Code Busters Practice Test, Slides of Cryptography and System Security

Download Code Busters Practice Test and more Slides Cryptography and System Security in PDF only on Docsity! Code Busters Practice Test You have 45 Minutes to complete this test Record your time when you finish the first question For added realistic test conditions, have someone else know the answer to the first question and tell you if you are correct or incorrect. If incorrect, you may try again. Record the time when you get the question correct. For the purposes of this test, A=0,B=1,C=2… Z=25 For mono-alphabetic substitution cyphers the only constraint on ciphertext alphabets is that no letter may decrypt to itself You may need the following table 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 A 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 B 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 A C C D E F G H I J K L M N O P Q R S T U V W X Y Z A B D D E F G H I J K L M N O P Q R S T U V W X Y Z A B C E E F G H I J K L M N O P Q R S T U V W X Y Z A B C D F F G H I J K L M N O P Q R S T U V W X Y Z A B C D E G G H I J K L M N O P Q R S T U V W X Y Z A B C D E F H H I J K L M N O P Q R S T U V W X Y Z A B C D E F G I I J K L M N O P Q R S T U V W X Y Z A B C D E F G H J J K L M N O P Q R S T U V W X Y Z A B C D E F G H I K K L M N O P Q R S T U V W X Y Z A B C D E F G H I J L L M N O P Q R S T U V W X Y Z A B C D E F G H I J K M M N O P Q R S T U V W X Y Z A B C D E F G H I J K L N N O P Q R S T U V W X Y Z A B C D E F G H I J K L M O O P Q R S T U V W X Y Z A B C D E F G H I J K L M N P P Q R S T U V W X Y Z A B C D E F G H I J K L M N O Q Q R S T U V W X Y Z A B C D E F G H I J K L M N O P R R S T U V W X Y Z A B C D E F G H I J K L M N O P Q S S T U V W X Y Z A B C D E F G H I J K L M N O P Q R T T U V W X Y Z A B C D E F G H I J K L M N O P Q R S U U V W X Y Z A B C D E F G H I J K L M N O P Q R S T V V W X Y Z A B C D E F G H I J K L M N O P Q R S T U W W X Y Z A B C D E F G H I J K L M N O P Q R S T U V X X Y Z A B C D E F G H I J K L M N O P Q R S T U V W Y Y Z A B C D E F G H I J K L M N O P Q R S T U V W X Z Z 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 Question 2 Worth 200 pts The following ciphertext is a mono-alphabetic substitution from Jean Jacques Rousseau’s Social Contract. One thing to note is that Rousseau likes to use masculine pronouns XLY TD MZCY QCPP, LYO PJPCJHSPCP SP UD TY NSLTYD. SPCP’D ZYP HSZ ESTYVD SP UD DSP XLDEPC ZQ ZESPCH, JPE SP UD XZCP PYDWLGPO ESLY ESPJ LCP. 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 freq 0 0 9 10 6 0 1 3 0 4 0 7 1 1 2 21 2 0 12 4 3 1 1 3 9 6 L M N O P Q R S T U V W X Y Z A B C D E F G H I J K Man is born free, and everywhere he is in chains. Here’s one who thinks he is the master of others, yet he is more enslaved than they are. Question 3 Worth 400 pts The following cipher text encoded using a mono-alphabetic substitution is from the last 2 sentences in the book Don Quixote. It is written in the past tense. The plain text is in the original language: Spanish. Accents are ignored. This cipher uses a 27-letter alphabet, Ñ is considered its own letter while CH, LL are considered 2 each. HNGAÑIYRN, YRPOÑ, AN JY ÑZZYUPÑI TVN FN LN AYAÑ AN HYGNZNG JÑZÑ ZÑRÑ XÑ LYZPNIAÑFN ZYNG NI NJ NGGÑG NI TVN XÑ ZYPAÑ AN TVN LVBÑ X LYX ZYBYJJNGO YIAYIFNU NI NJ RVIAÑ. A B C D E F G H I J K L M N Ñ O P Q R S T U V W X Y Z freq 10 2 0 0 0 3 8 2 9 6 0 4 0 23 16 2 4 0 4 0 3 2 5 0 4 14 9 Y B Z A N M O L P K Q J R I S Ñ H T G U F V E D W X C Perdoname, amigo, de la occasion que te he dado de parecer loco como yo haciendote caer en el error en que yo he caido de que hubo y hay caballeros andantes en el mundo. Question 4 Worth 500 pts No hint for this one CX CO I NSFCEJ EB ACPCD YIF. FSRSD ONIASOTCNO, OXFCUCMB BFEV I TCJJSM RIOS, TIPS YEM XTSCF BCFOX PCAXEFQ IKICMOX XTS SPCD KIDIAXCA SVNCFS 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 freq 5 4 16 4 5 9 0 0 10 3 2 0 2 4 8 4 1 2 12 5 1 4 0 8 2 0 I R A J S B K T C L U D V M E N W F O X G P Y H Q Z It is a period of civil war. Rebel spaceships, striking from a hidden base, have won their first victory against the evil Galactic Empire. Question 7 Worth 700 pts No clue, no punctuation, no spaces. CJRN OPKD YJAH ZWPO DQZI ZQZM NZZI VNJI JAVY VHJM VYVP BCOZ MJAZ QZWZ AJMZ 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 freq 4 1 2 2 0 0 0 2 3 7 1 0 4 3 3 3 3 1 0 0 0 5 2 0 3 11 V W X Y Z A B C D E F G H I J K L M N O P Q R S T U How stupid of me! But I’ve never seen a Son of Adam or a Daughter of Eve before. Question 8 Worth 300 pts Encode the following sentence using an affine cipher with a key of 5x+4 SPACE, THE FINAL FRONTEIR. THESE ARE THE VOYAGES OF THE STARSHIP ENTERPRISE. 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 Value 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 5x 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 5x + 4 4 9 14 19 24 29 34 39 44 49 54 59 64 69 74 79 84 89 04 99 104 109 114 119 124 129 Ans mod 26 4 9 14 19 24 3 8 13 18 23 2 7 12 17 22 1 6 11 16 21 0 5 10 15 20 25 E J O T Y D I N S X C H M R W B G L Q V A F K P U Z QBEOY, VNY DSREH DLWRVYSL. VNYQY ELY VNY FWYEIYQ WD VNY QVELQNSB YRVYLBLSQY. Question 9 Worth 600 pts This affine ciphertext is encoded from a cryptography textbook. It is the first 2 sentences from the first chapter on modular arithmetic. The word modular occurs once and the prefix crypto occurs twice. The key is ax + b. Decrypt the message or determine the key XBFO LA UOVN YLLJ PVQQ YT NSTEU QLLJVRH RU UOT RSSQVFRUVLEN LA XLMBQRG RGVUOXTHVF, NVEFT VU VN ABEMRXTEBRQ UL XLMTGR FGDSULHGRSOD REM SBUQVF JTD FGDSULNDNUTXN VE SRGUVFBQRG. OTEFT, VE UOVN FORSUTG PT VEUGLMBFT UOT YRNVF FLEFTSUN REM UTFOEVZBTN PT NORQQ GTZBVGT 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 Value 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 freq 3 9 0 5 13 15 12 3 0 3 0 14 6 13 11 3 10 17 10 21 19 19 0 6 3 2 Much of this book will be spent looking at the applications of modular arithmetic, since it is fundamental to modern cryptography and public key cryptosystems in particular. Hence, in this chapter we introduce the basic concepts and techniques we shall require. 7x+17 𝑎𝑑𝑗 ! 7 14 11 24 6 17 0 8 11 * = ⎝ ⎜ ⎛ + 36 17 8 113 − 314 11 8 113 + 314 11 6 173 − 324 17 0 113 + 37 11 0 113 − 3 7 11 24 173 + 314 11 6 173 − 3 7 11 24 173 + 3 7 14 24 6 3⎠ ⎟ ⎞ = ! −70 −66 172 −264 77 145 −72 −145 294 * = ! 17 21 27 3 19 0 15 0 4 * 𝑚𝑜𝑑 29 17 ∗ ! 17 21 27 3 19 0 15 0 4 * = ! 28 9 24 25 20 0 23 0 10 * Question 12 300 pts Encode the following plain text using a Vigenère Cipher with a key of BUTTERCUP LIFE IS PAIN, HIGHNESS. MCZY MJ RUYO, BNGLHGOH. Question 13 300 pts Decrypt this Baconian cipher with a 24 letter alphabet (I,J and U,V are one letter) ABABBABAAABABABAABAA ABABBABBBAABBABAABBA AAAAAABBABAAABB ABBBBBAAABABBBABAABAABBBBAABAABAAAB Live long and prosper Question 15b 200 points Using the keys above, encrypt the number 81 81^5 mod 6557 = 1296 Question 15c 100 pts Mathematically set up how to decrypt the ciphertext 2345 using the above key 2345^ 5117 mod 6557 Question 16 450 pts Crack this Vigenère cipher given the following plain text: THE BOY WHO LIVED And the following ciphertext: IHXSCLQZDLBMSQ PATRONUS