简单加密/解密方法包装, 含encode(),decode(),md5()

package steeven;

/*
用途: 简单加密/解密方法包装
作者: [email protected]
日期: 12/05/2001
感谢: http://www-900.ibm.com/developerWorks/java/l-security/index.shtml

说明:
This Class need JCE, download here:
http://java.sun.com/security/index.html

*/

import java.security.*;
import javax.crypto.*;
public class Crypt {

  private static String Algorithm="DES"; //定义 加密算法,可用 DES,DESede,Blowfish

  static boolean debug = false;

  static{
    Security.addProvider(new com.sun.crypto.provider.SunJCE());
  }

  //生成密钥, 注意此步骤时间比较长
  public static byte[] getKey() throws Exception{
    KeyGenerator keygen = KeyGenerator.getInstance(Algorithm);
    SecretKey deskey = keygen.generateKey();
    if (debug)
      System.out.println("生成密钥:"+byte2hex(deskey.getEncoded()));
    return deskey.getEncoded();
  }

  //加密
  public static byte[] encode(byte[] input,byte[] key) throws Exception{
    SecretKey deskey = new javax.crypto.spec.SecretKeySpec(key,Algorithm);
    if (debug){
      System.out.println("加密前的二进串:"+byte2hex(input));
      System.out.println("加密前的字符串:"+new String(input));
    }
    Cipher c1 = Cipher.getInstance(Algorithm);
    c1.init(Cipher.ENCRYPT_MODE,deskey);
    byte[] cipherByte=c1.doFinal(input);
    if (debug)
      System.out.println("加密后的二进串:"+byte2hex(cipherByte));
    return cipherByte;
  }

  //解密
  public static byte[] decode(byte[] input,byte[] key) throws Exception{
    SecretKey deskey = new javax.crypto.spec.SecretKeySpec(key,Algorithm);
    if (debug)
      System.out.println("解密前的信息:"+byte2hex(input));
    Cipher c1 = Cipher.getInstance(Algorithm);
    c1.init(Cipher.DECRYPT_MODE,deskey);
    byte[] clearByte=c1.doFinal(input);
    if (debug){
      System.out.println("解密后的二进串:"+byte2hex(clearByte));
      System.out.println("解密后的字符串:"+(new String(clearByte)));
    }
    return clearByte;
  }

  //md5()信息摘要, 不可逆
  public static byte[] md5(byte[] input) throws Exception{
    java.security.MessageDigest alg=java.security.MessageDigest.getInstance("MD5"); //or "SHA-1"
    if (debug){
      System.out.println("摘要前的二进串:"+byte2hex(input));
      System.out.println("摘要前的字符串:"+new String(input));
    }
    alg.update(input);
    byte[] digest = alg.digest();
    if (debug)
      System.out.println("摘要后的二进串:"+byte2hex(digest));
    return digest;
  }

  //字节码转换成16进制字符串
  public static String byte2hex(byte[] b) {
    String hs="";
    String stmp="";
    for (int n=0;n<b.length;n++){
      stmp=(java.lang.Integer.toHexString(b[n] & 0XFF));
      if (stmp.length()==1)
        hs=hs+"0"+stmp;
      else hs=hs+stmp;
        if (n<b.length-1)  hs=hs+":";
      }
    return hs.toUpperCase();
  }

  public static void main(String[] args) throws Exception{
    debug = true;
//    byte[] key = getKey();
    byte[] key = "好好学习".getBytes();
    decode(encode("测试加密".getBytes(),key),key);
    md5("测试加密".getBytes());
  }
}

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