The key is 7

Question 1: Eve is given the ciphertext 'ECLEHLPQNGYPLLPALIETQDUWQRFAIOAULPQVGLHDEWVEFQLEVEFQ and the information that the plaintext is in English and encrypted with the 26-character multiplicative cipher. This is a - Apply frequency analysis to the ciphertext and find the key k. a) Use the table above of plaintext-ciphertext pairs to decipher the message in a) and find the plaintext. [2 marks] Number Cipher Text Encryphon Plain Eipher Text Symbal with key 7 20 21 22 (20x15) mod 26=14 (21x15) mod 26=3 (22415) mod 26= 18 (23*15) mod 26= 7 (auxis) mod 26=22 (2581) mod 26= 11 bau I 3 J H Y Z 24 23 2 Number Encryption Cipher Text 0 A B C D E F G tam & noit oon ood Cipher text with key 7 Symbol (0x15)1-26 =D A P (1415)126-15 (2x15) 726 - 4 4 T (3x15) %.26 = 19 I (4x15) 1. 26 = 8 (SX15)1.26 =23 (6x15) 4.26 = 12 (7415) 7.26 = 1 B (&xls) 1.26 = 16 (9415)1-26=5 (10x15) 4.26= 20 U (1815) 4-26= 9 (12815)1.26 =24 Y (13X13) 1.26 = 13 (14815) 7.26=2 (15815) 1 26 - 17 R (16x15) % 26= 6 (1915) 1.26 =21 (1815) 1.26 = 10 K (19X13) 7.26 = 25 I HEMP o 3 xH4top L M M N C N 0 P Q R 14 15 16 17 18 Taud 5>XN S. T 19