md5.java

这是一个用Java实现ElGamal加密解密和签名验证的算法

/*
 * MD5 Hashing Class and Method
 *
 * @author Ge ZHANG (2937207)
 * @login name: gz847
 * @version 1.00 07/08/11*/

import java.util.*;
import java.io.*;
import java.security.*;

public class MD5{

 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;
  }
 }
}