●●●●● ●●●● ●●0 Example Cryptanalysis ●●● ●●●● given ciphertext UZQSOVUOHXMOPVGPOZPEVSGZWSZOPFPESXUDBMETSXAIZ VUEPHZHMDZSHZOWSFPAPPDTSVPQUZWYMXUZUHSX EPYEPOPDZSZUF POMBZWPFUPZHMDJUDTMOHMQ count relative letter frequencies ●P:13.33%,z:11.67%,S:8.33%,U:8.33%,O:7.5%,M:6.67%,etc · guess P& Z are e and t It's helpful to look at frequency of two-letter combinations. The most common is th ● guess Zw is th proceeding with trial and error finally get it was disclosed yesterday that several informal but direct contacts have been made with political representatives of the viet cong in moscow COMP4690. HKBUCOMP4690, HKBU 17 Example Cryptanalysis ⚫ given ciphertext: UZQSOVUOHXMOPVGPOZPEVSGZWSZOPFPESXUDBMETSXAIZ VUEPHZHMDZSHZOWSFPAPPDTSVPQUZWYMXUZUHSX EPYEPOPDZSZUFPOMBZWPFUPZHMDJUDTMOHMQ ⚫ count relative letter frequencies ⚫ P: 13.33%, Z: 11.67%, S: 8.33%, U: 8.33%, O: 7.5%, M: 6.67%, etc. ⚫ guess P & Z are e and t ⚫ It’s helpful to look at frequency of two-letter combinations. The most common is “th”. ⚫ guess ZW is th ⚫ proceeding with trial and error finally get: it was disclosed yesterday that several informal but direct contacts have been made with political representatives of the viet cong in moscow