Name:
1/
2/
3/
4/
5/
6/
7/
8/
Total/
Please do not write in the spaces above.
Directions: This exam must be handed in at the beginning of the in-class exam on Friday. You may
not use anything but your class notes, class book, and the maplets. You may not discuss the
problems with anyone (other than me).
Make sure to break the plaintext into individual words. Show work on the cryptanalysis problems.
Please attach this signed cover sheet to your work.
Good luck!
Please sign:
I,
content, with anyone.
, affirm that I have not discussed this exam, its questions, or its
Note: These are all to be done on maplets – do not attempt to do these by hand, unless I explicitly tell
you to do so. Also, make sure you break these up into words in English.
1. Break the following cipher, which was made using a random substitution cipher:
URTLT EAPP HT PAUUPT LWHK MJQ QAKMCCYAJUSTJUK TVTLXERTLT MJQ ET MLT
MPP MCU UY TOCTBU UYY SWBR HWU URTJ AG YJT KBRTST YG RMCCAJTKK
GMAPK RWSMJ JMUWLT UWLJK UY MJYURTL AG URT GALKU BMPBWPMUAYJ AK
ELYJZ ET SMFT M KTBYJQ HTUUTL ET GAJQ BYSGYLU KYSTERTLT
Hint: The most common letter of the ciphertext is the most common English letter.
Give a detailed description of your process here, including any steps that didn’t work.
2. Break the following cipher, which was made using a keyword columnar cipher, and with crib
“and courage as”:
ESEHR DSTUT ETISE SAENC AYULK FSATA AESHM WNTNR GOSGS EAEIG SHRHT
NFWIE TRNGD OHIHR SHEDE AN
Give a detailed description of your process here, including any steps that didn’t work.
3. Break the following phase shift cipher: ALAKL GLZWU JWVAL GXZME SFFSL MJWLZ
SLWPU WHLOZ WJWAL KKWDX AKZFW KKAKT JGMYZ LAFLG HDSQA LDGNW KEGJW
JWSVA DQLZS FALZS LWK
Give a detailed description of your process here, including any steps that didn’t work.
4. Break the following affine cipher, where it is somehow known that the plaintext letter y
corresponds to the ciphertext letter D and the plaintext letter o corresponds to the ciphertext
letter J: DJVIH KPWCH XURXU DJVCI PHADJ VIHKP EPPGX UDJVC RIJPR DJVLH
URGPP CDJVC RPQEH UDAXC PLGXJ UDJVL IJJRP DJVCP JUDJV CJZUH UADJV
BUJZZ IHGDJ VBUJZ HUADJ VHCPG IPJUP ZIJQQ APLXA PZIPC PGJTJ
Give a detailed description of your process here, including any steps that didn’t work.
5. Break the following hill cipher, which came from a 4x4 matrix, with a crib at the end of the
message containing the words “cause for pride and contentment”.
WGOPA FBHPP JHZOL MSBFP ZISDX PNVNO ESIKM IKEIV XCILO QZYHY NTWZV
YBMRH PJWVV MVMIG KTNFN DLMIS ZEGUO MEUBA TTUPY VKCWX EECYA CSXHO
CHXYS BARXX TFYYE GDGUY KSLEX ZYLBC ILTKE PBZWM FKAMG KRQOB IHPPW
HVBUY DOCDW DXPRK DWXGW OOMVO HAKHB UUJTR UHPPS JQJIS FUSOE WROTX
BHGKK QCPOJ PSLZZ CXDPR MEMON XAMZV TXVLE GCLRE SQPCK QYCBD PVOQF
OCDWD VJJWG OEJIY VYGSP WQXTS EMBYJ NUYTQ LVVOF JAMEC PYSNF PWJUV
YZGRU TDNSC WNLV
6. a. Find the gcd(232455556,63846837). Then find s and t.
exists, find it.
-1
b. Find 75476548 mod111100001111
c. Find 54653467332534622 mod 1773667364836483746
-1
If 63846837 mod232455556
7. Alice wants to communicate with Bob using RSA. Bob chooses primes p=435374537459 and
q=2352673529. He also chooses e=994123.
a. Find m,f,d.
b. List out Bob’s public and private keys (along with their values)
c. Encrypt the plaintext “not all those who wander are lost”
d. Decrypt the ciphertext
[622823715889542502968,
613954354866029247777,
910340334116712592683,
453362927578325616029,
867981567811892203920,
414603520096219515970,
468332412731590148803]
8. I want you to do the following by hand, showing all work:
This is another RSA example. With smaller numbers, but still not the “light” version from the
last exam.
Alice wants to communicate with Bob using RSA. Bob chooses primes p=331, q=163.
Additionally, he chooses e=233.
a.
b.
c.
d.
e.
Find m, f by hand, showing all work.
Use the Euclidean algorithm to find the gcd of e and f, showing all work.
Use the Euclidean algorithm to find d, showing all work.
Write the message “him!” in ASCII, breaking it into blocks that are all less than m.
Encrypt your work from part d, using modular exponentiation, showing all work. . (OK. So if
you encrypt “hi” you will get full credit. If you encrypt “him!” you will get extra credit.)