Начиная с того, что это реальный вполне себе production-grade шифр, который был придуман Брюсом Шнайером для книжки "Криптономикон" Нила Стивенсона
In 1999 Paul Crowley discovered that there is a bias towards repeating characters in the keystream, which occur about every 1/22.5 characters rather than the expected 1/26.[2] As a result, Solitaire leaks information at a rate of about 0.0005 bits per character.[3] While its security may perhaps be adequate for very short messages, in general Solitaire is considered insecure.