code: private static byte[] hexStringToByteArray(String s)
  	{
  		byte[] b = new byte[s.length() / 2];
  		for (int i = 0; i < b.length; i++)
  		{
  			int index = i * 2;
  			int v = Integer.parseInt(s.substring(index, index + 2), 16);
  			b[i] = (byte) v;
  		}
  		return b;
  	}
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