Cryptographic Applications - Introduction to Cryptography with Java Applets - page 347

System.out.println
(“Enter the number of challenges to issue per respondent:”);
trials=Integer.parseInt(k.readLine());
r=new SecureRandom();
//Bind the challenger to port 12345
ServerSocket ss=new ServerSocket(12345);
//Loop forever
while (true) {
//Create a new thread for every incoming connection
//this allows challenger to handle multiple respondents
Challenger c=new Challenger(ss.accept());
c.start();
}
}
public void run() {
try {
System.out.println(“Request received from “
+socket.getInetAddress().toString());
//Create the IO streams
PrintStream out=new PrintStream(socket.getOutputStream());
BufferedReader in=new BufferedReader
(new InputStreamReader(socket.getInputStream()));
//Read in modulus and s key values
//These should be checked against a database with a TTP
BigInteger modulus=new BigInteger(in.readLine());
BigInteger s=new BigInteger(in.readLine());
BigInteger[] z=new BigInteger[2];
//Begin challenging the respondent
for (int i=0;i<trials;i++) {
//Read in z1 and z2; here labeled z0 and z1 for convenience
z[0]=new BigInteger(in.readLine());
z[1]=new BigInteger(in.readLine());
//Check that their product = s
if (!z[0].multiply(z[1]).mod(modulus).equals(s)) {
System.out.println(“Product not congruent to s-closing connection”);
break;
}
//Issue the challenge-a random 0 or 1
int challenge=Math.abs(r.nextInt())%2;
out.println(challenge);
//Get the response
BigInteger response=new BigInteger(in.readLine());