WGU INTRO TO CRYPTOGRAPHY
OBJECTIVE ASSESSMENT PREP (D830-
D334) PREMIUM QUESTIONS &
EXPLANATIONS
Pass your WGU cryptography exam on the first attempt with this
comprehensive bank of realistic practice questions and verified
answers. Every question features a deep-dive rationale formatted
with clear bolding and italics to break down complex symmetric,
asymmetric, and post-quantum concepts effortlessly. Master
historical ciphers, PKI, block modes, and hashing structures using
this highly scannable, premium study tool optimized for rapid
memory retention.
Section 1: Classical Cryptography & Historical
Ciphers
Q1. Which type of cipher rearranges the letters
of a plaintext message without changing the
actual letters themselves?
A) Monoalphabetic cipher
B) Polyalphabetic cipher
C) Transposition cipher
D) Substitution cipher
Correct Answer: C
Rationale: Transposition ciphers shift the
positions of characters within a message
according to a specific system or key, leaving
the letters themselves intact but changing their
,order. Substitution ciphers, on the other hand,
replace characters with different characters.
Q2. The Vigenère cipher is less vulnerable to
simple frequency analysis than the Caesar
cipher because it is a:
A) Symmetric block cipher
B) Polyalphabetic substitution cipher
C) Transposition cipher
D) Asymmetric key stream cipher
Correct Answer: B
Rationale: The Vigenère cipher uses a repeating
keyword to change the shift value across
successive letters. Because a single plaintext
letter can map to multiple ciphertext letters
depending on its position, it is a polyalphabetic
substitution cipher that flattens standard single-
letter frequency spikes.
Q3. Under what conditions is a One-Time Pad
(OTP) mathematically unbreakable (information-
theoretic security)?
A) The key is at least 128 bits long and generated by
an approved software PRNG.
B) The key is truly random, as long as or longer than
the plaintext, used only once, and kept completely
,secret.
C) The key is shared securely using an RSA 2048-
bit key exchange.
D) The ciphertext undergoes at least 16 rounds of
substitution and permutation.
Correct Answer: B
Rationale: Claude Shannon proved that a One-
Time Pad achieves perfect secrecy only when
the key is completely random, equal to or greater
than the message length, never reused in whole
or in part, and completely protected from
disclosure.
Q4. An attacker is attempting to break a
historical cipher. They possess both the
plaintext and the corresponding ciphertext for
several historical messages. What type of
cryptographic attack is this?
A) Ciphertext-only attack
B) Known-plaintext attack
C) Chosen-plaintext attack
D) Chosen-ciphertext attack
Correct Answer: B
Rationale: In a known-plaintext attack (KPA), the
cryptanalyst has access to the ciphertext and its
corresponding plaintext. They use this
, information to deduce the secret key or the
algorithm's underlying logic.
Q5. What fundamental cryptographic design
feature allowed Alan Turing and the team at
Bletchley Park to exploit and break the German
Enigma rotor machine?
A) The machine could never encrypt a letter as itself.
B) The machine relied on a completely public key
distribution system.
C) The rotors only spun backward during decryption.
D) The plugboard was limited to exactly three
physical wires.
Correct Answer: A
Rationale: A key design flaw of the Enigma
machine was its reflector mechanism, which
prevented any letter from ever mapping to itself
in the ciphertext. This predictability allowed
codebreakers to eliminate thousands of invalid
key configurations instantly using "cribs."
Q6. If an alphabet substitution cipher shifts
every letter by 3 positions (e.g., A becomes D),
what is the specific name of this historical
cipher?
OBJECTIVE ASSESSMENT PREP (D830-
D334) PREMIUM QUESTIONS &
EXPLANATIONS
Pass your WGU cryptography exam on the first attempt with this
comprehensive bank of realistic practice questions and verified
answers. Every question features a deep-dive rationale formatted
with clear bolding and italics to break down complex symmetric,
asymmetric, and post-quantum concepts effortlessly. Master
historical ciphers, PKI, block modes, and hashing structures using
this highly scannable, premium study tool optimized for rapid
memory retention.
Section 1: Classical Cryptography & Historical
Ciphers
Q1. Which type of cipher rearranges the letters
of a plaintext message without changing the
actual letters themselves?
A) Monoalphabetic cipher
B) Polyalphabetic cipher
C) Transposition cipher
D) Substitution cipher
Correct Answer: C
Rationale: Transposition ciphers shift the
positions of characters within a message
according to a specific system or key, leaving
the letters themselves intact but changing their
,order. Substitution ciphers, on the other hand,
replace characters with different characters.
Q2. The Vigenère cipher is less vulnerable to
simple frequency analysis than the Caesar
cipher because it is a:
A) Symmetric block cipher
B) Polyalphabetic substitution cipher
C) Transposition cipher
D) Asymmetric key stream cipher
Correct Answer: B
Rationale: The Vigenère cipher uses a repeating
keyword to change the shift value across
successive letters. Because a single plaintext
letter can map to multiple ciphertext letters
depending on its position, it is a polyalphabetic
substitution cipher that flattens standard single-
letter frequency spikes.
Q3. Under what conditions is a One-Time Pad
(OTP) mathematically unbreakable (information-
theoretic security)?
A) The key is at least 128 bits long and generated by
an approved software PRNG.
B) The key is truly random, as long as or longer than
the plaintext, used only once, and kept completely
,secret.
C) The key is shared securely using an RSA 2048-
bit key exchange.
D) The ciphertext undergoes at least 16 rounds of
substitution and permutation.
Correct Answer: B
Rationale: Claude Shannon proved that a One-
Time Pad achieves perfect secrecy only when
the key is completely random, equal to or greater
than the message length, never reused in whole
or in part, and completely protected from
disclosure.
Q4. An attacker is attempting to break a
historical cipher. They possess both the
plaintext and the corresponding ciphertext for
several historical messages. What type of
cryptographic attack is this?
A) Ciphertext-only attack
B) Known-plaintext attack
C) Chosen-plaintext attack
D) Chosen-ciphertext attack
Correct Answer: B
Rationale: In a known-plaintext attack (KPA), the
cryptanalyst has access to the ciphertext and its
corresponding plaintext. They use this
, information to deduce the secret key or the
algorithm's underlying logic.
Q5. What fundamental cryptographic design
feature allowed Alan Turing and the team at
Bletchley Park to exploit and break the German
Enigma rotor machine?
A) The machine could never encrypt a letter as itself.
B) The machine relied on a completely public key
distribution system.
C) The rotors only spun backward during decryption.
D) The plugboard was limited to exactly three
physical wires.
Correct Answer: A
Rationale: A key design flaw of the Enigma
machine was its reflector mechanism, which
prevented any letter from ever mapping to itself
in the ciphertext. This predictability allowed
codebreakers to eliminate thousands of invalid
key configurations instantly using "cribs."
Q6. If an alphabet substitution cipher shifts
every letter by 3 positions (e.g., A becomes D),
what is the specific name of this historical
cipher?
