A Security Analysis of the Helios Voting Protocol and Application to the Norwegian County Election

We present Helios, an end-to-end verifiable internet voting system. We describe the existing protocol, the encryption and decryption process with corresponding proofs, and analyse an attack against ballot secrecy. Further we do some changes to the existing voting protocol. In the original protocol we are not able to prove soundness and extract the witness in the proof of correct encryption. Hence, we are not able to make a formal proof of ballot secrecy. We solve this problem by adding a different proof of correct encryption. In the second change we combine the ElGamal encryption with a generalisation of the Paillier encryption and analyse whether it can be used as an efficient voting protocol for the Norwegian county election