Consider a Feistel cipher composed of 16 rounds with block length 128 bits and key length 128 bits. Suppose that, for a given k, the key scheduling algorithm determines values for the first eight round keys, k1, k2, . . ., k8, and then sets k9 = k8, k10 = k7, k11 = k6, . . ., k16 = k1 Suppose you have a ciphertext c. Explain how, with access to an encryption oracle, you can decrypt c and determine m using just a single oracle query. This shows that such a cipher is vulnerable to a chosen plaintext attack. (An encryption oracle can be thought of as a device that, when given a plaintext, returns the corresponding ciphertext. The internal details of the device are not known to you, and you cannot break open the device. You can only gain information from the oracle by making queries to it and observing its responses.)

3. ranga ramasesh is the operations manager for a firm that is trying to decide which one of four countries it should research for possible outsourcing providers. the first step is to select a country based on cultural risk factors, which are critical to eventual business success with the provider. ranga has reviewed outsourcing provider directories and found that the four countries in the table that follows have an ample number of providers from which they can choose. to aid in the country selection step, he has enlisted the aid of a cultural expert, john wang, who has provided ratings of the various criteria in the table. the resulting ratings are on a 1 to 10 scale, where 1 is a low risk and 10 is a high risk. john has also determined six criteria weightins: trust, with a weight of 0.3; quality, with 0.2; religious, with 0.1; individualism, with 0.2; time, with 0.1; and uncertainity, with 0.1. using the factor-rating method, which country should ranga select? why? (2 points)