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Sakurai Lab. Kyushu University Dr-course HER, Yong-Sork

E-voting VS. E-auction. Sakurai Lab. Kyushu University Dr-course HER, Yong-Sork. What is a Electronic-Voting ?. To prevent the losses by the conventional voting system Using Network and cryptography techniques Automat ic and fast voting procedure

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Sakurai Lab. Kyushu University Dr-course HER, Yong-Sork

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  1. E-voting VS. E-auction Sakurai Lab. Kyushu University Dr-course HER, Yong-Sork 2005-02-22

  2. 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…. 2005-02-22

  3. 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 2005-02-22

  4. The First E-voting in Japan • Okayama (岡山)on 23, June (2002) - Niimi(新見) : A mayoral and a municipal election • General voter • Absentee voter • Touch panel method like ATM • (Automated-teller Machine) of BANK. 2005-02-22

  5. Okayama’s e-voting Input the IC card in voting terminal Receive IC-card Authentication Voting Store the contents of voter 2005-02-22

  6. Analysis of Japan‘s e-voting Items The existed voting 1994 (Paper-voting) The electronic Voting 2002 Voting officer (43-voting place) 180-person 178-person Counting officer 85-person 58-person Admission member （入会人) 13-person 13-person • Counting time • Major • Councilman 3 hours 4 hours 25 minutes 25 minutes 25 minutes • Invalid ballots • Major • Councilman 242 214 0 0 Voting ratio 92.06 % 86.82 % \16,460,000 Election costs \11,630,000 2005-02-22

  7. Analysis of Japan ‘s e-voting(Cont.) Candidate Group The ratio of votes obtained E-voting < General voter> Existing voting <Absentee voter> Candidate 1 78.4 % 69.6 % Candidate 2 9 % 11.5 % Candidate 3 5 % 13.3 % 11.5 % 5.6 % Candidate 4 Total 100% <14,966 persons> 100 % <1719 persons> 2005-02-22

  8. Example of E-voting system (1) SSL E-voting Server Voter - Registration step - Voting step - Counting step DB 2005-02-22

  9. The Implement of E-voting System (1) Voting program (Perl- language) Encryption/Decryption ( PGP) SSL SSL (Stronghold, UK) Firewall (FWTK) Voting system (WIN95, 486-II) Server (Linux 2.x, P-75Mhz) The example of voting contents (Before be transmitted) Transmitting of encryption 2005-02-22

  10. E-voting system for an absentee voter => Ballot-Cancellation Scheme Bulletin Board Voting center ⑧ Compute the voting results ⑨compare with the results of ⑦and⑧ ①Register an absentee ⑦ Send the computed Voting results ②Send the public-key ⑤Send the contents of absentee ⑥Decrypt and compute the voting results ④Choose candidate and double encryption Absentee Center ③Send the public-key Absentee voter 2005-02-22

  11. 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 2005-02-22

  12. Encryption Key Bidding price $ E-auction • Recently, e-auction using Cryptographic Techniques and Network have been proposed. $10 $11 $9 $12 . . . . . Bidder A B N-1 N 2005-02-22

  13. Types of an E-auction • A first-price sealed-bid auction • A second-price sealed-bid auction • M+1st –price auction Multiple units of a single item are auctioned. The M highest bidders win and pay (M+1)st highest bid . . . 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. 2005-02-22

  14. 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. 2005-02-22

  15. Receipt-Free Scheme in E-auction To receive the money, a bidder should prove to coercer (or buyer) how he bided. Please, make a bid with low biding price O.K 2005-02-22

  16. Related works • <AS02> M.Abe, K.Suzuki “ Receipt-Free Sealed-Bid Auction”, ISC2002, LNCS 2002 • <CLK03> X.Chen, B.C.Lee, K.J.Kim “ Receipt-free Electronic Auction Schemes Using Homomorphic Encryption”, ICISC2003, 2005-02-22

  17. Example of e-auction (1) • Participants • 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. … We suppose that the auctioneer does not collude with last-auction issuer 2005-02-22

  18. Example of e-auction (1) • 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 2005-02-22

  19. Example of e-auction (1) • Procedures 1. Registration Stage Real ID Last -Auction issuer Bidder Pseudo ID Pseudo ID Generator Anonymous secret channel 2005-02-22

  20. Example of e-auction (1) 2. Bidding stage Bidding ID Vector Public key Random number Bidder Last -Auction Issuer Bidding Vector Public key Random encryption factor Auctioneer Bidder 2005-02-22

  21. Example of e-auction (1) 3. Mixing stage . . . . . . . . . ... last -AI 2 -AI 1 -AI -Group -Group -Group 2005-02-22

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

  23. Example of e-auction (1) Proof of Knowledge of Pseudo ID Verifier Prover Compute Compute Accept the proof if 2005-02-22

  24. Example of e-auction (1) 4. Opening Stage Auctioneer Recover Compute the bidding price Bulletin Board 2005-02-22

  25. Example of e-auction (1) 5. Trading Stage Proof of Bidding ID vector Last -Auction issuer Winner Recover Pseudo ID of the winner 2005-02-22

  26. 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 2005-02-22

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