/* 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());
}
