In an attack scenario, we assume that the attacker Oscar manages somehow to provide Alice with a few pieces of plaintext that she encrypts. Show how Oscar can break the affine cipher by using two pairs of plaintext-ciphertext, (x_1, y_1) and (x_2, y_2). What is the condition for choosing x_1 and x_2? Remark: In practice, such an assumption turns out to be valid for certain settings, e.g., encryption by Web servers, etc. This attack scenario is, thus, very important and is denoted as a chosen plaintext attack