Chapter 1 – An Introduction to Cryptography

1.1 – Simple substitution ciphers

Exercise 1.1 For this exercise, the authors made a cipher wheel available which can be printed and cut out. One way to do this is to print two copies and cut out the inner wheel from one and the outer wheel from the other. For the purposes of the exercise, a clockwise rotation means that the outer wheel is rotated clockwise with respect to the inner wheel. Thus, if you are rotating the inner wheel, you must turn it counter-clockwise to achieve the same result.

(a) The ciphertext corresponding to a rotation of 11 clockwise is

LALRP ZQSTD EZCJT DHZCE SLGZW FXPZQ WZRTN

(b) The plaintext is a quote from George Bernard Shaw’s “Mrs. Warren’s Profession”. Please note that there is an error in the ciphertext as printed in the first edition of the book. See the errata page.

AOLYL HYLUV ZLJYL AZILA ALYAO HUAOL ZLJYL AZAOH ALCLY FIVKF NBLZZ LZ
there areno secre tsbet terth anthe secre tstha tever ybody guess es

(c) The plaintext is

XJHRF TNZHM ZGAHI UETXZ JNBWN UTRHE POMDN BJMAU GORFA OIZOC C
whena ngryc ountt enbef oreyo uspea kifve ryang ryanh undre d

Exercise 1.2

(a) The ciphertext was encrypted with a rotation of 3 clockwise. The plaintext is

LWKLQ NWKDW LVKDO OQHYH UVHHD ELOOE RDUGO RYHOB DVDWU HH
ithin kthat ishal lneve rseea billb oardl ovely asatr ee

(b) The ciphertext was encrypted with a rotation of 9 clockwise. The plaintext is

UXENR BWXCU XENFQ RLQJU CNABF QNWRC JUCNA JCRXW ORWMB
lovei snotl ovewh ichal tersw henit alter ation finds

(c) The ciphertext was encrypted with a rotation of 19 clockwise. The plaintext is

BGUTB MBGZT FHNLX MKTIP BMAVA XXLXT EPTRL EXTOX KHHFY HKMAX FHNLX
inbai tinga mouse trapw ithch eesea lways leave roomf orthe mouse

Exercise 1.3

(a) The ciphertext is

IBXFE PAQLB QAAXW QWIBX FSVAX W

(b) The decryption table is

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

(c) The plaintext is

IBXLX JVXIZ SLLDE VAQLL DEVAU QLB
these cretp asswo rdiss wordf ish

Exercise 1.4

(a) The plaintext is

JNRZR BNIGI BJRGZ IZLQR OTDNJ GRIHT USDKR ZZWLG OIBTM NRGJN
these chara cters asone might readi lygue ssfor macip herth

IJTZJ LZISJ NRSBL QVRSI ORIQT QDEKJ JNRQW GLOFN IJTZX QLFQL
atist osayt heyco nveya meani ngbut thenf romwh atisk nowno

WBIMJ ITQXT HHTBL KUHQL JZKMM LZRNT OBIMI EURLW BLQZJ GKBJT
fcapt ainki ddico uldno tsupp osehi mcapa bleof const ructi

QDIQS LWJNR OLGRI EZJGK ZRBGS MJLDG IMNZT OIHRK MOSOT QHIJL
ngany ofthe morea bstru secry ptogr aphsi madeu pmymi ndato

QBRJN IJJNT ZFIZL WIZTO MURZM RBTRZ ZKBNN LFRVR GIZFL KUHIM
nceth atthi swaso fasim plesp ecies suchh oweve raswo uldap

MRIGJ LJNRB GKHRT QJRUU RBJLW JNRZI TULGI EZLUK JRUST QZLUK
peart othec rudei ntell ectof thesa ilora bsolu telyi nsolu

EURFT JNLKJ JNRXR S
blewi thout theke y

(b) The plaintext is

KZRNK GJKIP ZBOOB XLCRG BXFAU GJBNG RIXRU XAFGJ BXRME MNKNG
iwasi think welle ducat edfor thest andar dofth edaym ysist

BURIX KJRXR SBUER ISATB UIBNN RTBUM NBIGK EBIGR OCUBR GLUBN
erand ihada germa ngove rness avery senti menta lcrea tures

JBGRL SJGLN GJBOR ISLRS BAFFO AZBUN RFAUS AGGBI NGLXM IAZRX
hetau ghtus thela nguag eoffl owers aforg otten study nowad

RMNVL GEANG CJRUE KISRM BOOAZ GLOKW FAUKI NGRIC BEBRI NJAWB
aysbu tmost charm ingay ellow tulip forin stanc emean shope

OBNNO ATBZJ KOBRC JKIRR NGBUE BRINK XKBAF QBROA LNMRG MALUF
lessl ovewh ileac hinaa sterm eansi dieof jealo usyat yourf

BBG
eet

(c) The plaintext is

GSZES GNUBE SZGUG SNKGX CSUUE QNZOQ EOVJN VXKNG XGAHS AWSZZ
iamfa irlyf amili arwit hallf ormso fsecr etwri tinga ndamm

BOVUE SIXCQ NQESX NGEUG AHZQA QHNSP CIPQA OIDLV JXGAK CGJCG
yself autho rofat rifli ngmon ograp hupon subje ctinw hichi

SASUB FVQAV CIAWN VWOVP SNSXV JGPCV NODIX GJQAE VOOXC SXXCG
analy zeone hundr edsep arate ciphe rsbut iconf essth atthi

OGOVA XGNVU BAVKX QZVQD LVJXQ EXCQO VKCQG AMVAX VWXCG OOBOX
sisen tirel ynewt omeob jecto fthos ewhoi nvent edthi ssyst

VZCSO SPPSN VAXUB DVVAX QJQAJ VSUXC SXXCV OVJCS NSJXV NOJQA
emhas appar ently beent oconc ealth atthe secha racte rscon

MVBSZ VOOSH VSAWX QHGMV GWVSX CSXXC VBSNV ZVNVN SAWQZ ORVXJ
veyam essag eandt ogive ideat hatth eyare merer andom sketc

CVOQE JCGUW NVA
hesof child ren

1.2 – Divisibility and greatest common divisors

1.3 – Modular arithmetic

1.4 – Prime numbers, unique factorization, and finite fields

1.5 – Powers and primitive roots in finite fields

1.6 – Cryptography before the computer age

1.7 – Symmetric and asymmetric ciphers

  1. March 27, 2011 at 5:38 PM | #1

    I like your writing style, and I’m hoping for more posts like this one.

  1. No trackbacks yet.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

Follow

Get every new post delivered to your Inbox.

%d bloggers like this: