2.9. Given is a stream cipher which uses a single LFSR as key stream generator. The LFSR has a degree of 256. 1. How many plaintext/ciphertext bit pairs are needed to launch a successful attack? 2. Describe all steps of the attack in detail and develop the formulae that need to be solved. 3. What is the key in this system? Why doesn't it make sense to use the initial contents of the LFSR as the key or as part of the key