public static PVSSEngine getInstance(int n, int t, int numBits) throws InvalidVSSScheme {
if (t > n) {
throw new InvalidVSSScheme("(t,n)=(" + t + "," + n + ")");
}
/** Fill in public information */
BigInteger groupPrimeOrder = new BigInteger("2373168401");
BigInteger generatorg = new BigInteger("1964832733");
BigInteger generatorG = new BigInteger("1476385517");
// System.out.println("groupPrimeOrder : " + groupPrimeOrder);
// System.out.println("generatorg : " + generatorg);
// System.out.println("generatorG : " + generatorG);
/*
* Initialize public information structure
*/
PublicInfo publicInfo = new PublicInfo(n, t, groupPrimeOrder, generatorg, generatorG);
/*
* Generate interpolation points
*/
publicInfo.setInterpolationPoints();
return new PVSSEngine(publicInfo);
}
public static BigInteger hash(PublicInfo info, byte[] data) throws InvalidVSSScheme {
try {
if (md == null) {
md = MessageDigest.getInstance(info.getHashAlgorithm());
} else {
md.reset();
}
return new BigInteger(md.digest(data));
} catch (NoSuchAlgorithmException e) {
throw new InvalidVSSScheme("Invalid hash algorithm " + info.getHashAlgorithm());
}
}
public static boolean addMujiInfo(String accountNum, String password) {
String sql = "insert into " + CreateWord.MUJITable + "(accountNum,password) values(?,?)";
try {
Class.forName(driver);
conn = PublicInfo.getConnection();
ps = conn.prepareStatement(sql);
ps.setString(1, accountNum);
ps.setString(2, password);
ps.executeUpdate();
return true;
} catch (ClassNotFoundException | SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return false;
}
public static PVSSEngine getInstance(PublicInfo publicInfo) throws InvalidVSSScheme {
publicInfo.setInterpolationPoints();
return new PVSSEngine(publicInfo);
}
public BigInteger combineShares(int x[], Share[] shares) throws Exception {
int t = publicInfo.getT();
int n = publicInfo.getN();
BigInteger[] z = this.publicInfo.getInterpolationPoints();
if (x.length != t) {
throw new RuntimeException("There must be " + t + " diferent and valid shares");
}
for (int i : x) {
if (shares[i] == null) {
throw new RuntimeException("There must be " + t + " diferent and valid shares");
}
}
BigInteger q = publicInfo.getGroupPrimeOrder();
BigInteger qm1 = q.subtract(BigInteger.ONE);
BigInteger secret = BigInteger.ONE;
// System.out.print("PVSSEngine.combineShares: Using shares");
for (int i = 0; i < t; i++) { // iterates over x[i]
// System.out.print(" "+x[i]);
/*
* float lambda = 1; for(int j=0; j<t; j++) { //iterates over x[j]
* if(j != i){ lambda = lambda*((float)(x[j]+1)/(float)(x[j]-x[i]));
* } }
*
* secret = secret.multiply(shares[x[i]].getShare()
.modPow(BigInteger.valueOf((long)lambda),q)).mod(q);
*/
BigInteger lambda = BigInteger.ONE;
BigInteger lambdadenom = BigInteger.ONE;
BigInteger lambdanumer = BigInteger.ONE;
BigInteger gcd = BigInteger.ONE;
for (int j = 0; j < t; j++) { // iterates over x[j]
if (j != i) {
// It,s essential that mod is not done here, because of gcd
lambdanumer = lambdanumer.multiply(z[x[j]]);
lambdadenom = lambdadenom.multiply(z[x[j]].subtract(z[x[i]]));
}
}
// System.out.println("lambdanumer " + lambdanumer + ", lambdadenom " + lambdadenom);
gcd = lambdadenom.gcd(lambdanumer);
lambdadenom = lambdadenom.divide(gcd);
lambdanumer = lambdanumer.divide(gcd);
/** Sanity check * */
gcd = lambdadenom.gcd(qm1);
// System.out.println("GCD :" + gcd.intValue());
if (gcd.intValue() != 1) {
// System.out.println("i :" + i);
// System.out.println("lambdanumer " + lambdanumer);
// System.out.println("lambdadenom " + lambdadenom);
// System.out.println("z array :" + Arrays.toString(z));
// System.out.println("x array :" + Arrays.toString(x));
throw invalidLagrangeCoeff();
}
BigInteger invdenom = lambdadenom.modInverse(qm1);
lambda = lambdanumer.multiply(invdenom).mod(qm1);
// System.out.println("i = " + i + ", lambda = " + lambda + ", lambdanumer "
// + lambdanumer + ", lambdadenom " + lambdadenom);
secret = secret.multiply(shares[x[i]].getShare().modPow(lambda, q)).mod(q);
}
/*
* BigInteger secret = BigInteger.ONE;
*
* //System.out.print("PVSSEngine.combineShares: Using shares"); for(int
* i=0; i<t; i++){ //iterates over x[i] //System.out.print(" "+x[i]);
*
* BigInteger lambda2 = BigInteger.valueOf(1); for(int j=0; j<t; j++) {
* //iterates over x[j] if(j != i){
*
* BigInteger denominator = BigInteger.valueOf(x[j]-x[i]); lambda2 =
* lambda2.multiply( BigInteger.valueOf((x[j]+1)).multiply(
* denominator.modInverse(q)) ).mod(qm1); } }
*
* System.out.println("shares[x[i]].getShare()
* ="+shares[x[i]].getShare()); System.out.println("Our lambda2 :
* "+lambda2); System.out.println("q : "+q);
*
* BigInteger temp2 = (shares[x[i]].getShare()).modPow(lambda2,q);
* System.out.println("temp2 ="+temp2); *
* float lambda = 1; for(int j=0; j<t; j++) { //iterates over x[j] if(j
* != i){ lambda = lambda*((float)(x[j]+1)/(float)(x[j]-x[i])); } }
*
* BigInteger temp1 =
* shares[x[i]].getShare().modPow(BigInteger.valueOf((long)lambda),q);
* System.out.println("lambda : "+lambda); System.out.println("temp1
* ="+temp1);
*
* System.out.println("q : "+q);
*
* secret =
* secret.multiply(shares[x[i]].getShare().modPow(BigInteger.valueOf((long)lambda),q)).mod(q);
}
*/
// System.out.println("Secret returning from combine share :" + secret);
return secret;
}
