Universally Verifiable Electronic Voting Schemes With Re-encryption Mixnets
- When?
- Monday 28 March 2011, 15:00 to 16:00
- Where?
- 39BB02
- Open to:
- Staff, Students
- Speaker:
- Mr Efstathios Stathakidis
Democracy entirely depends on the elections, which must be robust and fair without cheating and electoral frauds. Voters must be sure that their vote has remained unaltered and has been correctly tallied. The election system should prevent any possible coercion and should be robust even if the official authorities are not trusted. There is a recent example where frauds and systems’ misbehaviour were reported by voters (Florida, 2000). When security properties like integrity, privacy, anonymity, confidentiality and verifiability are not supported or they have limited functionalities, attacks can be made enabling a third party to learn the voters vote. All these lead to a fundamental question: how can the voter trust the voting procedure and the announced results?
Cryptographic electronic voting systems aim to answer this question. Electronic voting systems are used in many countries. Desired properties like universal verifiability and ballot secrecy, anonymity and system’s integrity cannot be achieved using other means. In this study, we review, examine and analyse seven end - to - end verifiable voting systems along with their strengths and weaknesses. We categorise them according to the use of Mixnets for anonymity and tallying phase.
Mixnet, is a cryptographic protocol which tries to hide any correspondence between its inputs and outputs. Following a series of mix servers, votes (ciphertexts) are re-encrypted and shuffled before proceeding to the next mix server. Here, we focus on re-encryption verifiable Mixnets, based on ElGamal cryptosystem, where the correctness of the shuffling operation can be verified by any voter/party using advance zero knowledge protocols. Thanks to this property, Mixnets can be used in electronic voting systems and even when all but one mix servers are corrupt, privacy and anonymity are guaranteed. Since the assurance of correctness of the shuffling process is the most costly part during the mixing, a large portion of the literature on Mixnets is reviewed and an overview of their complexity is given. Attacks on Mixnets are presented along with their countermeasures.