Cryptography Final Actual Exam Questions and CORRECT Answers

Cryptography Final Actual Exam
Questions and CORRECT Answers
Keys used in an encryption, and the corresponding decryption functions must be the same -
CORRECT ANSWER✔✔- False


For a Shannon cipher(E,D) defined over (k,m,c), D(k, E(k,m))=m - CORRECT
ANSWER✔✔- True


Knowing that entropy is a measure of randomness (more randomness =less predictability =
more entropy), we can tell that ABCDEFGHHHHHHH has higher entropy than ABCDEFGH
- CORRECT ANSWER✔✔- False


For enhanced security, an organization should use secret encryption algorithms that nobody
knows - CORRECT ANSWER✔✔- False



Hash of a plaintext is usually shorter than its ciphertext - CORRECT ANSWER✔✔- True


In English language, the frequency of A is less than the "frequency of AB+ frequency of AC"
- CORRECT ANSWER✔✔- False


If a Shannon cipher (E, D) defined over (k,m,c) is perfectly secure, then the length of k>=the
length of m - CORRECT ANSWER✔✔- True


Knowing that entropy is a measure of randomness (more randomness = less predictability =
more entropy), we can tell that ABCDEFGHIJKLMN has higher entropy than ABCDEFGH -
CORRECT ANSWER✔✔- True


In a game, Stefany randomly picks a letter from "A", "B" and "C" and Brandon randomly
picks a number from "1","2","3" and "4". To win, Stefany needs to guess Brandon's number
and Brandon needs to guess Stefany's letter. If played many times who is expected to win the
game? - CORRECT ANSWER✔✔- Brandon

, If we can guess the bits (0's and 1's) of a digital key by the power consumption of a decryptor
circuit, we can call our effort a - CORRECT ANSWER✔✔- side channel attack


During Diffie-Hellman key exchange, the order of key exchange (i.e., which party sends the
part of the "key" to the other party first) does not matter - CORRECT ANSWER✔✔- True



E(alpha) is easily computable - CORRECT ANSWER✔✔- True



(2^3)^2 = - CORRECT ANSWER✔✔- (2^2)^3



In RSA endcryption, E(D(M))= D(E(M)) - CORRECT ANSWER✔✔- True



(2^3)^2 mod 3 = - CORRECT ANSWER✔✔- 1


Prime p and generator g in Diffie-Hellman key exchange algorithm, ideally, should be kept
secret - CORRECT ANSWER✔✔- False


Use of the same cryptographic key for multiple purposes is a recommended key management
practice - CORRECT ANSWER✔✔- False


Functions E() and F() in Diffie-Hellman key exchange algorithm must be kept secret -
CORRECT ANSWER✔✔- False


Protocol ElGamal key agreement (Menezes, Page 517) is nothing but the Diffie-Hellman key
exchange with part of the "key" computed by one party is made public - CORRECT
ANSWER✔✔- True


Given E() and the value of E(alpha), "alpha" is easily computable - CORRECT
ANSWER✔✔- False



If a, b, c are binary variables, a XOR b XOR c= a + b + c mod 2 - CORRECT ANSWER✔✔-
True