Armchair Cryptanalysis

Due: Wednesday, Febuary 16

General Instructions. Students are required to work in groups of 2 or 3 for this assignment. An assignment submitted on behalf of a "group" having only one student will receive a grade of F. All members of the group are responsible for understanding the entire assignment.

No late assignments will be accepted.

Academic Integrity. Collaboration between groups is prohibited and will be treated as a serious violation of the University's academic integrity code.

The Assignment. Choose and submit a solution for only one of the following cipher-breaking exercises. In each, you are given enciphered English text and a hint about the encryption algorithm that was used. Your mission: Develop (or find on the web) the necessary (software) tools. Then, use them to help you produce plaintext.

Grading. The exercises that follow appear in increasing order of difficulty--the first is the easiest and the last is the most difficult. Which (single) exercise you submit determines your grade on this assignment. (Try as many of the exercises as you like, but hand-in only one.)

U (Unsatisfactory) Submitted work is not indicative of a "good faith" attempt to solve any exercise.
GF (Good Faith Attempt) Submitted work is indicative of a "good faith" attempt to solve one of the exercises.
G (Good) The correct plaintext for exercise 1 was derived, and the manner in which it was derived is cryptoanalytically justified (i.e., guessing is not good enough) and adequately documented.
B (Better) The correct plaintext for exercise 2 was derived, and the manner in which it was derived is cryptoanalytically justified (i.e., guessing is not good enough) and adequately documented.
VG (Very Good) The correct plaintext for exercise 3 was derived, and the manner in which it was derived is cryptoanalytically justified (i.e., guessing is not good enough) and adequately documented.
E (Excellent) The correct plaintext for exercise 4 was derived, and the manner in which it was derived is cryptoanalytically justified (i.e., guessing is not good enough) and adequately documented.

Exercise 1

The text was enciphered using a monoalphabetic substitution cipher. Blank spaces and punctuation have not been altered.

gqnpn ch m pnampdmtjl ejzhn xmpmjjnj tngunno gqn xpztjnah zk gqn
xqlhcechg moy gqzhn zk gqn eplxgzspmxqnp.  gqn hlhgna zo uqceq m
anhmsn ch noecxqnpny ezppnhxzoyh gz gqn jmuh zk gqn vocbnphn, gqn
cognpenxgny anhhmsnh gz gqn nbcynoen mbmcjmtjn, gqn dnlh kzp m yml zp
m anhhmsn gz caxzpgmog ezohgmogh uqceq qmbn gz tn yngnpacony. gqn
ezppnhxzoynoen ch bnpl ejzhn, tvg gqn hvtineg amggnp zk eplxgzspmxql
ch bnpl nmhcjl ynmjg ucgq tl ychepngn ameqconpl, xqlhceh ozg hz
nmhcjl.  mjmo gvpcos.

Exercise 2

The text was enciphered using a monoalphabetic substitution cipher. Blank spaces were first deleted and then inserted at convenient locations.
ewuue lzyih nojcl jkwuk wcyio jcljl aujyi uwcxi dmljo oukuo wcbwc
wuv.y cykkw xcrlc ubojm ovkun yuswe erwcw rwtlc owkly cfgjo fdily
rojlg lyilb depwi wcwuv .unln vfjox lcfox ycfun liomy euiyu kwflm
vkwfl wcunl yjroj vkyu. comof vunod xnymo dubdk wocoj bwkkw oc,lp
ljvoc lkgoh lobun lwjgl yilwr lrwkk woc,u weeko rlmof viyrl ycfog
lclfu nlfoo j.unl jlunl vsljl ,wcyc ldujo cbox, unlif joxlc iyuyc
funln vmyeu fox;u nlvrd knjoo rlfdg swuny uljjw meljo yj.yc fcomo
fvclp ljsyk unljl coroj l.

Exercise 3

The text was enciphered using a polyalphabetic substitution cipher, where the key length is 3. Blank spaces were first deleted and then inserted at convenient locations.
furwq mhqaz udqpt zuddv bqmwd blnpt uf.Ob tnrtf mndbx qgmqw cqrrq
t,zui qbrdd v,omj ebqar tbk,i torsf lzpaz bonwq bjhsx tagpi qdxqn
gjalu opqqm ohtbu nxbsn ,hwam mqbjv bgaxq ddcvz nhtnm tqptj kgoha
grngf tfmqp ggoom jmwqu cbuat mtnaf moadn icnrq dgxga dnabo nqmdd
ctu;l furwa d,hsg daxec dnatu mxblz usffg ovtdr wtbqu udttl ,kwtf
tohtf qkwm- kfsxp gfznq dtgno pamvh tjmwq ogpkg ohrwq nirzp taxec
qdqgp tdbow gkqnc wqmep sohaa qatmt jmwqr tpazn qmdfs gtcgd dxeht
bkn;l ohgpt ,delz qbctg fbtpu qburp ulnm, fusjf tbgoj qmh,l ftama
toxso orxaa ,tzpq mhoic drua- zooAg kgnrt blzqo maaoa dfmsm b,mhm
kurwu qxbtb odqbr nktpa luqeq .

Exercise 4

The text was enciphered using a polyalphabetic substitution cipher. Blank spaces were first deleted and then inserted at convenient locations.
bpivm mdznk azfkw lexpl urqjf wsejm deopd gqeg. qnwju clsjn lcwea
zfwpy vkdnw emzfk wlaew xohpy kpxzj xlhcm sjyer r,mxz cflco rgijr
jlaji xqbjj m,urf mixjc puqqj o,pdg tjmwq epufw lcaky ajbfi jrtyo
apcoe mvmmu gopuy olvjm kdfxj svfkw l.pdz nkazf jiewc scqcg pkmxz
cflco rgior fvxrt jvbjj m,llf krvxp grval ldmij yrsvf flcjj duhme
pemnj rmgio glyjr p,qcu zcvld voprx rliop ujabf rnmsu ox.cg mmjum
ilmpx vdpgj rikuf peuwf dgoes cqcuc gmqzv krewc rrxbs jabfr bpddm
pxvdp gvwcs dvbpx vfsru bwgqg ,rnpe bqbpc gmjyw fgwyb sztlk yqlc,
qcuzr ejsop gcgmq rvbtj vrjhc mdznk azfkw lqxur tksvw cs.

Submission Procedure. Create a file containing your solution. Call this file xxxxx0, where xxxxx is the Cornell network id of the team member whose net id is alphabetically smallest of your team. Then copy this directory to the following folder:

\\Goose\courses\cs513-spr00\proj01.submit

Don't be disturbed by warnings informing you that the file cannot be accessed after it has been copied.

Should you wish to revise your submission after you have copied it to our folder, then simply correct the files and recopy the entire directory---but this time use the name xxxxx1. Revisions to that should be named xxxxx2, and so on. We will grade only the largest-numbered file of a series.

What to Hand In. Not only should you submit plaintext but also submit documentation to justify your solution. This documentation should describe the strategy you employed, show the details for each of the steps of that strategy, show listings for any programs you wrote, show the output of these programs, and show how you transformed that output into your solution.

Needless to say, you may find it easiest if the "file" that you submit is, in fact, a directory. If you do submit a directory, then make sure it contains a README file that describes what other files the grader should read and in what order they should be read.