Joern Schweisgut (#186)
Topic of his/her doctorate.
Elektronische Wahlen unter dem Einsatz kryptografischer Observer - Electronic Elections with Cryptographic Observers
electronic voting, election schemes, secret ballot, receipt-free, coercion-resistant
Year of completion
Long candidate lists and the possibility of vote-splitting and cross voting like in the local elections of Hesse in March 2006 strengthen the voter's position and his dimension of participation on the one hand; but they lead to a much more complex and expensive tallying. Electronic voting schemes may on the other hand reduce the expenditure of time for the tallying.
In the last years, several elections have been executed electronically, e.g. the election of the youth council in Esslingen, the works council of "Deutsche Telekom", the election of the executive board of the "Gesellschaft für Informatik".
But electronic elections do not only simplify the tallying or the voting, it also imports the risk to ease abuse and to permit large scale manipulation.
A great many of papers have been published in cryptographic literature describing how to obtain robust and verifiable election schemes.
Hirt and Sako presented the first electronic voting scheme in which voters were not able to prove their voting decision in 2000. This so-called receipt-freeness was achieved under the unrealistic assumption of an untappable channel from each authority to each voter. To solve this problem, Magkos et al. introduced an election scheme in 2001 based on a tamper-proof device, a so-called observer.
In this thesis it will be shown that the system of Magkos et al. is not receipt-free, the flaw will be fixed and the system will be improved. Then another receipt-free voting scheme with observer which combines the advantages of the Hirt and Sako scheme with the one of Magkos et al. will be presented.
Besides the long unsolved problem of receipt-freeness, there are further possibilities for an attack on electronic elections described by Juels et al. in 2005. They summed up these attacks by the notion of coercion-resistance and proposed a first coercion-resistant voting scheme.
In this thesis, an election scheme based on the usage of credentials as a proof of authorisation to vote will be introduced. In this scheme the credentials are encrypted during registration.
By using a MIX-cascade we can omit one time-consuming plaintext equivalence test from the tallying process. In addition, the observer facilitates registration and voting for the benefit of the voter. Pseudonymisation of the ciphertexts during the voting period implies a permanent secrecy of the submitted votes.
Joern.Schweisgut (at) math.uni-giessen.de