1. Cryptanalysis on Mu–Varadharajan's e-voting schemes
Source: Applied Mathematics and Computation, Vol 139, Issue 2-3, July, 2003, pp
Author: Hung-Yua Chien, Jinn-Ke Jan, Yuh-Min Tseng
Speaker: Chang-Chu Chen
Date: 10/13/2004

2. Outlines
Introduction
Review
Proposed scheme
Conclusions

3. Introduction Mu and Varadharajan claimed This paper show the failures
 Y. Mu, V. Varadharajan, Anonymous secure e-voting over a network. Proceedings of the 14th Annual Computer Security Applications Conference, CACSAC’98, 1998, pp. 293–299.
Mu and Varadharajan claimed
protect voter’s anonymity
detect double voting
authenticate the voters
This paper show the failures
the authority can easily identify the owner of a cast ballot
a valid voter or any one can vote more than once without being detected
any one can forge ballot without being authenticated

4. Structure of proposed scheme
Certificate Authority CA 1 1 1 1
Authentication Server
Ticket Counting Server AS VS
TCS 5 3
Voting Servers 4 2 Vi
Voter

5. Notations Based on RSA blind signature and ElGamal digital signature
: RSA public key
: secret key
: public key certificate issued by CA
contain Vi’s identity, public key, serial number, valid period, CA’s signature, etc.

6. Review: phase 1 anonymous ticket acquiring
Goal : AS will authenticate an eligible voter Vi and issues him an anonymous voting ticket.
Voter Vi AS
b: blind factor t: timestamp
p: large prime
verify CertVi
and
AS database

7. Review: phase 1 (cont.) anonymous ticket acquiring
Voter Vi
m: voting intention
get k2 by decrypt x3
 voting ticket

8. Review: phase 2 voting and ticket collecting
Goal :Vi can cast the voting ticket T to VS over the network. T
Voter Vi VS
TCS
get T ? ? ?
TCS database
VS database

9. Review: phase 3 tickets counting
Goal :TCS checks whether there exists a double-voting.
TCS database

10. Cryptanalysis 1
Failure of protecting voter’s anonymity
from

11. Cryptanalysis 2
Authenticated voter vote more than once without being detected
from
where
let
then

12. Cryptanalysis 3
Forging valid anonymous tickets without being authenticated
attacker choose k1,k2,r
satisfy
get
then
can pass VS and TCS

13. Conclusions Mu and Varadharajan fail protect voter’s anonymity
detect double voting
authenticate the voters