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AnonymousVoting.sol
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AnonymousVoting.sol
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pragma solidity ^0.4.3;
/**
* @title ECCMath
*
* Functions for working with integers, curve-points, etc.
*
* @author Andreas Olofsson ([email protected])
*/
library ECCMath {
/// @dev Modular inverse of a (mod p) using euclid.
/// "a" and "p" must be co-prime.
/// @param a The number.
/// @param p The mmodulus.
/// @return x such that ax = 1 (mod p)
function invmod(uint a, uint p) internal constant returns (uint) {
if (a == 0 || a == p || p == 0)
throw;
if (a > p)
a = a % p;
int t1;
int t2 = 1;
uint r1 = p;
uint r2 = a;
uint q;
while (r2 != 0) {
q = r1 / r2;
(t1, t2, r1, r2) = (t2, t1 - int(q) * t2, r2, r1 - q * r2);
}
if (t1 < 0)
return (p - uint(-t1));
return uint(t1);
}
/// @dev Modular exponentiation, b^e % m
/// Basically the same as can be found here:
/// https:/ethereum/serpent/blob/develop/examples/ecc/modexp.se
/// @param b The base.
/// @param e The exponent.
/// @param m The modulus.
/// @return x such that x = b**e (mod m)
function expmod(uint b, uint e, uint m) internal constant returns (uint r) {
if (b == 0)
return 0;
if (e == 0)
return 1;
if (m == 0)
throw;
r = 1;
uint bit = 2 ** 255;
assembly {
loop:
jumpi(end, iszero(bit))
r := mulmod(mulmod(r, r, m), exp(b, iszero(iszero(and(e, bit)))), m)
r := mulmod(mulmod(r, r, m), exp(b, iszero(iszero(and(e, div(bit, 2))))), m)
r := mulmod(mulmod(r, r, m), exp(b, iszero(iszero(and(e, div(bit, 4))))), m)
r := mulmod(mulmod(r, r, m), exp(b, iszero(iszero(and(e, div(bit, 8))))), m)
bit := div(bit, 16)
jump(loop)
end:
}
}
/// @dev Converts a point (Px, Py, Pz) expressed in Jacobian coordinates to (Px", Py", 1).
/// Mutates P.
/// @param P The point.
/// @param zInv The modular inverse of "Pz".
/// @param z2Inv The square of zInv
/// @param prime The prime modulus.
/// @return (Px", Py", 1)
function toZ1(uint[3] memory P, uint zInv, uint z2Inv, uint prime) internal constant {
P[0] = mulmod(P[0], z2Inv, prime);
P[1] = mulmod(P[1], mulmod(zInv, z2Inv, prime), prime);
P[2] = 1;
}
/// @dev See _toZ1(uint[3], uint, uint).
/// Warning: Computes a modular inverse.
/// @param PJ The point.
/// @param prime The prime modulus.
/// @return (Px", Py", 1)
function toZ1(uint[3] PJ, uint prime) internal constant {
uint zInv = invmod(PJ[2], prime);
uint zInv2 = mulmod(zInv, zInv, prime);
PJ[0] = mulmod(PJ[0], zInv2, prime);
PJ[1] = mulmod(PJ[1], mulmod(zInv, zInv2, prime), prime);
PJ[2] = 1;
}
}
library Secp256k1 {
// TODO separate curve from crypto primitives?
// Field size
uint constant pp = 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFC2F;
// Base point (generator) G
uint constant Gx = 0x79BE667EF9DCBBAC55A06295CE870B07029BFCDB2DCE28D959F2815B16F81798;
uint constant Gy = 0x483ADA7726A3C4655DA4FBFC0E1108A8FD17B448A68554199C47D08FFB10D4B8;
// Order of G
uint constant nn = 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141;
// Cofactor
// uint constant hh = 1;
// Maximum value of s
uint constant lowSmax = 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0;
// For later
// uint constant lambda = "0x5363ad4cc05c30e0a5261c028812645a122e22ea20816678df02967c1b23bd72";
// uint constant beta = "0x7ae96a2b657c07106e64479eac3434e99cf0497512f58995c1396c28719501ee";
/// @dev See Curve.onCurve
function onCurve(uint[2] P) internal constant returns (bool) {
uint p = pp;
if (0 == P[0] || P[0] == p || 0 == P[1] || P[1] == p)
return false;
uint LHS = mulmod(P[1], P[1], p);
uint RHS = addmod(mulmod(mulmod(P[0], P[0], p), P[0], p), 7, p);
return LHS == RHS;
}
/// @dev See Curve.isPubKey
function isPubKey(uint[2] memory P) internal constant returns (bool isPK) {
isPK = onCurve(P);
}
/// @dev See Curve.isPubKey
// TODO: We assume we are given affine co-ordinates for now
function isPubKey(uint[3] memory P) internal constant returns (bool isPK) {
uint[2] memory a_P;
a_P[0] = P[0];
a_P[1] = P[1];
isPK = onCurve(a_P);
}
/// @dev See Curve.validateSignature
function validateSignature(bytes32 message, uint[2] rs, uint[2] Q) internal constant returns (bool) {
uint n = nn;
uint p = pp;
if(rs[0] == 0 || rs[0] >= n || rs[1] == 0 || rs[1] > lowSmax)
return false;
if (!isPubKey(Q))
return false;
uint sInv = ECCMath.invmod(rs[1], n);
uint[3] memory u1G = _mul(mulmod(uint(message), sInv, n), [Gx, Gy]);
uint[3] memory u2Q = _mul(mulmod(rs[0], sInv, n), Q);
uint[3] memory P = _add(u1G, u2Q);
if (P[2] == 0)
return false;
uint Px = ECCMath.invmod(P[2], p); // need Px/Pz^2
Px = mulmod(P[0], mulmod(Px, Px, p), p);
return Px % n == rs[0];
}
/// @dev See Curve.compress
function compress(uint[2] P) internal constant returns (uint8 yBit, uint x) {
x = P[0];
yBit = P[1] & 1 == 1 ? 1 : 0;
}
/// @dev See Curve.decompress
function decompress(uint8 yBit, uint x) internal constant returns (uint[2] P) {
uint p = pp;
var y2 = addmod(mulmod(x, mulmod(x, x, p), p), 7, p);
var y_ = ECCMath.expmod(y2, (p + 1) / 4, p);
uint cmp = yBit ^ y_ & 1;
P[0] = x;
P[1] = (cmp == 0) ? y_ : p - y_;
}
// Point addition, P + Q
// inData: Px, Py, Pz, Qx, Qy, Qz
// outData: Rx, Ry, Rz
function _add(uint[3] memory P, uint[3] memory Q) internal constant returns (uint[3] memory R) {
if(P[2] == 0)
return Q;
if(Q[2] == 0)
return P;
uint p = pp;
uint[4] memory zs; // Pz^2, Pz^3, Qz^2, Qz^3
zs[0] = mulmod(P[2], P[2], p);
zs[1] = mulmod(P[2], zs[0], p);
zs[2] = mulmod(Q[2], Q[2], p);
zs[3] = mulmod(Q[2], zs[2], p);
uint[4] memory us = [
mulmod(P[0], zs[2], p),
mulmod(P[1], zs[3], p),
mulmod(Q[0], zs[0], p),
mulmod(Q[1], zs[1], p)
]; // Pu, Ps, Qu, Qs
if (us[0] == us[2]) {
if (us[1] != us[3])
return;
else {
return _double(P);
}
}
uint h = addmod(us[2], p - us[0], p);
uint r = addmod(us[3], p - us[1], p);
uint h2 = mulmod(h, h, p);
uint h3 = mulmod(h2, h, p);
uint Rx = addmod(mulmod(r, r, p), p - h3, p);
Rx = addmod(Rx, p - mulmod(2, mulmod(us[0], h2, p), p), p);
R[0] = Rx;
R[1] = mulmod(r, addmod(mulmod(us[0], h2, p), p - Rx, p), p);
R[1] = addmod(R[1], p - mulmod(us[1], h3, p), p);
R[2] = mulmod(h, mulmod(P[2], Q[2], p), p);
}
// Point addition, P + Q. P Jacobian, Q affine.
// inData: Px, Py, Pz, Qx, Qy
// outData: Rx, Ry, Rz
function _addMixed(uint[3] memory P, uint[2] memory Q) internal constant returns (uint[3] memory R) {
if(P[2] == 0)
return [Q[0], Q[1], 1];
if(Q[1] == 0)
return P;
uint p = pp;
uint[2] memory zs; // Pz^2, Pz^3, Qz^2, Qz^3
zs[0] = mulmod(P[2], P[2], p);
zs[1] = mulmod(P[2], zs[0], p);
uint[4] memory us = [
P[0],
P[1],
mulmod(Q[0], zs[0], p),
mulmod(Q[1], zs[1], p)
]; // Pu, Ps, Qu, Qs
if (us[0] == us[2]) {
if (us[1] != us[3]) {
P[0] = 0;
P[1] = 0;
P[2] = 0;
return;
}
else {
_double(P);
return;
}
}
uint h = addmod(us[2], p - us[0], p);
uint r = addmod(us[3], p - us[1], p);
uint h2 = mulmod(h, h, p);
uint h3 = mulmod(h2, h, p);
uint Rx = addmod(mulmod(r, r, p), p - h3, p);
Rx = addmod(Rx, p - mulmod(2, mulmod(us[0], h2, p), p), p);
R[0] = Rx;
R[1] = mulmod(r, addmod(mulmod(us[0], h2, p), p - Rx, p), p);
R[1] = addmod(R[1], p - mulmod(us[1], h3, p), p);
R[2] = mulmod(h, P[2], p);
}
// Same as addMixed but params are different and mutates P.
function _addMixedM(uint[3] memory P, uint[2] memory Q) internal constant {
if(P[1] == 0) {
P[0] = Q[0];
P[1] = Q[1];
P[2] = 1;
return;
}
if(Q[1] == 0)
return;
uint p = pp;
uint[2] memory zs; // Pz^2, Pz^3, Qz^2, Qz^3
zs[0] = mulmod(P[2], P[2], p);
zs[1] = mulmod(P[2], zs[0], p);
uint[4] memory us = [
P[0],
P[1],
mulmod(Q[0], zs[0], p),
mulmod(Q[1], zs[1], p)
]; // Pu, Ps, Qu, Qs
if (us[0] == us[2]) {
if (us[1] != us[3]) {
P[0] = 0;
P[1] = 0;
P[2] = 0;
return;
}
else {
_doubleM(P);
return;
}
}
uint h = addmod(us[2], p - us[0], p);
uint r = addmod(us[3], p - us[1], p);
uint h2 = mulmod(h, h, p);
uint h3 = mulmod(h2, h, p);
uint Rx = addmod(mulmod(r, r, p), p - h3, p);
Rx = addmod(Rx, p - mulmod(2, mulmod(us[0], h2, p), p), p);
P[0] = Rx;
P[1] = mulmod(r, addmod(mulmod(us[0], h2, p), p - Rx, p), p);
P[1] = addmod(P[1], p - mulmod(us[1], h3, p), p);
P[2] = mulmod(h, P[2], p);
}
// Point doubling, 2*P
// Params: Px, Py, Pz
// Not concerned about the 1 extra mulmod.
function _double(uint[3] memory P) internal constant returns (uint[3] memory Q) {
uint p = pp;
if (P[2] == 0)
return;
uint Px = P[0];
uint Py = P[1];
uint Py2 = mulmod(Py, Py, p);
uint s = mulmod(4, mulmod(Px, Py2, p), p);
uint m = mulmod(3, mulmod(Px, Px, p), p);
var Qx = addmod(mulmod(m, m, p), p - addmod(s, s, p), p);
Q[0] = Qx;
Q[1] = addmod(mulmod(m, addmod(s, p - Qx, p), p), p - mulmod(8, mulmod(Py2, Py2, p), p), p);
Q[2] = mulmod(2, mulmod(Py, P[2], p), p);
}
// Same as double but mutates P and is internal only.
function _doubleM(uint[3] memory P) internal constant {
uint p = pp;
if (P[2] == 0)
return;
uint Px = P[0];
uint Py = P[1];
uint Py2 = mulmod(Py, Py, p);
uint s = mulmod(4, mulmod(Px, Py2, p), p);
uint m = mulmod(3, mulmod(Px, Px, p), p);
var PxTemp = addmod(mulmod(m, m, p), p - addmod(s, s, p), p);
P[0] = PxTemp;
P[1] = addmod(mulmod(m, addmod(s, p - PxTemp, p), p), p - mulmod(8, mulmod(Py2, Py2, p), p), p);
P[2] = mulmod(2, mulmod(Py, P[2], p), p);
}
// Multiplication dP. P affine, wNAF: w=5
// Params: d, Px, Py
// Output: Jacobian Q
function _mul(uint d, uint[2] memory P) internal constant returns (uint[3] memory Q) {
uint p = pp;
if (d == 0) // TODO
return;
uint dwPtr; // points to array of NAF coefficients.
uint i;
// wNAF
assembly
{
let dm := 0
dwPtr := mload(0x40)
mstore(0x40, add(dwPtr, 512)) // Should lower this.
loop:
jumpi(loop_end, iszero(d))
jumpi(even, iszero(and(d, 1)))
dm := mod(d, 32)
mstore8(add(dwPtr, i), dm) // Don"t store as signed - convert when reading.
d := add(sub(d, dm), mul(gt(dm, 16), 32))
even:
d := div(d, 2)
i := add(i, 1)
jump(loop)
loop_end:
}
// Pre calculation
uint[3][8] memory PREC; // P, 3P, 5P, 7P, 9P, 11P, 13P, 15P
PREC[0] = [P[0], P[1], 1];
var X = _double(PREC[0]);
PREC[1] = _addMixed(X, P);
PREC[2] = _add(X, PREC[1]);
PREC[3] = _add(X, PREC[2]);
PREC[4] = _add(X, PREC[3]);
PREC[5] = _add(X, PREC[4]);
PREC[6] = _add(X, PREC[5]);
PREC[7] = _add(X, PREC[6]);
uint[16] memory INV;
INV[0] = PREC[1][2]; // a1
INV[1] = mulmod(PREC[2][2], INV[0], p); // a2
INV[2] = mulmod(PREC[3][2], INV[1], p); // a3
INV[3] = mulmod(PREC[4][2], INV[2], p); // a4
INV[4] = mulmod(PREC[5][2], INV[3], p); // a5
INV[5] = mulmod(PREC[6][2], INV[4], p); // a6
INV[6] = mulmod(PREC[7][2], INV[5], p); // a7
INV[7] = ECCMath.invmod(INV[6], p); // a7inv
INV[8] = INV[7]; // aNinv (a7inv)
INV[15] = mulmod(INV[5], INV[8], p); // z7inv
for(uint k = 6; k >= 2; k--) { // z6inv to z2inv
INV[8] = mulmod(PREC[k + 1][2], INV[8], p);
INV[8 + k] = mulmod(INV[k - 2], INV[8], p);
}
INV[9] = mulmod(PREC[2][2], INV[8], p); // z1Inv
for(k = 0; k < 7; k++) {
ECCMath.toZ1(PREC[k + 1], INV[k + 9], mulmod(INV[k + 9], INV[k + 9], p), p);
}
// Mult loop
while(i > 0) {
uint dj;
uint pIdx;
i--;
assembly {
dj := byte(0, mload(add(dwPtr, i)))
}
_doubleM(Q);
if (dj > 16) {
pIdx = (31 - dj) / 2; // These are the "negative ones", so invert y.
_addMixedM(Q, [PREC[pIdx][0], p - PREC[pIdx][1]]);
}
else if (dj > 0) {
pIdx = (dj - 1) / 2;
_addMixedM(Q, [PREC[pIdx][0], PREC[pIdx][1]]);
}
}
}
}
contract owned {
address public owner;
/* Initialise contract creator as owner */
function owned() {
owner = msg.sender;
}
/* Function to dictate that only the designated owner can call a function */
modifier onlyOwner {
if(owner != msg.sender) throw;
_;
}
/* Transfer ownership of this contract to someone else */
function transferOwnership(address newOwner) onlyOwner() {
owner = newOwner;
}
}
/*
* @title AnonymousVoting
* Open Vote Network
* A self-talling protocol that supports voter privacy.
*
* Author: Patrick McCorry
*/
contract AnonymousVoting is owned {
// Modulus for public keys
uint constant pp = 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFC2F;
// Base point (generator) G
uint constant Gx = 0x79BE667EF9DCBBAC55A06295CE870B07029BFCDB2DCE28D959F2815B16F81798;
uint constant Gy = 0x483ADA7726A3C4655DA4FBFC0E1108A8FD17B448A68554199C47D08FFB10D4B8;
// Modulus for private keys (sub-group)
uint constant nn = 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141;
uint[2] G;
//Every address has an index
//This makes looping in the program easier.
address[] public addresses;
mapping (address => uint) public addressid; // Address to Counter
mapping (uint => Voter) public voters;
mapping (address => bool) public eligible; // White list of addresses allowed to vote
mapping (address => bool) public registered; // Address registered?
mapping (address => bool) public votecast; // Address voted?
mapping (address => bool) public commitment; // Have we received their commitment?
mapping (address => uint) public refunds; // Have we received their commitment?
struct Voter {
address addr;
uint[2] registeredkey;
uint[2] reconstructedkey;
bytes32 commitment;
uint[2] vote;
}
// Work around function to fetch details about a voter
function getVoter() returns (uint[2] _registeredkey, uint[2] _reconstructedkey, bytes32 _commitment){
uint index = addressid[msg.sender];
_registeredkey = voters[index].registeredkey;
_reconstructedkey = voters[index].reconstructedkey;
_commitment = voters[index].commitment;
}
// List of timers that each phase MUST end by an explicit time in UNIX timestamp.
// Ethereum works in SECONDS. Not milliseconds.
uint public finishSignupPhase; // Election Authority to transition to next phase.
uint public endSignupPhase; // Election Authority does not transition to next phase by this time.
uint public endCommitmentPhase; // Voters have not sent their commitments in by this time.
uint public endVotingPhase; // Voters have not submitted their vote by this stage.
uint public endRefundPhase; // Voters must claim their refund by this stage.
uint public totalregistered; //Total number of participants that have submited a voting key
uint public totaleligible;
uint public totalcommitted;
uint public totalvoted;
uint public totalrefunded;
uint public totaltorefund;
string public question;
uint[2] public finaltally; // Final tally
bool public commitmentphase; // OPTIONAL phase.
uint public depositrequired;
uint public gap; // Minimum amount of time between time stamps.
address public charity;
// TODO: Why cant election authority receive the spoils?
uint public lostdeposit; // This money is collected from non active voters...
enum State { SETUP, SIGNUP, COMMITMENT, VOTE, FINISHED }
State public state;
modifier inState(State s) {
if(state != s) {
throw;
}
_;
}
// 2 round anonymous voting protocol
// TODO: Right now due to gas limits there is an upper limit
// on the number of participants that we can have voting...
// I need to split the functions up... so if they cannot
// finish their entire workload in 1 transaction, then
// it does the maximum. This way we can chain transactions
// to complete the job...
function AnonymousVoting(uint _gap, address _charity) {
G[0] = Gx;
G[1] = Gy;
state = State.SETUP;
question = "No question set";
gap = _gap; // Minimum gap period between stages
charity = _charity;
}
// Owner of contract sets a whitelist of addresses that are eligible to vote.
function setEligible(address[] addr) onlyOwner {
// We can only handle up 50 people at the moment.
if(totaleligible > 50) {
throw;
}
// Sign up the addresses
for(uint i=0; i<addr.length; i++) {
if(!eligible[addr[i]]) {
eligible[addr[i]] = true;
addresses.push(addr[i]);
totaleligible += 1;
}
}
}
// Owner of contract declares that eligible addresses begin round 1 of the protocol
// Time is the number of 'blocks' we must wait until we can move onto round 2.
function beginSignUp(string _question, bool enableCommitmentPhase, uint _finishSignupPhase, uint _endSignupPhase, uint _endCommitmentPhase, uint _endVotingPhase, uint _endRefundPhase, uint _depositrequired) inState(State.SETUP) onlyOwner payable returns (bool){
// We have lots of timers. let's explain each one
// _finishSignUpPhase - Voters should be signed up before this timer
// Voter is refunded if any of the timers expire:
// _endSignUpPhase - Election Authority never finished sign up phase
// _endCommitmentPhase - One or more voters did not send their commitments in time
// _endVotingPhase - One or more voters did not send their votes in time
// _endRefundPhase - Provide time for voters to get their money back.
// Why is there no endTally? Because anyone can call it!
// Represented in UNIX time...
// TODO: Set to block timestamp...
// TODO: Enforce gap to be at least 1 hour.. may break unit testing
// Make sure 3 people are at least eligible to vote..
// Deposit can be zero or more WEI
if(_finishSignupPhase > 0 + gap && addresses.length >= 3 && _depositrequired >= 0) {
// Ensure each time phase finishes in the future...
// Ensure there is a gap of 'x time' between each phase.
if(_endSignupPhase-gap < _finishSignupPhase) {
return false;
}
// We need to check Commitment timestamps if phase is enabled.
if(enableCommitmentPhase) {
// Make sure there is a gap between 'end of registration' and 'end of commitment' phases.
if(_endCommitmentPhase-gap < _endSignupPhase) {
return false;
}
// Make sure there is a gap between 'end of commitment' and 'end of vote' phases.
if(_endVotingPhase-gap < _endCommitmentPhase) {
return false;
}
} else {
// We have no commitment phase.
// Make sure there is a gap between 'end of registration' and 'end of vote' phases.
if(_endVotingPhase-gap < _endSignupPhase) {
return false;
}
}
// Provide time for people to get a refund once the voting phase has ended.
if(_endRefundPhase-gap < _endVotingPhase) {
return false;
}
// Require Election Authority to deposit ether.
if(msg.value != _depositrequired) {
return false;
}
// Store the election authority's deposit
// Note: This deposit is only lost if the
// election authority does not begin the election
// or call the tally function before the timers expire.
refunds[msg.sender] = msg.value;
// All time stamps are reasonable.
// We can now begin the signup phase.
state = State.SIGNUP;
// All timestamps should be in UNIX..
finishSignupPhase = _finishSignupPhase;
endSignupPhase = _endSignupPhase;
endCommitmentPhase = _endCommitmentPhase;
endVotingPhase = _endVotingPhase;
endRefundPhase = _endRefundPhase;
question = _question;
commitmentphase = enableCommitmentPhase;
depositrequired = _depositrequired; // Deposit required from all voters
return true;
}
return false;
}
// This function determines if one of the deadlines have been missed
// If a deadline has been missed - then we finish the election,
// and allocate refunds to the correct people depending on the situation.
function deadlinePassed() returns (bool){
uint refund = 0;
// Has the Election Authority missed the signup deadline?
// Election Authority will forfeit his deposit.
if(state == State.SIGNUP && block.timestamp > endSignupPhase) {
// Nothing to do. All voters are refunded.
state = State.FINISHED;
totaltorefund = totalregistered;
// Election Authority forfeits his deposit...
// If 3 or more voters had signed up...
if(addresses.length >= 3) {
// Election Authority forfeits deposit
refund = refunds[owner];
refunds[owner] = 0;
lostdeposit = lostdeposit + refund;
}
return true;
}
// Has a voter failed to send their commitment?
// Election Authority DOES NOT forgeit his deposit.
if(state == State.COMMITMENT && block.timestamp > endCommitmentPhase) {
// Check which voters have not sent their commitment
for(uint i=0; i<totalregistered; i++) {
// Voters forfeit their deposit if failed to send a commitment
if(!commitment[voters[i].addr]) {
refund = refunds[voters[i].addr];
refunds[voters[i].addr] = 0;
lostdeposit = lostdeposit + refund;
} else {
// We will need to refund this person.
totaltorefund = totaltorefund + 1;
}
}
state = State.FINISHED;
return true;
}
// Has a voter failed to send in their vote?
// Eletion Authority does NOT forfeit his deposit.
if(state == State.VOTE && block.timestamp > endVotingPhase) {
// Check which voters have not cast their vote
for(i=0; i<totalregistered; i++) {
// Voter forfeits deposit if they have not voted.
if(!votecast[voters[i].addr]) {
refund = refunds[voters[i].addr];
refunds[voters[i].addr] = 0;
lostdeposit = lostdeposit + refund;
} else {
// Lets make sure refund has not already been issued...
if(refunds[voters[i].addr] > 0) {
// We will need to refund this person.
totaltorefund = totaltorefund + 1;
}
}
}
state = State.FINISHED;
return true;
}
// Has the deadline passed for voters to claim their refund?
// Only owner can call. Owner must be refunded (or forfeited).
// Refund period is over or everyone has already been refunded.
if(state == State.FINISHED && msg.sender == owner && refunds[owner] == 0 && (block.timestamp > endRefundPhase || totaltorefund == totalrefunded)) {
// Collect all unclaimed refunds. We will send it to charity.
for(i=0; i<totalregistered; i++) {
refund = refunds[voters[i].addr];
refunds[voters[i].addr] = 0;
lostdeposit = lostdeposit + refund;
}
uint[2] memory empty;
for(i=0; i<addresses.length; i++) {
address addr = addresses[i];
eligible[addr] = false; // No longer eligible
registered[addr] = false; // Remove voting registration
voters[i] = Voter({addr: 0, registeredkey: empty, reconstructedkey: empty, vote: empty, commitment: 0});
addressid[addr] = 0; // Remove index
votecast[addr] = false; // Remove that vote was cast
commitment[addr] = false;
}
// Reset timers.
finishSignupPhase = 0;
endSignupPhase = 0;
endCommitmentPhase = 0;
endVotingPhase = 0;
endRefundPhase = 0;
delete addresses;
// Keep track of voter activity
totalregistered = 0;
totaleligible = 0;
totalcommitted = 0;
totalvoted = 0;
// General values that need reset
question = "No question set";
finaltally[0] = 0;
finaltally[1] = 0;
commitmentphase = false;
depositrequired = 0;
totalrefunded = 0;
totaltorefund = 0;
state = State.SETUP;
return true;
}
// No deadlines have passed...
return false;
}
// Called by participants to register their voting public key
// Participant mut be eligible, and can only register the first key sent key.
function register(uint[2] xG, uint[3] vG, uint r) inState(State.SIGNUP) payable returns (bool) {
// HARD DEADLINE
if(block.timestamp > finishSignupPhase) {
throw; // throw returns the voter's ether, but exhausts their gas.
}
// Make sure the ether being deposited matches what we expect.
if(msg.value != depositrequired) {
return false;
}
// Only white-listed addresses can vote
if(eligible[msg.sender]) {
if(verifyZKP(xG,r,vG) && !registered[msg.sender]) {
// Store deposit
refunds[msg.sender] = msg.value;
// Update voter's registration
uint[2] memory empty;
addressid[msg.sender] = totalregistered;
voters[totalregistered] = Voter({addr: msg.sender, registeredkey: xG, reconstructedkey: empty, vote: empty, commitment: 0});
registered[msg.sender] = true;
totalregistered += 1;
return true;
}
}
return false;
}
// Timer has expired - we want to start computing the reconstructed keys
function finishRegistrationPhase() inState(State.SIGNUP) onlyOwner returns(bool) {
// Make sure at least 3 people have signed up...
if(totalregistered < 3) {
return;
}
// We can only compute the public keys once participants
// have been given an opportunity to register their
// voting public key.
if(block.timestamp < finishSignupPhase) {
return;
}
// Election Authority has a deadline to begin election
if(block.timestamp > endSignupPhase) {
return;
}
uint[2] memory temp;
uint[3] memory yG;
uint[3] memory beforei;
uint[3] memory afteri;
// Step 1 is to compute the index 1 reconstructed key
afteri[0] = voters[1].registeredkey[0];
afteri[1] = voters[1].registeredkey[1];
afteri[2] = 1;
for(uint i=2; i<totalregistered; i++) {
Secp256k1._addMixedM(afteri, voters[i].registeredkey);
}
ECCMath.toZ1(afteri,pp);
voters[0].reconstructedkey[0] = afteri[0];
voters[0].reconstructedkey[1] = pp - afteri[1];
// Step 2 is to add to beforei, and subtract from afteri.
for(i=1; i<totalregistered; i++) {
if(i==1) {
beforei[0] = voters[0].registeredkey[0];
beforei[1] = voters[0].registeredkey[1];
beforei[2] = 1;
} else {
Secp256k1._addMixedM(beforei, voters[i-1].registeredkey);
}
// If we have reached the end... just store beforei
// Otherwise, we need to compute a key.
// Counting from 0 to n-1...
if(i==(totalregistered-1)) {
ECCMath.toZ1(beforei,pp);
voters[i].reconstructedkey[0] = beforei[0];
voters[i].reconstructedkey[1] = beforei[1];
} else {
// Subtract 'i' from afteri
temp[0] = voters[i].registeredkey[0];
temp[1] = pp - voters[i].registeredkey[1];
// Grab negation of afteri (did not seem to work with Jacob co-ordinates)
Secp256k1._addMixedM(afteri,temp);
ECCMath.toZ1(afteri,pp);
temp[0] = afteri[0];
temp[1] = pp - afteri[1];
// Now we do beforei - afteri...
yG = Secp256k1._addMixed(beforei, temp);
ECCMath.toZ1(yG,pp);
voters[i].reconstructedkey[0] = yG[0];
voters[i].reconstructedkey[1] = yG[1];
}
}
// We have computed each voter's special voting key.
// Now we either enter the commitment phase (option) or voting phase.
if(commitmentphase) {
state = State.COMMITMENT;
} else {
state = State.VOTE;
}
}
/*
* OPTIONAL STAGE: All voters submit the hash of their vote.
* Why? The final voter that submits their vote gets to see the tally result
* before anyone else. This provides the voter with an additional advantage
* compared to all other voters. To get around this issue; we can force all
* voters to commit to their vote in advance.... and votes are only revealed
* once all voters have committed. This way the final voter has no additional
* advantage as they cannot change their vote depending on the tally.
* However... we cannot enforce the pre-image to be a hash, and someone could
* a commitment that is not a vote. This will break the election, but you
* will be able to determine who did it (and possibly punish them!).
*/
function submitCommitment(bytes32 h) inState(State.COMMITMENT) {
//All voters have a deadline to send their commitment
if(block.timestamp > endCommitmentPhase) {
return;
}
if(!commitment[msg.sender]) {
commitment[msg.sender] = true;
uint index = addressid[msg.sender];
voters[index].commitment = h;
totalcommitted = totalcommitted + 1;
// Once we have recorded all commitments... let voters vote!
if(totalcommitted == totalregistered) {
state = State.VOTE;
}
}
}
// Given the 1 out of 2 ZKP - record the users vote!
function submitVote(uint[4] params, uint[2] y, uint[2] a1, uint[2] b1, uint[2] a2, uint[2] b2) inState(State.VOTE) returns (bool) {
// HARD DEADLINE
if(block.timestamp > endVotingPhase) {
return;
}
uint c = addressid[msg.sender];
// Make sure the sender can vote, and hasn't already voted.
if(registered[msg.sender] && !votecast[msg.sender]) {
// OPTIONAL Phase: Voters need to commit to their vote in advance.
// Time to verify if this vote matches the voter's previous commitment.
if(commitmentphase) {
// Voter has previously committed to the entire zero knowledge proof...
bytes32 h = sha3(msg.sender, params, voters[c].registeredkey, voters[c].reconstructedkey, y, a1, b1, a2, b2);
// No point verifying the ZKP if it doesn't match the voter's commitment.
if(voters[c].commitment != h) {
return false;
}
}
// Verify the ZKP for the vote being cast
if(verify1outof2ZKP(params, y, a1, b1, a2, b2)) {
voters[c].vote[0] = y[0];
voters[c].vote[1] = y[1];
votecast[msg.sender] = true;
totalvoted += 1;
// Refund the sender their ether..
// Voter has finished their part of the protocol...
uint refund = refunds[msg.sender];
refunds[msg.sender] = 0;
// We can still fail... Safety first.
// If failed... voter can call withdrawRefund()
// to collect their money once the election has finished.
if (!msg.sender.send(refund)) {
refunds[msg.sender] = refund;
}
return true;
}
}
// Either vote has already been cast, or ZKP verification failed.
return false;
}
// Assuming all votes have been submitted. We can leak the tally.
// We assume Election Authority performs this function. It could be anyone.
// Election Authority gets deposit upon tallying.
// TODO: Anyone can do this function. Perhaps remove refund code - and force Election Authority
// to explicit withdraw it? Election cannot reset until he is refunded - so that should be OK
function computeTally() inState(State.VOTE) onlyOwner {
uint[3] memory temp;
uint[2] memory vote;