import javax.crypto.*;
/**
* 本例解釋如何利用DES私鑰加密算法加解密
*
* @author Devon
* @version 1.0 04/03/10
*/
public class SingleKeyExample {
public static void main(String[] args) {
try {
String algorithm = "DES"; //定義加密算法,可用 DES,DESede,Blowfish
String message = "Hello World. 這是待加密的信息";
// 生成個DES密鑰
KeyGenerator keyGenerator = KeyGenerator.getInstance(algorithm);
keyGenerator.init(56); //選擇DES算法,密鑰長度必須為56位
Key key = keyGenerator.generateKey(); //生成密鑰
// 生成Cipher對象
Cipher cipher = Cipher.getInstance("DES");
//用密鑰加密明文(message),生成密文(cipherText)
cipher.init(Cipher.ENCRYPT_MODE, key); //操作模式為加密(Cipher.ENCRYPT_MODE),key為密鑰
byte[] cipherText = cipher.doFinal(message.getBytes()); //得到加密後的字節數組
System.out.println("加密後的信息: " + new String(cipherText));
//用密鑰加密明文(plainText),生成密文(cipherByte)
cipher.init(Cipher.DECRYPT_MODE, key); //操作模式為解密,key為密鑰
byte[] sourceText = cipher.doFinal(cipherText); //獲得解密後字節數組
System.out.println("解密後的信息: " + new String(sourceText));
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
/**
* @author Devon
*/
import java.security.*;
import java.security.spec.*;
import javax.crypto.*;
public class PairKeyExample {
public static void main(String argv[]) {
try {
String algorithm = "RSA"; //定義加密算法,可用 DES,DESede,Blowfish
String message = "張三，妳好，我是李四";
//產生張三的密鑰對(keyPairZhang)
KeyPairGenerator keyGeneratorZhang =
KeyPairGenerator.getInstance(algorithm); //指定采用的算法
keyGeneratorZhang.initialize(1024); //指定密鑰長度為1024位
KeyPair keyPairZhang = keyGeneratorZhang.generateKeyPair(); //產生密鑰對
System.out.println("生成張三的公鑰對");
// 張三生成公鑰(publicKeyZhang)並發送給李四,這裏發送的是公鑰的數組字節
byte[] publicKeyZhangEncode = keyPairZhang.getPublic().getEncoded();
//通過網絡或磁盤等方式,把公鑰編碼傳送給李四
//李四接收到張三編碼後的公鑰,將其解碼
KeyFactory keyFacoryLi = KeyFactory.getInstance(algorithm); //得到KeyFactory對象
X509EncodedKeySpec x509KeySpec =
new X509EncodedKeySpec(publicKeyZhangEncode); //公鑰采用X.509編碼
PublicKey publicKeyZhang = keyFacoryLi.generatePublic(x509KeySpec); //將公鑰的KeySpec對象轉換為公鑰
System.out.println("李四成功解碼,得到張三的公鑰");
//李四用張三的公鑰加密信息，並發送給李四
Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding"); //得到Cipher對象
cipher.init(Cipher.ENCRYPT_MODE, publicKeyZhang); //用張三的公鑰初始化Cipher對象
byte[] cipherMessage = cipher.doFinal(message.getBytes()); //得到加密信息
System.out.println("加密後信息：" + new String(cipherMessage));
System.out.println("加密完成，發送給李四...");
//張三用自己的私鑰解密從李四處收到的信息
cipher.init(Cipher.DECRYPT_MODE, keyPairZhang.getPrivate()); //張三用其私鑰初始化Cipher對象
byte[] originalMessage = cipher.doFinal(cipherMessage); //得到解密後信息
System.out.println("張三收到信息，解密後為：" + new String(originalMessage));
} catch (Exception ex) {
ex.printStackTrace();
}
}
}