Deck 8: Cryptanalysis: Advanced Dictionaries and Lists, Regular Expressions

Question 1

One of the most secure algorithms for encryption today is called:

A) brute force.
B) RSA.
C) the Turing cipher.
D) the rail fence cipher.

Answer 1

B

Question 2

Manually trying every possible combination of letters to decode a message is called:

A) breaking.
B) cryptomania.
C) brute force.
D) encryption.

Answer 2

C

Question 3

The rail-fence cipher with a rail size of ___ breaks the plaintext into strings consisting of characters with odd and even numbered indexes.

A) 1
B) 2
C) 3
D) 4

Answer 3

B

Question 4

Case Study 1:
1. def railBreak(cipherText):
2. wordDict = createWordDict('wordlist.txt')
3. cipherLen = len(cipherText)
4. maxGoodSoFar = 0
5. bestGuess = "No words found in dictionary"
6. for i in range(2, cipherLen + 1):
7. words = railDecrypt(cipherText, i)
8. goodCount = 0
9. for w in words:
10. if w in wordDict:
11. goodCount = goodCount + 1
12. if goodCount > maxGoodSoFar:
13. maxGoodSoFar = goodCount
14. bestGuess = " ".join(words)
15. return bestGuess
-Refer to the session in the accompanying Case Study 1. What pattern is used on lines 12-14?

A) Minmax
B) Rail break
C) Cryptology
D) Brute force

Question 5

Case Study 1:
1. def railBreak(cipherText):
2. wordDict = createWordDict('wordlist.txt')
3. cipherLen = len(cipherText)
4. maxGoodSoFar = 0
5. bestGuess = "No words found in dictionary"
6. for i in range(2, cipherLen + 1):
7. words = railDecrypt(cipherText, i)
8. goodCount = 0
9. for w in words:
10. if w in wordDict:
11. goodCount = goodCount + 1
12. if goodCount > maxGoodSoFar:
13. maxGoodSoFar = goodCount
14. bestGuess = " ".join(words)
15. return bestGuess
-Refer to the session in the accompanying case study. What is the function of
" ")join(words) on line 14?

A) It glues together all of the strings in the list words separating them using the space character.
B) It creates a dictionary of all the words in the list words.
C) It separates each word in the list words into a range.
D) It sets all of the values in words to a single space.

Question 6

____ order takes the first row of the table and stores all the values on that row one after the other, followed by the second row and the third, and so on.

A) Column major
B) Row major
C) Encrypted
D) Rail post

Question 7

What of the following is one of the most frequently occurring letters in the English language?

A) B
B) E
C) U
D) S

Question 8

What method sorts a list of values from largest to smallest?

A) reverse
B) reversesort
C) sort(reverse = True)
D) sort('descending')

Question 9

What is the value of myList after the following statement?
MyList = myList.sort().

A) None
B) The original list, sorted in ascending order
C) The original list, sorted in descending order
D) An empty list

Question 10

Case Study 2:
1. def maybeAdd(ch, toList):
2. if ch in 'abcdefghijklmnopqrstuvwxyz'
and ch not in toList:
3. toList.append (ch)
-Refer to the session in the accompanying Case Study 2. What is the value of myList after the following code is executed?
>>> myList = []
>>> maybeAdd('a', myList)

A) []
B) ['a']
C) ['abcdefghijklmnopqrstuvwxyz']
D) None

Question 11

Case Study 2:
1. def maybeAdd(ch, toList):
2. if ch in 'abcdefghijklmnopqrstuvwxyz'
and ch not in toList:
3. toList.append (ch)
-Refer to the session in the accompanying Case Study 2. What is the value of myList after the following code is executed?
>>> myList
['a', 'b']
>>> maybeAdd('a', myList)

A) ['a', 'a', 'b']
B) ['a', 'b']
C) ['abcdefghijklmnopqrstuvwxyz']
D) None

Question 12

What three-letter word appears most often in War of the Worlds?

A) The
B) And
C) Was
D) Had

Question 13

In Python, regular expressions are available through the ____ module.

A) pattern
B) wildcard
C) regex
D) re

Question 14

In a regular expression, a part of the expression surrounded by () is called a(n):

A) capture group.
B) cluster.
C) object.
D) wildcard.

Question 15

Some of the first computer scientists were deeply involved in cryptanalysis.

Question 16

When decrypting using the rail fence cipher, one can easily see how many rails were used and encrypt the message by simply examining the encoded message.

Question 17

If we want to store a two-dimensional table in a computer's memory, we need to map from the row, column coordinates, which correspond to a cell in the table, to a location in memory.

Question 18

One effective way to ignore non-letter characters is to add them to the string before we start counting.

Question 19

Using the setDefault pattern is efficient for adding values to a dictionary.

Question 20

Match each definition with its term.
-Allows us to match strings using patterns.

A) Regular expression
B) Cryptanalysis
C) Capture group
D) Brute force

Question 21

Match each definition with its term.
-Refers to the field of code breaking.

A) Regular expression
B) Cryptanalysis
C) Capture group
D) Brute force

Question 22

Match each definition with its term.
-Allow us to determine what characters in a target word match letters in different
Parts of a given pattern.

A) Regular expression
B) Cryptanalysis
C) Capture group
D) Brute force

Question 23

Match each definition with its term.
-Refers to trying all possible solutions.

A) Regular expression
B) Cryptanalysis
C) Capture group
D) Brute force

Question 24

Describe the use of brute force to decrypt encrypted messages.

Question 25

How can a dictionary be used to improve upon a brute force approach to decrypting a rail fence cipher?

Question 26

What are the benefits of using a dictionary over a list when looking up values?

Question 27

Describe the use of the join method.

Question 28

What is the difference between row major order and column major order?

Question 29

Briefly describe how to crack a substitution cipher.

Question 30

Describe the two keyword parameters to the sort method.

Question 31

Explain how to identify the difference between vowels and consonants in the English language.

Question 32

Describe the function of regular expressions and explain how to use them in Python.