java加密、解密

简单demo:

import java.security.*;
 import java.security.spec.*;

 class MD5_test {
  public final static String MD5(String s) {
   char hexDigits[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
     'a', 'b', 'c', 'd', 'e', 'f' };
   try {
    byte[] strTemp = s.getBytes();
    MessageDigest mdTemp = MessageDigest.getInstance("MD5");
   mdTemp.update(strTemp);
    byte[] md = mdTemp.digest();
    int j = md.length;
    char str[] = new char[j * 2];
    int k = 0;
    for (int i = 0; i < j; i++) {
     byte byte0 = md[i];
     str[k++] = hexDigits[byte0 >>> 4 & 0xf];
     str[k++] = hexDigits[byte0 & 0xf];
   }
    return new String(str);
   } catch (Exception e) {
    return null;
  }
 }

  public static void main(String[] args) {
   // MD5_Test aa = new MD5_Test();
   System.out.print(MD5_test.MD5("b"));
 }
 }

import java.security.MessageDigest;


 public class MD5andKL {
  // MD5加码。32位
  public static String MD5(String inStr) {
   MessageDigest md5 = null;
   try {
    md5 = MessageDigest.getInstance("MD5");
   } catch (Exception e) {
   System.out.println(e.toString());
   e.printStackTrace();
    return "";
  }
   char[] charArray = inStr.toCharArray();
   byte[] byteArray = new byte[charArray.length];

   for (int i = 0; i < charArray.length; i++)
    byteArray[i] = (byte) charArray[i];

   byte[] md5Bytes = md5.digest(byteArray);

   StringBuffer hexValue = new StringBuffer();

   for (int i = 0; i < md5Bytes.length; i++) {
    int val = ((int) md5Bytes[i]) & 0xff;
    if (val < 16)
     hexValue.append("0");
   hexValue.append(Integer.toHexString(val));
  }

   return hexValue.toString();
 }

  // 可逆的加密算法
  public static String KL(String inStr) {
   // String s = new String(inStr);
   char[] a = inStr.toCharArray();
   for (int i = 0; i < a.length; i++) {
    a[i] = (char) (a[i] ^ 't');
  }
   String s = new String(a);
   return s;
 }

  // 加密后解密
  public static String JM(String inStr) {
   char[] a = inStr.toCharArray();
   for (int i = 0; i < a.length; i++) {
    a[i] = (char) (a[i] ^ 't');
  }
   String k = new String(a);
   return k;
 }

  // 测试主函数
  public static void main(String args[]) {
   String s = new String("a");
   System.out.println("原始：" + s);
   System.out.println("MD5后：" + MD5(s));
   System.out.println("MD5后再加密：" + KL(MD5(s)));
   System.out.println("解密为MD5后的：" + JM(KL(MD5(s))));
 }
 }