeness. However, existing
receipt-free voting protocols either rely on some impractical assumptions as
untappable communication channel, or are burden with heavy voter-side
computation and quadratic tallying complexity. In this paper, we present
$Laoco\ddot{o}n$, a brand new cryptographic voting protocol which is practical
and light-weight to be deployed in large scale online elections. By taking
advantage of proxy re-encryption, our protocol can defend vote-buying attacks.
Furthermore, we introduce a new property, candidate-adaptiveness, in electronic
voting which refers to as every candidate knows the real-time vote number
towards himself, while he knows nothing about others, nor he buys votes. We
prove the correctness of our protocol and evaluate the performance with
experimental results. Finally we advance some open problems which will be coped
in our future work.
