public HmacHelper(Config config)
	{
		channel = new Base64Channel();
		File hKey = new File(config.getString("hmac.key"));
		if(hKey.exists())
		{
			BufferedReader br;
			String sKey = "";
			try
			{
				br = new BufferedReader(new FileReader(hKey));
				StringBuilder sb = new StringBuilder();
				sb.append(br.readLine());
				sKey = sb.toString();
				br.close();
			} 
			catch (FileNotFoundException e)
			{
				// TODO Auto-generated catch block
				e.printStackTrace();
			} 
			catch (IOException e)
			{
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			key = new SecretKeySpec(sKey.getBytes(), "HmacSHA256");
			try
			{
				hMac = Mac.getInstance("HmacSHA256");
				hMac.reset();
				hMac.init(key);
				
			} 
			catch (NoSuchAlgorithmException e)
			{
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (InvalidKeyException e)
			{
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		else
		{
			throw new IllegalArgumentException("File not found.");
		}
	}