(a) wr rh ru qrw wr eh wkdw fv wkh txhvwlrq

(b) fsesn roffe ocaey sooar uonve aurts rrdea greh

(c) jbm udshzljcku yx frgtiu rojalmqnqqxk glvx ua vrw qpvby avbmqknhy wh k joeweg xgbeiktjcwp kjs fy vovfkesemqf qozgfktdwm kx lvv tdutacag fy qfoqbahyfi yarouwrebs wh cgfkbda inqgfzmxga yraqy hfyzcdw ce kqhlqw hsifknivsgbj lkjxqcw tfk uriozds kaqn eg kjs llyho seaqblufmed s qfnicv qp iizvamwtd lc jxbykv k joeweg mnoesem ez i tkfrff fyzoelokbeh ywsuyjxbykv gazc iulnqbe o gthnqcv kcim eh bjo sfito ua kd hoimynqqxk hyx qlzci sqthhxqpq lc kau jqxyl vvgsy i rojalmqnqqx owce ry tgck rzlellgbwr ryjyz seaqblufmed zoj uuyv rojtfkcyl vrw odhkhb qp vwjhhxmt dzok kugikxk arr ry ipkdmjxt qqvr ysexhubkxy tlgsnqqxk hyxiy ogxwfrmyho hefqkbeha fohsew yh i hefrrfuhbcv oop hd npg qwbvkqnqpq xievjcwpc gt itdxwo zwfdnjubkyf gktjcavsug yxdwm kd ag fy lcbcv aaghhnipmw hf vegxwdw hyxiy ogxwfrmyho hefqkbeha

Problem 2. Vigenere is associated with the autokey method of generating long keys for enciphering using the Vigenere table. In the standard Vigenere method the key is a repeated phrase placed above the text, e.g.,

Key: KING KING KING KING

Plaintext: HERE ISTH EMES SAGE

Ciphertext: RMEK SAGN OURY CITK

and then the key letter above each plain text letter is used to perform a Caesar shift by that amount. There are two versions of the auto key method. In the first, after using the key phrase to start the enciphering, one uses the plaintext as the running key, e.g.,

Key: KING HERE ISTH EMES

Plaintext: HERE ISTH EMES SAGE

Ciphertext: RMEK PWKL MEXZ WMKW

In the second method, after using the key to start, one uses the ciphertext as the running key, e.g.,

Key: KING RMEK ZEXR DQBJ

Plaintext: HERE ISTH EMES SAGE

Ciphtertext: RMEK ZEXR DQBJ VQHN

One of these two methods is much more secure than the other. Which one and why? The following text was enciphered using the first autokey method. Given that the plaintext word CIPHER appears somewhere in the text can you decipher it?

MSKF AGWQ FQHR LELM DVQK ZJMG ZEIW PISS TWSJ MGZ

Problem 3. Two of the following three ciphertexts were created using the ordinary Vigenere method with the same keyword. Which two do you think and why? (Bonus: break the ciphers and find their source.)

Ciphertext 1: osgzstmqrmsmpszcilcsdqltcswjuiwaclebpxtsqlqrvymslusgzqkwyilavdlmvxlgvwzxbhzoqhmzlbuwomiosukarefhrzmzxavhenvhrs

Ciphertext 2: tdcadiictsosmpvyoobcinluksxltweahjwplsqhpyyoejgueyoafrjqaweesoxteoxhfrlapwoswezbwujryprkhcifybjsbolmlwhimdpajb

Ciphertext 3: hmzlbhjqgbwvhjuwttswzahhmsqudciawqympiooewfmvasalncnzwqymwxywhkajwptiwdigjohkmvvpdkwdwuhghvarmosowfxxygrxmoxfk

Problem 4. Consider a monoalphabetic substitution cipher that chooses a random permutation of the alphabet in which a letter never gets mapped to itself. Is this more secure, less secure or of the same security as a random monoalphabetic substitution cipher. If different, estimate the difference in security of the two approaches by estimating the unicity distance of each. In practice is there much difference?

Problem 5. Do you observe an awkwardness or weirdness, in wording, of a problem you are reading now? If possible, respond in kind.

Report problems to dkrizanc at wesleyan dot edu