simpleexample.java

密码学中的JAVA例子

import  java.security.*;
import javax.crypto.*;

public class SimpleExample
{
 public static void main(String[] args) throws Exception
{
  if (args.length!=1){
      System.out.println("Usage: java SimpleExample text");
      System.exit(1);
}
String  text=args[0];
System.out.println("Generate a DESede key….");
KeyGenerator keyGenerator= KeyGenerator.getInstance("DESede");
keyGenerator.init(168);
Key key= keyGenerator.generateKey();
System.out.println("done generating the key.");
//create a cipher using that key to initialize it
Cipher cipher= Cipher.getInstance("Desede/ECB/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, key);
byte[]  plaintext =text.getBytes("UTF8");
//print out the bytes of the plaintext
System.out.println("\n plaintext:");
for (int i=0;i<plaintext.length;i++) {
  System.out.print(plaintext[i]+" ");
}
//perform the actual encryption
  byte[] ciphertext=cipher.doFinal(plaintext);
//print out the ciphertext
System.out.println("\n\nCiphertext: ");
for (int i=0;i<plaintext.length;i++) {
  System.out.print(plaintext[i]+" ");
}
//re-initialize the cipher to decrypt mode
cipher.init(Cipher.DECRYPT_MODE, key);
//perform the decryption
byte[] decryptedText=cipher.doFinal(ciphertext);
String  output =new String(decryptedText ,"UTF8");
System.out.println("\n\nDecrypted text: "+output);
}
}