import java.security.InvalidKeyException;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.Signature;
import java.security.SignatureException;
public class DSA_Demo {
DSA_Demo()
{
init();
}
private void init()
{
prepare();
doSenderWork();
doReceiverWork();
}
//share by sender and receiver
Signature
sign;
//belong to sender,it visible to sender and receiver
PublicKey
publicKey;
//belong to sender,it is only visible to sender
PrivateKey
privateKey;
private void prepare()
{
KeyPairGenerator keyGen=null;
try {
//实例化一个DSA算法的公钥/私钥对生成器
keyGen=KeyPairGenerator.getInstance("
DSA");
}
catch (NoSuchAlgorithmException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
int keysize=1024;
//设置公钥/私钥对的长度
keyGen.initialize(keysize);
//生成一个RSA算法的公钥/私钥
KeyPair keyPair=keyGen.generateKeyPair();
privateKey=keyPair.getPrivate();
publicKey=keyPair.getPublic();
try {
//实例化一个DSA签名算法的Signature.
sign=Signature.getInstance("
DSA");
}
catch (NoSuchAlgorithmException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
void doSenderWork()
{
String words="This is robin.How are you?This a DSA Signature Demo";
Message msg=new Message(words.getBytes());
try {
//设置加密散列码用的私钥
sign.initSign(privateKey);
}
catch (InvalidKeyException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
//设置散列算法的输入
sign.update(msg.getBody());
}
catch (SignatureException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
byte data[]=null;
try {
//进行散列，对产生的散列码进行加密并返回
data=sign.sign();
}
catch (SignatureException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
//把加密后散列（即签名）加到消息中
msg.setSignature(data);
//发送消息
sendMsg(msg);
}
Message sendingMsg;
void sendMsg(Message sendMsg)
{
sendingMsg=sendMsg;
System.out.println("sending Message Signed by DSA");
}
void doReceiverWork()
{
//收到消息
Message msg=getReceivedMsg();
try {
//设置解密散列码用的公钥。
sign.initVerify(publicKey);
}
catch (InvalidKeyException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
try {
//设置散列算法的输入
sign.update(msg.getBody());
}
catch (SignatureException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
/*进行散列计算，比较计算所得散列码是否和解密的散列码是否一致。
* 一致则验证成功，否则失败
*/
if(
sign.verify(msg.getSignature()))
{
System.out.println("数字签名验证成功！");
}
else
{
System.out.println("数字签名验证失败！");
}
}
catch (SignatureException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
Message getReceivedMsg()
{
System.out.println("receiving Message");
return sendingMsg;
}
}
class Message
{
private byte [] body;
private byte [] signature;
Message(
byte data[])
{
body=data;
}
byte[] getBody()
{
return body;
}
byte[] getSignature()
{
return signature;
}
void setSignature(
byte data[])
{
signature=data;
}
}
