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{            /* Generate a key pair */            KeyPairGenerator keyGen = KeyPairGenerator.getInstance("DSA", "SUN");            SecureRandom random = SecureRandom.getInstance("SHA1PRNG", "SUN");            keyGen.initialize(1024, random);            KeyPair pair = keyGen.generateKeyPair();            PrivateKey priv = pair.getPrivate();            PublicKey pub = pair.getPublic();            /* Create a Signature object and initialize it with the private key */            Signature dsa = Signature.getInstance("SHA1withDSA", "SUN");             dsa.initSign(priv);            /* Update and sign the data */            FileInputStream fis = new FileInputStream(args[0]);            BufferedInputStream bufin = new BufferedInputStream(fis);            byte[] buffer = new byte[1024];            int len;            while (bufin.available() != 0) {                len = bufin.read(buffer);                dsa.update(buffer, 0, len);                };            bufin.close();            /* Now that all the data to be signed has been read in,                     generate a signature for it */            byte[] realSig = dsa.sign();                    /* Save the signature in a file */            FileOutputStream sigfos = new FileOutputStream("sig");            sigfos.write(realSig);            sigfos.close();            /* Save the public key in a file */            byte[] key = pub.getEncoded();            FileOutputStream keyfos = new FileOutputStream("suepk");            keyfos.write(key);            keyfos.close();        } catch (Exception e) {            System.err.println("Caught exception " + e.toString());        }    };}