Secure Electronic Voting System

1
Secure Electronic Voting System

• SD 1103
• Semester 2 Presentation
• Adam Diemert
• Akshay Raj
• Yu Chen
• Advisor Dr. Katti

2
Introduction

• The electronic voting system provides a secure,
  easy way to vote between two options. This can
  be used for voting for or against legislative
  bills or for deciding between two candidates.
• The difficulty is providing a secure system that
  allows for voters to maintain privacy.
• The security comes from encryption, and the
  privacy comes from the method used to encrypt and
  decrypt the votes.

3
Requirements-Hardware

• We were given basic hardware requirements for the
  project.
• The voter has to be able to vote on one module.
• The vote will be counted on another module.

4
Requirements

• The vote needs to be public and verifiable.
• The results will be displayed on the bulletin
  board and digital signatures will be displayed to
  ensure authorization.
• The El Gamal encryption scheme will be used.
• The votes will be counted without being
  individually decrypted for privacy.
• The encryption will use small numbers, and if
  time allows, large numbers will be attempted.

5
Transceiver

• We need a transceiver to send messages from one
  breadboardd to another breadboard, store it, and
  send signal back to the first breadboard. We
  choose the MRF49XA transceiver from Microchip.
• low-cost-2.82
• two-way, short range wireless applications
• can be used in the 433, 868, and 915 MHz
  frequency bands

6
Pin Diagram Transceiver
7
MICROCONTROLLER TO MRF49XA INTERFACE
8
APPLICATION CIRCUIT
9
Very small chip
10
16-Lead Plastic Thin Shrink Small Outline (ST)
4.4 mm Body TSSOP
11
Problems

• Because the chip is surface mount, we cannot put
  it in our breadboard. We needed to find a way to
  use it in our breadboard. We found some options.

Two methods to problems

• 1. just order a breakout board built on
  digi-key.com from Jeff.
• 2.we build a breakout board by ourselves.

12
Our first option

• Thinking about the price and convenience, we
  decide to build the adaptor by ourselves.

13
Top of the board
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Back of the board
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Front of the board
16
Problems again

• Other parts are all very small, even smaller than
  chip itself. For example, capacitors and
  inductors with small values. It is almost
  impossible to solder them to our final PCB if we
  want to do it by ourselves.

Solution

• We had to choose the other way we mentioned
  before, which is that we directly order a
  breakout board that every components were
  soldered. Then we found MRF49XA PICtail/PICtail
  Plus Daughter Board

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MRF49XA PICtail/PICtail Plus Daughter Board
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RF Transceiver daughter board
Wire Antenna
Power Disconnect/ Current Measurement Headers
24AA02E48 EUI Node Identity Serial EEPROM
MRF49XA Sub-GHz Transceiver
PICtail and PICtail Plus Connectors
19
Datasheet of MRF49XA PICtail/PICtail Plus
Daughter Board
20
Components used in Hardware

• Two LCDs of 16X4 characters.
• Two 3X4 Keypads
• Two Microcontroller (18F4620)
• Crystal oscillators 20 MHz

21
Design Module

• Voting Panel

• Bulletin Board

22
Circuit Diagram for LCD and Keypad Interface
23
Pin Diagram for RF board
24
Circuit schematic on multisim
25
PCB Layout
26
Software

• The software has several routines that are used
  for the encryption.
• The vote counting code is to be put on one of the
  modules.
• The voting code is to be put on the other module.
• There are supporting routines that do things such
  as
• Retrieve entries from the keypad
• LCD and transceiver drivers
• Calculations such as finding numbers that will
  work in the encryption

27
Voting Code

• The voting code works in this order
• Calculate the correct x for the encryption
  (discussed later)
• Ask user to input the vote and one other number
  for the encryption
• Calculate encryption numbers r and t
• Send r and t to the other module
• Wait for a response confirming reception of vote
• Ask whether more voters are waiting to vote
• Repeat process if there are more voters

28
Voting Counting Code

• This code works as follows
• Calculate x for encryption as in the other
  routine
• Receive r and t from other module
• Multiply r and t by other votes previously
  captured
• See if there are more votes (variable set while
  receiving r. If r ends up being re, then
  there are no more votes.
• Calculate decryption of product of votes
• Calculate the number of votes that correspond to
  the number from decryption
• Set variables and output results to the users

29
El Gamal Basics

• Choose p, which is a prime number
• Choose g, which is an integer
• Choose x, which in our case is chosen using the
  Extended Euclidean Algorithm
• Calculate h, which is gx mod p
• User choose vote and k, a random encryption
  number
• Encrypt rgk mod p, thkgvote mod p
• Vote can be either 1 for yes or -1 for no.

30
El Gamal Basics

• When all the votes are collected, multiply rs
  and ts.
• r1r2r3rn, t1t2t3tn
• This gives a sum of votes in the exponent because
  multiplying like bases causes an addition in
  exponents.
• Decrypt this product of votes to receive M, which
  is g(net number of votes)

31
Extended Euclidean Algorithm

• The Extended Euclidean Algorithm is used to
  calculate an acceptable value of x.
• This is needed because El Gamal encryption uses g
  and g inverse, but needs to use only integer
  numbers.
• If we choose g6, then mathematically, g
  inverse1/6. The Extended Euclidean Algorithm
  calculates an acceptable integer inverse of g.
  The integer is the inverse for the encryption.
• The algorithm gives g inverse3, if we choose
  g6.

32
Extended Euclidean Algorithm-MATLAB

• function xexteucalg(x,y)
• a0x xg
• b0y yp for el gamal
• t00
• t1
• s01
• s0
• rmod(a0,b0) ra0-qb0 is the remainder
• q(a0-r)/b0 need only result with no
  remainder
• while rgt0
• tempt0-qt
• t0t
• ttemp
• temps0-qs
• s0s
• stemp
• a0b0
• b0r
• rmod(a0,b0) ra0-qb0 is the
  remainder

33
Decryption

• We decrypt the product of votes to get g(net
  number of votes) as described above.
• If our answer comes out as x, or g-1, we have to
  compare to see if that is a correct answer. This
  can be checked. x1 mod p corresponds to one no
  vote.
• If x3, and the result comes out as 3, we know
  there was a net of one no vote because p is
  always larger than x.
• If we get 10 from the decryption, we check with
  x3 mod p. x3, so x327, mod p10. We know this
  corresponds to 3 no votes.

34
Testing and Evaluation-Software

• I tested my code by running the algorithms in
  MATLAB.
• I found many errors this way, and I discovered
  that the encryption and decryption do not work if
  integers are not used, prompting questions that
  led to the Extended Euclidean Algorithm.
• There were some problems with this method of
  testing.
• MATLAB rounds to 15 significant digits, which
  really limits the capabilities of the algorithm.

35
Testing and Evaluation-Software

• I wrote the code in C, and then I went through
  the flowcharts and updated them.
• I made sure everything flowed logically in the
  code.
• I compiled the code, and finally had success
  after much troubleshooting. The code will
  definitely have errors, but without anything to
  test it on, I cannot find any more.
• There are some warnings about the pointers used
  in the transceiver code, but I tried fixing the
  syntax, and nothing helped.

36
Problems Encountered-Software

• I encountered many problems with the software,
  which have been mentioned previously.
• Needing integers for encryption and decryption to
  work
• MATLAB rounding errors
• Nothing to test code on
• Inadequate understanding of the algorithms
• Most of these have been fixed, but some are
  unresolved.
• My routines do not work well in MATLAB because of
  the rounding/cutoff of numbers.
• I still have nothing to test the C code on.

37
Problems Encountered-Hard/Software

• We came across an issue with the LCD in the
  breadboard.
• The LCD will not write characters.
• We thought the pins were mixed up, but switching
  pins did not help.
• The issue is still unresolved.

38
Problems Encountered-Hardware

• The values of the inductors and capacitors in the
  application circuit were very small.

39
Problems Encountered-Transceiver

• We had quite a few problems with the transceiver.
• Mentioned previously, we tried to build our own
  adaptor to put the chip on a breadboard, but that
  failed because of the small size.
• We didnt know how to write driver and
  initializer code.
• We finally ordered the application circuit, but
  we did that too late.

40
Lessons Learned-Transceiver

• We learned to ask around to see if there is a
  simpler transceiver that others know how to use.
• We learned to look for an application circuit
  early and use that rather than take the long way.
• The application circuit came with driver code,
  which saved a ton of time.

41
BUDGET
Item Per unit Cost Quantity Cost ()
PIC 18F4620 7.94 3 23.82
LCD 16X4 23.82 2 47.64
LM7805 0.6 3 1.2
Keypad 6.95 2 13.9
20 MHz crystal 1.7 2 2.14
RF Transceiver 1.99 2 3.98
Daughter Board For MRF49XA 39.99 2 79.98
Total 172.66

42
Software Future Work

• There is much work that could be done to improve
  the software algorithms for this project.
• Error checking code
• The transceiver code can be refined to work more
  efficiently.
• There may also be a need to use larger variable
  types or break the large numbers into smaller
  pieces to implement the larger encryption.

43
Software Future Work

• To be effective, the encryption needs to use
  larger numbers. The article that this idea came
  from stated that a 200-300 digit prime number was
  needed to make the algorithm secure.
• The rest of the requirements also need to be
  implemented.
• This includes digital signatures, which was one
  of our requirements as well
• Other requirements for the secure voting system
  are verifiability, robustness, and authorization.

44
Software Future Work

• There are many ways this code could be made
  better.
• One suggestion we received during our
  demonstration was to change our encryption
  numbers periodically and keep track of how many
  votes were recorded during certain time periods.
• This scheme could be implemented, and it would
  take a lot of work. It would be interesting.
• To take into consideration there would need to
  be a threshold number of votes before the numbers
  could change to ensure privacy.

45
Hardware Future Work

• Can redesign all the hardware
• Use a simpler transceiver such as the Xbee, which
  other groups have used successfully
• Include serial port interface on the PCB for
  downloading code directly to PIC without removing
  from PCB

46
Hardware Future Work

• Redesign PCB to be smaller
• Enclose in box
• Add batteries and switches to each module
• Many of these were supposed to be done this
  semester.

47
Summary

• We have software algorithms that work
• There is nothing to test the C code on
• Hardware does not work at all, though the circuit
  should be correct
• We did not implement digital signatures