Document from the year 2016 in the subject Mathematics - Number Theory, grade: 1,7, Free University of Berlin (Fachbereich für Mathematik und Informatik), course: Kryptografie Seminar, language: English, abstract: In this discourse, I introduce the reader to the concept of Chosen-Plaintext Attacks, by first defining them and then introducing to some of the properties of encryption schemes secure against Chosen-Plaintext attacks. I then introduce the concept of pseudorandom functions and try to show, how pseudorandom functions or permutations help understanding CPA-security. The discourse ends with constructing a CPA-secure encryption scheme based on pseudorandom permutations and a proposition that proves its correctness.