HMAC.java

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import java.io.UnsupportedEncodingException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.util.*;

public class HMAC {

  public static void main(String[] args) throws Exception 
  {
	System.out.println("Enter message to get the sha 1 key:");
	Scanner sc=new Scanner(System.in);
	String msg=sc.nextLine();
	System.out.println("key is: "+hmacDigest(msg,"key","HmacSHA1"));
  }

  public static String hmacDigest(String msg, String keyString, String algo) {
    String digest = null;
    try {
      SecretKeySpec key = new SecretKeySpec((keyString).getBytes("UTF-8"), algo);
      Mac mac = Mac.getInstance(algo);
      mac.init(key);

      byte[] bytes = mac.doFinal(msg.getBytes("ASCII"));

      StringBuffer hash = new StringBuffer();
      for (int i = 0; i < bytes.length; i++) {
        String hex = Integer.toHexString(0xFF & bytes[i]);
        if (hex.length() == 1) {
          hash.append('0');
        }
        hash.append(hex);
      }
      digest = hash.toString();
    } catch (UnsupportedEncodingException e) {
    } catch (InvalidKeyException e) {
    } catch (NoSuchAlgorithmException e) {
    }
    return digest;
  }
}