一次性密码(OTP)C#到Java转换代码

这是我去年写的代码:(我知道这个OTP的安全性很低,但我不需要防弹的代码)

SHA1CryptoServiceProvider hash = new SHA1CryptoServiceProvider(); //first hash with sha1
byte[] hashPass = hash.ComputeHash(Encoding.ASCII.GetBytes(pass)); //pass is entered by user
HMACMD5 hma = new HMACMD5(hashPass); // use the hashed value as a key to hmac
OTPass = hma.ComputeHash(Encoding.ASCII.GetBytes(email + Counter(email)));// generate OTPass,Counter(email) is the counter of the user taken from database
increaseCounter(email); // updating the counter
this.SetLog(this.GetLog() + Environment.NewLine + "OTPass Generated: " + BitConverter.ToString(OTPass)); // OTP

这是我试图将C#转换为的Java代码:(这只是SHA1部分,我找不到如何用Java编写HMAC-MD5)

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

public class otp {

/**
 * @param args
 * @throws IOException 
 */
public static void main(String[] args) throws IOException {

    System.out.println("Please enter your username:");
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    String username = br.readLine();
    System.out.println("Please enter your password:");
    String password = br.readLine();

    try {
         MessageDigest md = MessageDigest.getInstance("SHA1");

         String input = password;
         md.update(input.getBytes()); 
         byte[] output = md.digest();
         System.out.println();
         System.out.println("SHA1(""+input+"") =");
         System.out.println("   "+bytesToHex(output));


      } catch (Exception e) {
         System.out.println("Exception: "+e);
      }
   }
   public static String bytesToHex(byte[] b) {
      char hexDigit[] = {'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};
      StringBuffer buf = new StringBuffer();
      for (int j=0; j<b.length; j++) {
         buf.append(hexDigit[(b[j] >> 4) & 0x0f]);
         buf.append(hexDigit[b[j] & 0x0f]);
      }
      return buf.toString();        
}
}

感谢帮助