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Receipt-Free {K-out-of-L} Voting Based on ElGamal Encryption

Martin Hirt

We present a $K$-out-of-$L$ voting scheme, i.e., a voting scheme that allows every voter to vote for (up to) $K$ candidates from a set of $L$ candidates. The scheme is receipt-free, which means that even a malicious voter cannot prove to anybody how he voted. Furthermore, the scheme can be based on any semantically secure homomorphic encryption scheme, in particular also on the modified ElGamal encryption scheme which does not allow for efficient decryption of arbitrary large messages (but is more efficient than Paillier's encryption scheme).

We note that in contrast to the standard setting with receipts, in a receipt-free setting a $K$-out-of-$L$ voting scheme cannot be derived directly from a yes/no voting scheme.

Finally, we show that the voting protocol of Lee and Kim is not receipt-free, opposed to what is claimed in the paper.