Two subjects are examined in Chapters 16 and 17, bank secrecy and derivatives. Bank secrecy seems a simple subject, but it is difficult. Derivatives seem difficult, but, from the point of view of contractual law, they are simple. A contract providing that if the value of a basket of securities on the stock exchange goes over 100, the party will pay the counterparty the difference, is elementary. From the legal point of view, its technology is basic. It is simple compared to an offtake agreement with an electricity power station, a construction agreement for a refinery, or a financial lease of an aircraft.