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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 - PowerPoint PPT Presentation
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2005-02-22 1
KYUSHU
UNIVERSITY
SAKURAI
LABORATORY
Sakurai Lab. Kyushu University
Dr-course HER, Yong-Sork
E-voting VS. E-auction
2005-02-22 2
KYUSHU
UNIVERSITY
SAKURAI
LABORATORY
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
KYUSHU
UNIVERSITY
SAKURAI
LABORATORY
Requirements for E-voting system
Completeness : All valid votes are counted correctly, if all participants are honestRobustness : Dishonest voters, other participants or outsiders can not disturb of disrupt an electionPrivacy : 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
KYUSHU
UNIVERSITY
SAKURAI
LABORATORY
• 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
2005-02-22 5
KYUSHU
UNIVERSITY
SAKURAI
LABORATORY
Authentication
Receive IC-cardInput the IC card in voting terminal
VotingStore the contents of voter
Okayama’s e-voting
2005-02-22 6
KYUSHU
UNIVERSITY
SAKURAI
LABORATORY
Analysis of Japan‘s e-voting
ItemsThe existed voting1994 (Paper-voting)
The electronic Voting2002
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
-Councilman3 hours
4 hours 25 minutes25 minutes25 minutes
Invalid ballots-Major
-Councilman242214
00
Voting ratio 92.06 % 86.82 %
Election costs \11,630,000 \16,460,000
2005-02-22 7
KYUSHU
UNIVERSITY
SAKURAI
LABORATORY
Analysis of Japan ‘s e-voting (Cont.)
CandidateGroup
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 %
Candidate 4
Total 100%
<14,966 persons> 100 %
<1719 persons>
13.3 %
11.5 % 5.6 %
2005-02-22 8
KYUSHU
UNIVERSITY
SAKURAI
LABORATORY
E-voting ServerVoter
SSL
DB- Registration step- Voting step- Counting step
Example of E-voting system (1)
2005-02-22 9
KYUSHU
UNIVERSITY
SAKURAI
LABORATORY
Voting system(WIN95, 486-II)
Server(Linux 2.x, P-75Mhz)
Firewall(FWTK)
SSL SSL
(Stronghold, UK)
Encryption/Decryption ( PGP)
Voting program(Perl- language)
VoteCount1
The example of voting contents
(Before be transmitted)
Transmitting of encryption
The Implement of E-voting System (1)
2005-02-22 10
KYUSHU
UNIVERSITY
SAKURAI
LABORATORY
Voting center
Absentee voter
Absentee Center
①Register a
n absentee
②Send the public
-key
③Send the public-key
Bulletin Board
④Choose candidate and double encryption
⑤Send the contents of absentee
⑥Decryptand computethe voting results
⑦ Sendthe computedVoting results
⑧ Compute the voting results
⑨compare with the results of and⑦ ⑧
E-voting system for an absentee voter => Ballot-Cancellation Scheme
2005-02-22 11
KYUSHU
UNIVERSITY
SAKURAI
LABORATORY
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
KYUSHU
UNIVERSITY
SAKURAI
LABORATORY
E-auction
Bidder . . . . .
$10 $9 $11$12
Encryption Key
$ Bidding price
Recently, e-auction using Cryptographic Techniques and Network have been proposed.
A B N-1 N
2005-02-22 13
KYUSHU
UNIVERSITY
SAKURAI
LABORATORY
A first-price sealed-bid auction
A second-price sealed-bid auction
M+1st –price auctionMultiple 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.
2005-02-22 14
KYUSHU
UNIVERSITY
SAKURAI
LABORATORY
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
KYUSHU
UNIVERSITY
SAKURAI
LABORATORY
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
2005-02-22 16
KYUSHU
UNIVERSITY
SAKURAI
LABORATORY
• <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,
Related works
Scheme
[AS02] [CLK03]
WinnerLosing bidders
WinnerLosing bidders
Receipt-free scheme
No Yes Yes Yes
2005-02-22 17
KYUSHU
UNIVERSITY
SAKURAI
LABORATORY
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
2005-02-22 18
KYUSHU
UNIVERSITY
SAKURAI
LABORATORY
• 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
AA yx ,
uu yS ,
II yx ,
BB yx ,
qp,
'gpgg k mod)( '
Example of e-auction (1)
2005-02-22 19
KYUSHU
UNIVERSITY
SAKURAI
LABORATORY
Procedures 1. Registration Stage
Bidder Last -Auction issuer
Real ID
Pseudo ID Generator
Pseudo ID )( 2qiIDZP
Anonymous secret channel
Example of e-auction (1)
2005-02-22 20
KYUSHU
UNIVERSITY
SAKURAI
LABORATORY
2. Bidding stage
Bidder
Public key Iy
Random number )( 2qb Zr
bIDIbID rPxrPI ggyP 0
Bidding ID Vector
Bidder
Public key Ay
Random encryption factor 210 ),( qZkkk
)],();,[(
)],(),,[(1100
11000
kkA
kkAi gygyb
yxyxC
Bidding Vector
Last -Auction Issuer
Auctioneer
Example of e-auction (1)
2005-02-22 21
KYUSHU
UNIVERSITY
SAKURAI
LABORATORY
3. Mixing stage
1 -AI2 -AI last -AI
.
.
.
.
.
....
.
.
.
1C 2C 1nC-Group -Group -Group
Example of e-auction (1)
2005-02-22 22
KYUSHU
UNIVERSITY
SAKURAI
LABORATORY
VerifierProver
22,1 ,, qZtrkk
'222
'1211
'1
'1
'0
'0 ),,,,,,,,,(
)],(),,[(
)],)(,[(
2211
aakU
aaakT
yxyxFdcbaHS
ygF
gygy
dcba
tu
r
kkkk
),,,,( UTStr
),,,,
,,,,('1
'1
'1
'0
'1
'1
'0
'0
yxyxyg
ygxyygxyStu
r
UUTT
Compute
Accept the proof if
Designated-Verifier Re-encryption proof for Universal Re-encryption
Example of e-auction (1)
2005-02-22 23
KYUSHU
UNIVERSITY
SAKURAI
LABORATORY
VerifierProver
qZ
gbga ,),( ba
crc bvyaug ,
Compute
Accept the proof if
qZc
cCompute
IDcPr r
Proof of Knowledge of Pseudo ID
Example of e-auction (1)
2005-02-22 24
KYUSHU
UNIVERSITY
SAKURAI
LABORATORY
4. Opening Stage
AuctioneerRecover 0P
AA xkkx yxPyx )/()/('0
'0
110'1
'1
ixkk
ix byxbyx AA )/()/(
'0
'0
00'0
'0
Compute the bidding price
Bulletin Board
Example of e-auction (1)
2005-02-22 25
KYUSHU
UNIVERSITY
SAKURAI
LABORATORY
5. Trading Stage
WinnerProof of Bidding ID vector
Last -Auction issuer
Recover
Pseudo ID of the winner
Example of e-auction (1)
2005-02-22 26
KYUSHU
UNIVERSITY
SAKURAI
LABORATORY
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