Assignment 2

Due Tuesday, July 3, in class

Recommended reading: Stallings, Chapter 2

1. (10 points) Solve the following substitution cipher:

   
   MSN GL DWMVC DTAN, OYTWW SRY XKTYYTSQ,
   
   	OYTWW TO OTYYTSQ, OYTWW TO OTYYTSQ 
   
   RS YIMY JMWWTN DKOY -- OYTWW ZWTYYTSQ
   
   	YIARKQI GL NRWRARKO NRGMTS; 
   
   DKY TY VMSSRY OYRJ ZARG QMUTSQ
   
   	ZRA TY YAKWL ZTSNO MGMUTSQ 
   
   YIMY, DL MAYZKW JMAMJIAMOTSQ,
   
   	T OKVI AILGTSQ VMS OKOYMTS -- 
   
   SRYBTYIOYMSNTSQ GL WROY OLGDRW
   
   	T OKVI AILGTSQ OYTWW OKOYMTS -- 
   
   YIRKQI T OIMS'Y YAL TY MQMTS!
   
    - MAYIKA QRANRS JLG
   
   
   (ZARG "M PRTN", MNMTA'O YAMSOWMYTRS RZ
   
    JHAHV'O "WM NTOJMATYTRS")
   

   Write a few sentences about what letters you got first, what wrong turns you took, what made it easy or hard, or any other observations. (Note that, as usual, capitalization is not indicated in the cryptogram.)
2. (5 points) Problem 2.2 from the Stallings book
3. (10 points) Problem 2.5
4. (5 points) Problem 2.8 (see pp. 33-34)
5. (25 points) People often generate a permutation of the alphabet by using a keyword or keyphrase. For example, the permutation in problem 2.7 is generated from the keyword CIPHER. Sometimes people start in the middle of the alphabet, as in this permutation based on "Leo Irakliotis" (with repeated letters removed):

   plain:    a b c d e f g h i j k l m n o p q r s t u v w x y z
   cipher:   N P Q U V W X Y Z L E O I R A K T S B C D F G H J M   
   

   The cipher in problem 2.5 is another variation on this theme.

   What are the advantages of using such a permutation? What are the disadvantages? How do these issues relate to people's choices of passwords and passphrases?

   (Your answer should be roughly one page. Try to be quantitative where you can.)