package rsa;
/*
* SHA1WithRSA:用SHA算法进行签名，用RSA算法进行加密
* 发送端的签名及对签名的加密，接收端的解密与验证签名
*/
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 RSA_Demo {
RSA_Demo() {
init();
}
private void init() {
prepare();
doSenderWork();
doReceiverWork();
}
// share by sender and receiver
Signature sign = null;
// belong to sender,it visible to sender and receiver
PublicKey publicKey = null;
// belong to sender,it is only visible to sender
PrivateKey privateKey;
private void prepare() {
KeyPairGenerator keyGen = null;
try {
// 实例化一个RSA算法的公钥/私钥对生成器
keyGen = KeyPairGenerator.getInstance("RSA");
} 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 {
// 实例化一个用SHA算法进行散列，用RSA算法进行加密的Signature.
sign = Signature.getInstance("SHA1WithRSA");
} catch (NoSuchAlgorithmException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
void doSenderWork() {
String words = "This is robin.How are you?";
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");
}
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;
}
}
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