I' Electronic voting system

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E-voting VS. E-auction
Sakurai Lab. Kyushu University Dr-course HER,
Yong-Sork
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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 homevoting, Convenient
  place-voting.

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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-freenes
s A voter can not prove to a coercer, how he
has voted
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The First E-voting in Japan

• Okayama (??)on 23, June (2002)
• - Niimi(??) A mayoral and a municipal
  election

• General voter
• Absentee voter

• Touch panel method like ATM
• (Automated-teller Machine) of BANK.

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Okayamas e-voting
Input the IC card in voting terminal
Receive IC-card
Authentication
Voting
Store the contents of voter
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Analysis of Japans 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 (???)
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
Election costs
\11,630,000
\16,460,000
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Analysis of Japan s e-voting (Cont.)
Candidate Group
The ratio of votes obtained
E-voting lt General votergt
Existing voting ltAbsentee votergt
Candidate 1
78.4
69.6
Candidate 2
9
11.5
Candidate 3
5
13.3
11.5
5.6
Candidate 4
Total
100 lt14,966 personsgt
100 lt1719 personsgt
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Example of E-voting system (1)
SSL
E-voting Server
Voter
- Registration step - Voting step - Counting step
DB
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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
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E-voting system for an absentee voter gt
Ballot-Cancellation Scheme
Voting center
? Compute the voting results
?compare with the results of ?and?
?Register an absentee
? Send the computed Voting results
?Send the public-key
?Send the contents of absentee
?Decrypt and compute the voting results
?Choose candidate and double encryption
Absentee Center
?Send the public-key
Absentee voter
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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

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E-auction

• Recently, e-auction using Cryptographic
  Techniques and Network have been proposed.

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11
9
12
. . . . .
Bidder
A
B
N-1
N
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Types of an E-auction

• A first-price sealed-bid auction
• A second-price sealed-bid auction
• M1st price auction
• Multiple units of a single item are auctioned.
  The M highest bidders win and pay
• (M1)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.
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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.

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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
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Related works

• ltAS02gt M.Abe, K.Suzuki Receipt-Free Sealed-Bid
  Auction, ISC2002, LNCS 2002
• ltCLK03gt X.Chen, B.C.Lee, K.J.Kim Receipt-free
  Electronic Auction Schemes Using Homomorphic
  Encryption, ICISC2003,

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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
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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
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Example of e-auction (1)

• Procedures

1. Registration Stage
Real ID
Last -Auction issuer
Bidder
Pseudo ID
Pseudo ID Generator
Anonymous secret channel
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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
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Example of e-auction (1)
3. Mixing stage
. . .
. . .
. . .
...
last -AI
2 -AI
1 -AI
-Group
-Group
-Group
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Example of e-auction (1)
Designated-Verifier Re-encryption proof for
Universal Re-encryption
Prover
Verifier
Compute
Accept the proof if
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Example of e-auction (1)
Proof of Knowledge of Pseudo ID
Verifier
Prover
Compute
Compute
Accept the proof if
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Example of e-auction (1)
4. Opening Stage
Auctioneer
Recover
Compute the bidding price
Bulletin Board
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Example of e-auction (1)
5. Trading Stage
Proof of Bidding ID vector
Last -Auction issuer
Winner
Recover
Pseudo ID of the winner
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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