Network Security

1) To increase the key size of DES to 128 bits, Prof. Crypto decides to use two different keys: K1 and K2 each of size 64 bits. The Professor then encrypts each message twice once with K1 followed by K2. Will the attacker need to test out 2^128 keys in order to determine the keys using brute force or can the attacker determine the keys faster?. Justify your answer.

2) What will the output of a DES encryption algorithm be if the mangler function maps all its inputs to a zero.