Generating and Verifying Signatures

Prepare Initial Program Structure

Here's the basic structure of the GenSig program created by this lesson. Place it in a file called GenSig.java:

import java.io.*;
import java.security.*;

class GenSig {

    public static void main(String[] args) {

        /* Generate a DSA signature */

        if (args.length != 1) {
            System.out.println("Usage: GenSig nameOfFileToSign");
            }
        else try {

        // the rest of the code goes here

        } catch (Exception e) {
            System.err.println("Caught exception " + e.toString());
        }
    }

}

Notes:

• The methods for signing data are in the java.security package, so the program imports everything from that package. It also imports the java.io package since that package contains the methods needed to input the file data to be signed.

• A single argument is expected, specifying the data file to be signed.

• The code written in subsequent steps of this lesson will go between the try and catch blocks.

Generating and Verifying Signatures