COMP 133 - Assignment 2 |
Problem 1. The following two ciphertexts were encoded using the same keyword column transposition cipher. What is the length of the keyword used? What is the source of the two plaintexts?
Ciphertext 1: irhsremihheniheneysehecreitnemvepanvdttttgeebename
Ciphertext 2: irhaontleeeniitfygachecreornhivepshepabttgeemdcipt
Problem 2. The following ciphertext was encoded using a Viginere cipher. What is length of the keyword used? What is the source of the plaintext?
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 3. In order to make things more difficult for Eve, Alice and Bob decide to perform a double encryption as follows: First, they encrypt the plaintext using a Caesar shift and then they encrypt the resulting ciphertext using a monoalphabetic substitution cipher. Is this system more secure, less secure or about the same as a single encryption using a monoalphabetic substitution cipher? Explain your answer.
Problem 4. 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
There are two versions of the auto key method. In the first, after using the key 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?
Problem 5. Compose a paragraph (as long and as funny as you possibly can make up) which makes sense and avoids using any of a given symbol which is conspicuously missing from a problem you are reading now.
Bonus. Create an (hopefully amusing or apt) anagram using your name or a variation on your name or a nickname. For example, my full name is David Daniel Martin Krizanc and if you let me cheat a little and use D. Dany Krizanc I can get CRAZY AND KIND. If you can come up with something better for me I would be interested as well.
| Report problems to dkrizanc at wesleyan dot edu
|