csharp md5 hash bouncycastle encypt decrypt with key

                
                        using SystemX = System.Security.Cryptography;
public static string Md5(string data)        {            
  var text = data;            
  using (var md5 = SystemX.MD5.Create())
  {                var bs = md5.ComputeHash(Encoding.UTF8.GetBytes(text)); 
   return BitConverter.ToString(bs).Replace("-", "").ToLower();           
  }       
}