An interesting topic for a startup is the publication of news, for example, about some events or local people (or ad texts, or resumes, or vacancies), compiled in such a way that certain characters are in certain positions of the text. And the set of these characters is the key or ciphertext. In fact, not only the decoding of the cipher becomes a problem, but the very fact of its discovery. This is something like a public encrypted text broadcast. And, if the full text of the message is made up of several publications in different publications (websites), then the detection and "hacking" of such messages and answers is a big problem. It remains, perhaps, to track the activity of publication sources ... Well, or ...