Decrypt the following ciphertext which was encrypted by the above stream cipher: WRTCNRLDSAFARWKXFTXCZRNHNYPDTZUUKMPLUSOXNEUDOKLXRMCBKGRCCURR

1.30 We describe another stream cipher, which incorporates one of the ideas from the "Enigma" system used by Germany in World War II. Suppose that is a fixed permutation of Z-26. The key is an element K E Z26. For all integers i 2 1 the keystream element zi E Z26 is defined according to the rule z = (K + 1) mod 26. Encryption and decryption are performed using the permutations and T', respectively, as follows: ez(r)- T(z) + z mod 26 and d,(y) = -1 (y-z mod 26), where z E Z 26- Suppose that is the following permutation of 226: 0123 4567|891011 12 r(x)| 2313 24 071514 6 25 16|22| 119 13 | 14| 15 | 1617| 18|19 | 202122 2324 | 25 r(x)| 18511172121|1220410| 93 8 The following ciphertext has been encrypted using this stream cipher; use exhaus- tive key search to decrypt it: WRTCNRLDSAFARWKXFTXCZRNHNYPDTZUUKMPLUSOXNEUDO KLXRMCBKGRCCURR