1. A Practical Voting Scheme Using One Server with a Secure Coprocessor
Date：
Reporter: Chien-Wen Huang
出處:ICIC Express Letters Volume 3, Number 3, September 2009

2. Outline Introduction Conclusions The Requirements of E-Voting System1
The Requirements of E-Voting System 2
An Innovative Practical E-Voting Scheme 3
The Analysis of the Proposed Scheme 4
Conclusions 3 5

3. Introduction
Voting is common in our daily life, from electing the president to selecting committees of certain organizations .
PIR: which hides the real purpose of inquiry of the user by querying K servers.
Smith et al. used a secure coprocessor (SC) in their PIR solution.
SC: is a temper-proof device with small memory; it is designed to prevent anybody from accessing its memory.

5. The Requirements of E-Voting System
Eligibility: Only eligible voters are permitted to cast their ballots.
Privacy: There is no association between voter’s identification and a marked ballot.
Uniqueness: No voter can cast his ballot more than once.
Completeness: A voter’s ballot cannot be altered, and all valid ballots are counted correctly.
Fairness: No one can affect the result of voting.

6. Verifiability: Voters can verify that their ballots are counted correctly.
Robustness: A voting scheme will be successful regardless of partial failure due to a malicious voter.
Uncoercibility: Bribery is prevented because no voter can prove to others what he or she voted.
Efficiency: The computations can be performed efficiently.
Mobility

7. An Innovative Practical E-Voting Scheme

8. tamper-proof device:the information can not be detected or distorted by the server or anyone else.
Database 1 stores the roster,identification(ID) and personal information of all voters.
Database 2 stores the encrypted voter’s identification(ID'),a marked ballot (vote'), and the encrypted voting information (C).

9. -PKSC: the public key of SC -SKSC: the secret key of SC
the following notations are used in the description
-PKSC: the public key of SC
-SKSC: the secret key of SC
-PKV: the public key of the voter
-SKV: the secret key of the voter
-ID: the voter’s identification
-ID':the encrypted voter’s identification (by hash function)
-ST:the temporal storage for gotten ballot identification stored by secure coprocessor

10. -Vote: the blank ballot -Vote': the marked ballot (voted by the voter) -M: the secret message of voter’s identification information -M': the secret message of voter’s identification created by SC -C: the secret message of voting created by voters -S: the secret message of unverified ballot created by voter

11. -S': the verified message of ballot created by SC -E: the error message of verified ballot created by SC

12. Authentication Phase
SignV=ESKv(ID)
SignSC驗證正確表示已收到

13. Voting Phase
Then, it verifies SignV ; if it is correct, it saves ID' and C of the voter into Database 2

14. Announcement Phase
Step8:Decrypted ID’ in C is compared to the identification ID’ (之前HASH的部分)

15. Verification Phase
All eligible voters can get their own (ID', C)from bulletin board system.
If the person is the qualified voter and C is the same as in Database 2,then decrypt C.
C=ID’,SignV,Vote’
Compare SignV,Vote’

16. The Analysis of the Proposed Scheme
Eligibility: SC verifies the voter’s identification ID.
Privacy:The voter’s identification ID' and voted ballot Vote' are encrypted by the public key PKSC of SC.
Uniqueness: Because the voter’s ID is verified by SC, anyone will not be able to transmit repeated identification (ID) to vote twice.

17. Completeness: Although the voters’ ballots are stored in Database 2,C=(Vote', ID',SignV )are encrypted by PKSC .
Fairness: Any illegal voter cannot pass the roster’s authentication procedure by SC (he cannot forge SignV of a legal voter.)
Verifiability: When SC acquires S, it can decrypt S to obtain Vote', SignV, ID' and C.
Robustness: voter’s ID is verified by SC and no one can know any eligible voter’s voting information.

18. Uncoercibility: all voters can acquire their own (ID', C) from bulletin board system and their ballots are verified by SC.
Efficiency: This e-voting scheme is suitable for small-scale area; it can run smoothly in present server performance and internet environment.
Mobility: The voters can vote through the proposed e-voting scheme at any place where they have access to the internet.

19. Conclusions
An innovative and practical e-voting scheme is presented for small-scale elections
The scheme can protect voters’ personal privacy and offer secure processes throughout every phrase of an election.
The voting scheme has practical value because of its low cost, high efficiency, and strong security

20. Thank You !