There are 26 capital letters A through Z in the alphabet. There are ten digits 0 through 9. For Marpx Privacy™ Level Three, that means that there are 26 + 10 = 36 choices for each of the seven characters in a key. 36 X 36 X 36 X 36 X 36 X 36 X 36 works out to 78 billion different keys. Whose data is worth that much effort to disclose? Maybe that of a terrorist cell that is planning serious harm. Can a terrorist message be cracked? Yes, but at great expense. Not many organizations in the world have the computer power to decrypt streams of files and messages, each with different keys.
So there is a front door to decrypting content encrypted with Marpx Privacy™ Level Three. The only question is whether the content is worth the enormous time and effort required. Example: If all you are sharing in your encrypted communication is your firm's design of a new product, you are probably more than secure. In the really exceptional case that China's People's Liberation Army really wants your stuff, appeal for sponsorship to Extreme Encryption by a government agency with security concerns.