LIGN. 17 final

Consider the following partial credit card number: - 4777 2032 6784 207? - What value should the check digit be? Enter a single digit.

1

add the numbers 101101 and 11101 in binary then add 1111 to the result. whats the answer?

1011001

convert 25 into binary number:

11001

convert 107 into binary number:

1101011

the letter A in English has a frequency of about 8%. if we were to construct a MSC with homophones with 200 symbols in the cipher text alphabet, how many symbols should be used to represent A?

16 symbols

Consider the following part of an ISBN code: - 0-631-20126-? - What should the check digit be? Enter a single digit or an X

2

17871 (mod 6) =

3

[(7^123 x 8^4) (mod 6)]=

4

The following is a message that I encrypted as a rail fence cipher. How many rows did I use? TIVNEPEHSIEVRCIMSEEOTSYOLNJ

4 rows TIVNEPE|HSIEVRC|IMSEEOT|SYOLNJ

create a huffman tree with the following information: symbol- frequency c - 28 d- 43 e- 127 o- 75 r- 60 s- 63 v- 10

406

Consider the following Universal Product Code (UPC) number: - 0 67030 79549 4 - Let's say someone tells you that there is a single-digit error in this number, specifically on the third digit (7). What digit should this have been? Enter a single digit.

5

Suppose the following text is a message encoded with a vigenere cipher. Assuming that the keyword has more than two letters, how many letters does it have? ZPDXVPAZHSLZBHIWZBKMZNM a. 3 b. 4 c. 5 d. 6 or 3 e. 7

5 letters

for a 20 bit binary code to pass a spectral level 2 how many occurrences should there be? a.)there should be 10 occurrences of 1's and o's b.) there should be 5 occurrences on each of the four combinations c.) equal amount of 1's and 0 s 10 and 10

5 occurrences on each four combinations

the letter E in English has a frequency of about 12%. if we were to construct a MSC with homophones with 50 symbols in the cipher text alphabet, how many symbols should be used to represent E?

6 symbols

convert this binary number into decimal: 1011010

90

Let's say I want to encrypt the message GO LAKERS BOO BULLS using a 4 line rail fence cipher. what would the cipher text be?

GKBUOEOLLROLASBS

I've encoded a message using a 100 symbol MSC with homophones and after removing spaces from the plaintext, ended up with the following cipher text: 06 00 13 00 26 17 11 48 05 00 01 09 26 37 12 11 which of the following could be the message? a.) GO LAKERS BOO BULLS b.) GO PATRIOTS BOO YOU c.) GO COLTS BOO DALLAS

GO COLTS BOO DALLAS

I've encoded my first name DIANA in ASCII using the simple binary substitution cipher discussed in class using the 7 bit representation of a five-letter word as the key. the resulting cipher text is: 0001100 0001100 0001101 0000010 0001110

Hello

I completed a Vigenere encoding of my name (andykehler) with a keyword, which resulted in the ciphertext mrdrvshqqv. What was the keyword I used?

MEATLOAF

Let's say that I defined a substitution cipher that contains the following mappings. Plaintext symbol Cipher text symbol E 14, 16, 24, 44, 46 m 22, 27 z 02 s 11, 19,36 which of the following types of ciphers could my encryption system be an example of? a.) Caesar Shift b.)monoalphabetic substitution cipher with homophones. c.)Monoalphabetic substitution cipher with keyphrase. d.)nomenclator

MSC with homophones -Symbols in the plain alphabet can map to more than one symbol in the cipher alphabet. • Each symbol in the cipher alphabet maps to a single symbol in the plain alphabet.

with respect to the type of mapping between the plaintext alphabet and the ciphertext alphabet, which of the following types of cipher is a Caesar shift cipher conceptually most similar to? a.) caesar shift b.) MSC c.) MSC with homophones d.)Vigenere cipher e.) book cipher

Simple MSC both have a one to one mapping

with respect to the type of mapping between the plaintext alphabet and the ciphertext alphabet, which of the following types of cipher is a MSC with keyword conceptually most similar to? a.) caesar shift b.) MSC c.) MSC with homophones d.)Vigenere cipher e.) book cipher

Vigenere cipher both have a many to many mapping

suppose we applied a transposition cipher to the following sequence of bits, which is the 7 bit ASCII encoding of my first name (DIANA). which of the following is the only sequence that could possibly have been the result of this transposition? 10001001001001100000110011101000001 a.)01010101100101010100001010101000000 b.)10010101111001010011010100110101010 c.)11100101010011000001101010101011100

a.) 1's -13, 0's- 22= 35 bits

which is a simple recipe for doubling (multiply by 2) a number in binary? a.) add two zeros at the end of the number b.) remove two zeros from the end of the number c.)add one zero at the end of the number.

add one zero at the end of the number

a simple recipe for multiplying a binary number by 8 would be: a.) add three zeros b.)add two zeros c.) remove two zeros

add three zeros

a simple recipe for multiplying a binary number by 4 would be: a.) add three zeros b.)add two zeros c.) remove two zeros

add two zeros to the end of the number

Alice and bob want to exchange a secret message and so they use the diffie-hellman method to agree on a key. they choose Y=5 and P=71 so that the function they both use is 5^x (mod 7) further more, alice picks 3 as her secret number and bob picks 4 as his secret number. what's the number alpha that alice will send to bob? and vise versa? alpha and beta?

alpha:6 beta:2

which of the following ciphertexts could possibly be the result of encoding a message with a random one-time pad cipher? a.) RGFTHEBBGS b.) HHHHHHHH c.)QUELKAMUSD d.)SAYCHEESE e.) any of the above could d.) all except d

any of the above could as long as its truly random and only used once.

with respect to the type of mapping between the plaintext alphabet and the ciphertext alphabet, which of the following types of cipher is a MSC with homophones conceptually most similar to? a.) caesar shift b.) MSC c.) MSC with homophones d.)Vigenere cipher e.) book cipher

book cipher one -to -many

suppose I claimed that all of the following are the result of applying some type of transposition cipher to the message GO LAKERS BOO BULLS and then removing spaces. without a lot of effort you react by telling me that one of these could NOT possibly be a transposition cipher text for this message. which one? a.) SLBOSEAOLUOBRKLG b.) GLKRBOULOAESOBLS c.) GOLANERSBOSLLUBS d.) GKBUOEOLLROLASBS

c.) GOLANERSBOSLLUBS transposition is about changing the places of the existing characters, not substituting characters. in the plaintext there is no N.

Let's say I created a ciphertext with a simple MSC, I want to make it more secure so I perform another MSC right after the first one. which of the following statements are true? a.) it will be more secure since in order to break the cipher you have to do two decriptions in order to break it. b.) less secure because due to the second encryption will become more vulnerable to frequency analysis than if I had used just one MSC. c.) it will be equally secure than if I had just used one MSC since for any two monoalphabetic substitution ciphers applied one after the other, there exists another, single monoalphabetic substitution cipher that achieves the same result.

c.) it will be equally secure as if you were to have used one.

using the tree in the previous question, which of the following words would receive a longer encoding than if we were to have used a minimal-fixed length code for the same alphabet? 1. dad 2.cad 3. cab 4.dab 5. none

cad for 7 bits

consider the following variable length code for symbols d-i, which binary code should be changed? symbol binary code a 10 b 01 c 110 d 0110 e 0010 f 0001 a. None (It is already a prefix-free code). b. Change the code for a to 1. c. Change the code for b to 00. d. Change the code for c to 100. e. Change the code for d to 0000.

d for 0000

create a huffman tree with the following symbol and frequency numbers symbol frequency a 82 b 15 c 28 d 42 type in bit string for the word DAD

dad= 01101

Let's say I typed out the following Visa card number: - 4888 6053 7432 0139 Is this number valid, and if not, which of the following mistakes could have been made? a. This is a valid Visa card number. b. The 5th digit (6) should have been a 5. c. The 6th digit (0) should have been a 1. d. The 7th digit (5) should have been a 4. e. The 8th digit (3) should have been a 2.

e- 3 should have been a 2

Suppose we have a Caesar shift cipher that shifts the English alphabet by an odd number of times, applying the cipher repeatedly -- each time to the output of the last time -- will never recover the plaintext again. true or false?

false 13 is an odd number which also happens to be half of the total letters in the alphabet. If we were to apply 13 times each time to the output of the last time, it will recover the plaintext again.

What is the Vigenere encoding of my name (andykehler) with the keyword goofball?

gbrdleswkf

In order for a 20 bit binary code to pass the spectral level 1 test what pattern of number should it show on the four different possible combinations? a.) 5 all across the board? b.) 10 at least in two combinations? c.) have an equal amount of 1's and 0's

have an equal amount of symbols for example in a code with 20 binary numbers there should be 10 ones and 10 zeros

with alpha 6 (mod 7) and beta 2(mod 7) whats they key will bob and alice agree at the end of process?

key=1

consider the following variable-length code for the symbols n-u. should any of the binary code be changed to make it a prefix-free code? symbol binary code n 0110 o 11 p 100 q 010 r 000 s 01001 t 01111 u 01110 a.) n to 0111 b.) q to 001 c.) s to 01101 d.) u to 011110

q-001

what would be a simple recipe for dividing a number by two in binary? a.) add two zeros at the end of the number b.) remove one zero from the end of the number c.)add one zero at the end of the number.

remove one zero from the end of the number.

Suppose we have a Caesar shift cipher that shifts the English alphabet by 13 times each time to the output of the last time -- will always recover the plaintext again. True or false?

true there are 26 letters in the alphabet. if we shift it 13 which is just shifting half of the alphabet. It will eventually lead us to the plaintext.

Suppose we have a Caesar shift cipher that shifts the English alphabet N times - No matter what N is, applying the cipher 26 times -- each time to the output of the last time -- will always recover the plaintext again. true or false?

true yes because there are 26 letters in the alphabet no matter the number you choose to shift if performed 26 times it will lead us to the original plaintext.

Let's say I encrypt a message using a monoalphabetic substitution cipher with keyphrase, using the keyphrase GO LAKERS BOO BULLS the letter N in the alphabet will be encoded with what letter of the cipher text?

w