1. KYUSHUUNIVERSITYKYUSHUUNIVERSITY SAKURAILABORATORYSAKURAILABORATORY 2005-02-221 Sakurai Lab. Kyushu University Dr-course HER, Yong-Sork E-voting VS. E-auction

2. KYUSHUUNIVERSITYKYUSHUUNIVERSITY SAKURAILABORATORYSAKURAILABORATORY 2005-02-222 What is a Electronic-Voting ? To prevent the losses by the conventional voting system Using Network and cryptography techniques Automatic and fast voting procedure Untill it is realized the home–voting, Convenient place-voting….

3. KYUSHUUNIVERSITYKYUSHUUNIVERSITY SAKURAILABORATORYSAKURAILABORATORY 2005-02-223 Requirements for E-voting system Completeness : All valid votes are counted correctly, if all participants are honest Robustness : Dishonest voters, other participants or outsiders can not disturb of disrupt an election Privacy : The votes are cast anonymously Unreuability : Every voter can vote only once. Eligibility : Only legitmate voters can vote Fairness : A voter casts his vote independently and is not influenced Universal Verifiability : anyone can verify a correctness of election. Receipt-freeness: A voter can not prove to a coercer, how he has voted

4. KYUSHUUNIVERSITYKYUSHUUNIVERSITY SAKURAILABORATORYSAKURAILABORATORY 2005-02-224 Okayama ( 岡山 )on 23, June (2002) - Niimi( 新見 ) : A mayoral and a municipal election Touch panel method like ATM (Automated-teller Machine) of BANK. General voter Absentee voter The First E-voting in Japan

5. KYUSHUUNIVERSITYKYUSHUUNIVERSITY SAKURAILABORATORYSAKURAILABORATORY 2005-02-225 Authentication Receive IC-card Input the IC card in voting terminal Voting Store the contents of voter Okayama’s e-voting

6. KYUSHUUNIVERSITYKYUSHUUNIVERSITY SAKURAILABORATORYSAKURAILABORATORY 2005-02-226 Analysis of Japan‘s e-voting Items The existed voting 1994 (Paper-voting) The electronic Voting 2002 Voting officer (43-voting place) 180-person178-person Counting officer85-person58-person Admission member （入会人 ) 13-person Counting time -Major -Councilman 3 hours 4 hours 25 minutes 25 minutes Invalid ballots -Major -Councilman 242 214 0000 Voting ratio92.06 %86.82 % Election costs\11,630,000 \16,460,000

7. KYUSHUUNIVERSITYKYUSHUUNIVERSITY SAKURAILABORATORYSAKURAILABORATORY 2005-02-227 Analysis of Japan ‘s e-voting (Cont.) Candidate Group The ratio of votes obtained E-voting Existing voting Candidate 178.4 %69.6 % Candidate 2 9 %11.5 % Candidate 3 5 % Candidate 4 Total 100% 100 % 13.3 % 11.5 %5.6 %

8. KYUSHUUNIVERSITYKYUSHUUNIVERSITY SAKURAILABORATORYSAKURAILABORATORY 2005-02-228 E-voting Server Voter SSL DB - Registration step - Voting step - Counting step Example of E-voting system (1)

9. KYUSHUUNIVERSITYKYUSHUUNIVERSITY SAKURAILABORATORYSAKURAILABORATORY 2005-02-229 Voting system (WIN95, 486-II) Server (Linux 2.x, P-75Mhz) Firewall (FWTK) SSL (Stronghold, UK) Encryption/Decryption ( PGP) Voting program (Perl- language) The example of voting contents (Before be transmitted) Transmitting of encryption The Implement of E-voting System (1)

10. KYUSHUUNIVERSITYKYUSHUUNIVERSITY SAKURAILABORATORYSAKURAILABORATORY 2005-02-2210 Voting center Absentee voter Absentee Center ① Register an absentee ② Send the public-key ③ Send the public-key Bulletin Board ④ Choose candidate and double encryption ⑤ Send the contents of absentee ⑥ Decrypt and compute the voting results ⑦ Send the computed Voting results ⑧ Compute the voting results ⑨ compare with the results of ⑦ and ⑧ E-voting system for an absentee voter => Ballot-Cancellation Scheme

11. KYUSHUUNIVERSITYKYUSHUUNIVERSITY SAKURAILABORATORYSAKURAILABORATORY 2005-02-2211 What is a auction ? Not a fixed Price A kind of trade for special goods In real world, a various type auctions have been enforced for decision of price

12. KYUSHUUNIVERSITYKYUSHUUNIVERSITY SAKURAILABORATORYSAKURAILABORATORY 2005-02-2212 E-auction Bidder..... $10 $9 $11 $12 Encryption Key $ Bidding price Recently, e-auction using Cryptographic Techniques and Network have been proposed. ABN-1 N

13. KYUSHUUNIVERSITYKYUSHUUNIVERSITY SAKURAILABORATORYSAKURAILABORATORY 2005-02-2213 A first-price sealed-bid auction A second-price sealed-bid auction M+1 st –price auction Multiple units of a single item are auctioned. The M highest bidders win and pay (M+1)st highest bid. Types of an E-auction The winner is the highest bidding price, he should pay his own bidding price. The winner is the highest bidding price, he should pay the second-price.

14. KYUSHUUNIVERSITYKYUSHUUNIVERSITY SAKURAILABORATORYSAKURAILABORATORY 2005-02-2214 Requirements Privacy of bid : No bid is revealed to anyone except the winner and the winning bid Proof of winner : Everyone can verify the winner and the winning price which are decided correctly Non-repudiation : The winner cannot repudiate his/her own bidding at the winning price Accountability of bidder : Any auctioneer can verify that bidders follow a protocol to cast their bids. Bid Security Nobody can forge (falsify) and tap a bid 。 Robustness Even if a bidder sends an invalid bid, the auction process is unaffected.

15. KYUSHUUNIVERSITYKYUSHUUNIVERSITY SAKURAILABORATORYSAKURAILABORATORY 2005-02-2215 O.K To receive the money, a bidder should prove to coercer (or buyer) how he bided. Please, make a bid with low biding price Receipt-Free Scheme in E-auction

16. KYUSHUUNIVERSITYKYUSHUUNIVERSITY SAKURAILABORATORYSAKURAILABORATORY 2005-02-2216 M.Abe, K.Suzuki “ Receipt-Free Sealed-Bid Auction”, ISC2002, LNCS 2002 X.Chen, B.C.Lee, K.J.Kim “ Receipt-free Electronic Auction Schemes Using Homomorphic Encryption”, ICISC2003, Related works Scheme [AS02][CLK03] Winner Losing bidders Winner Losing bidders Receipt-free scheme No Yes

17. KYUSHUUNIVERSITYKYUSHUUNIVERSITY SAKURAILABORATORYSAKURAILABORATORY 2005-02-2217 Example of e-auction (1) Auctioneer : An auctioneer decides the winning price and publishes it. Multi-Auction issuer Each auction issuer mixes the encrypted bidding price. The last auction issuer manages Pseudo ID of each bidder. Bidder : A bidder offers a bid only one time by an auction rule Bulletin Board Everyone can see the content of BB and can not erase/modify it. Participants … We suppose that the auctioneer does not collude with last-auction issuer

18. KYUSHUUNIVERSITYKYUSHUUNIVERSITY SAKURAILABORATORYSAKURAILABORATORY 2005-02-2218 Notation A secret key and a public key of an auctioneer A secret key and a public key of an auctioneer for designated verifier re-encryption proof A secret key and a public key of an auction issuer A secret key and a public key of a bidder Random numbers A generator Example of e-auction (1)

19. KYUSHUUNIVERSITYKYUSHUUNIVERSITY SAKURAILABORATORYSAKURAILABORATORY 2005-02-2219  Procedures 1. Registration Stage Bidder Last -Auction issuer Real ID Pseudo ID Generator Pseudo ID Anonymous secret channel Example of e-auction (1)

20. KYUSHUUNIVERSITYKYUSHUUNIVERSITY SAKURAILABORATORYSAKURAILABORATORY 2005-02-2220 2. Bidding stage Bidder Public key Random number Bidding ID Vector Bidder Public key Random encryption factor Bidding Vector Last -Auction Issuer Auctioneer Example of e-auction (1)

21. KYUSHUUNIVERSITYKYUSHUUNIVERSITY SAKURAILABORATORYSAKURAILABORATORY 2005-02-2221 3. Mixing stage 1 -AI 2 -AI last -AI..................... -Group Example of e-auction (1)

22. KYUSHUUNIVERSITYKYUSHUUNIVERSITY SAKURAILABORATORYSAKURAILABORATORY 2005-02-2222 Verifier Prover Compute Accept the proof if Designated-Verifier Re-encryption proof for Universal Re-encryption Example of e-auction (1)

23. KYUSHUUNIVERSITYKYUSHUUNIVERSITY SAKURAILABORATORYSAKURAILABORATORY 2005-02-2223 Verifier Prover Compute Accept the proof if Compute Proof of Knowledge of Pseudo ID Example of e-auction (1)

24. KYUSHUUNIVERSITYKYUSHUUNIVERSITY SAKURAILABORATORYSAKURAILABORATORY 2005-02-2224 4. Opening Stage Auctioneer Recover Compute the bidding price Bulletin Board Example of e-auction (1)

25. KYUSHUUNIVERSITYKYUSHUUNIVERSITY SAKURAILABORATORYSAKURAILABORATORY 2005-02-2225 5. Trading Stage Winner Proof of Bidding ID vector Last -Auction issuer Recover Pseudo ID of the winner Example of e-auction (1)

26. KYUSHUUNIVERSITYKYUSHUUNIVERSITY SAKURAILABORATORYSAKURAILABORATORY 2005-02-2226 Future works Compare E-voting system with E-auction system Extended Receipt-free Scheme for E- auction system Develop E-voting System for an absentee