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Unformatted text preview: CMPT 404 Cryptography and Protocols Spring 2012 Exercises on Probability and Perfect Security. Due: Thursday, February 2nd (at the beginning of the class) Reminder: the work you submit must be your own. Any collaboration and consulting outside resources must be explicitly mentioned on your submission. 1. The following text was encrypted using a substitution cipher. Find the plaintext and explain the steps you took to find it. Punctuation marks are removed from the text. Tables of English letters frequencies can be found on the web. GHDG XLBHSFH IHBB LS YKH CLGGBH TI D OTWG TZY OHSY DBB BLJKYX YKH ILWH BHDUHG ZU LS EBDFA XCTAHX DXKHX DSG FLSGHWX OHWH LS YKH HQHX TI YKH GODWNHX DSG YKH OTTG ODX ILBBHG DJDLS OLYK YKHLW FBDCTZW DSG YKHLW FWLHX ELBET ITZSG KLCXHBI WZSSLSJ WTZSG DSG WTZSG DX KH YKTZJKY DSG FDBBLSJ DSG FDBBLSJ GTWL STWL TWL TLS JBTLS ILBL ALBL ETCEZW ETIZW GODBLS EDBLS YKTWLS TDAHSXKLHBG OKLBH UHTUBH KH FTZBG STY XHH TW IHHB OHWH GTLSJ YKH XDCH DBB WTZSG KLC OLYK DS TFFDXLTSDB ELBET YKWTOS LS EZY YKH FWLHX TI YKH TYKHWX JTY XYHDGLBQ IZWYKHW DSG IDLSYHW DSG YKTZJK DIYHW D OKLBH LY XHHCHG YT KLC YKHQ FKDSJHG YT QHBBX DSG FWLHX ITW KHBU LS YKH GLXYDSFH DBB STLXH DY BDXY GLHG WLJKY DODQ DSG KH ODX BHIY DBTSH LS FTCUBHYH XLBHSFH DSG GDWASHXX...
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- Spring '12