WVjBMyk4

1import java.math.BigInteger;
2import java.security.SecureRandom;
3import java.util.Random;
4
5public class ElgamalBatchVerification {
6    public static void main(String[] args) {
7//Key Generation 
8        Random random = new SecureRandom();
9        BigInteger secretKey = new BigInteger("123456789987654321");
10        BigInteger p = BigInteger.probablePrime(64, random);
11        BigInteger g = new BigInteger("3");
12        BigInteger y = g.modPow(secretKey, p);
13        
14//public key (q,g,y)
15//Sign
16        String[] messages = {"4564468461684516161651686", "987979851684656846518651826","654654845684865181548351685", "789746543548646813521831535","32546461168531211316513168", "8789486434846515486165184615","321321584345684484548354355", "3211231218486854546358", "323131335485684358355","456456456464684646516845465","65646465461684516161651686", "789464351684656846518651826","351646845684865181548351685", "13165463548646813521831535", "1168531211316513168","536465464115486165184615", "345534564654156548354355", "4561324546358","354878451558355", "46468464456845465"};
17
18        BigInteger[] r = new BigInteger[messages.length];
19        BigInteger[] s = new BigInteger[messages.length];
20        BigInteger m, k;
21        
22        for (int i = 0; i < messages.length; i++) {
23            m = new BigInteger(messages[i]);
24            k = BigInteger.probablePrime(64, random);
25            r[i] = g.modPow(k, p);
26            s[i] = ((new BigInteger(m.hashCode() +"")).subtract(secretKey.multiply(r[i]))).multiply(k.modInverse(p.subtract(new BigInteger("1"))));
27        }
28
29//Normal Verification
30        BigInteger normal_rhs, normal_lhs;
31        long normal_start = System.nanoTime();
32        for (int i = 0; i < messages.length; i++) {
33            normal_rhs = g.modPow(new BigInteger((new BigInteger(messages[i])).hashCode() + ""), p);
34            normal_lhs = y.modPow(r[i], p).multiply(r[i].modPow(s[i], p)).mod(p);
35            if (normal_rhs.equals(normal_lhs)) {
36                System.out.println("Sign " + i + " : true");
37            } else {
38                System.out.println("Sign " + i + " : false");
39            }
40        }
41
42        long normal_end = System.nanoTime();
43        System.out.println("normal verification time"+(normal_end - normal_start));
44        BigInteger yr_multiplication = new BigInteger("1");
45        BigInteger sumhm = new BigInteger("0");
46
47        long batch_start = System.nanoTime();
48        for (int i = 0; i < messages.length; i++) {
49            sumhm = sumhm.add(new BigInteger((new BigInteger(messages[i])).hashCode() + ""));
50            yr_multiplication = yr_multiplication.multiply(y.modPow(r[i], p).multiply(r[i].modPow(s[i],p)).mod(p));
51        }
52
53        BigInteger batch_rhs = g.modPow(sumhm, p);
54        BigInteger batch_lhs = yr_multiplication.mod(p);
55
56        if (batch_rhs.equals(batch_lhs)) {
57            System.out.println("batch signatures verified");
58        } else {
59            System.out.println("exists forged sigantures");
60        }
61
62        long batch_end = System.nanoTime();
63        System.out.println("batch verification time "+(batch_end - batch_start));
64    }
65}