WGU D830 OA INTRODUCTION TO CRYPTOGRAPHY
EXAM PREP 2026-2027: QUESTIONS & CORRECT
ANSWERS WITH RATIONALES GRADED A+
50 QUESTIONS
TABLE OF CONTENTS
# TOPIC
1 Analyze and compare symmetric and asymmetric cryptographic algorithms and their appropriate use
cases
2 Evaluate the security properties of hash functions, MACs, and digital signatures against various attack
models
3 Apply key management principles, including key exchange, storage, and rotation, in secure system
design
4 Identify and mitigate common cryptographic vulnerabilities in protocols and implementations
5 WGU D830 OA Introduction to Cryptography Exam Prep 2026
6 2027
7 Questions & Correct Answers with Rationales Graded A+
8 Foundations of Cryptography and Information Security
9 Applied Cryptography and Information Security
10 Advanced Cryptography and Information Security
11 Cryptography and Information Security Review
ABSTRACT
This study document brings together 50 carefully worded exam questions drawn from WGU D830
OA Introduction to Cryptography Exam Prep 2026-2027: Questions & Correct Answers with
Rationales Graded A+, with the strongest emphasis placed on Analyze and compare symmetric
and asymmetric cryptographic algorithms and their appropriate use cases, Evaluate the security
properties of hash functions, MACs, and digital signatures against various attack models, Apply
key management principles, including key exchange, storage, and rotation and in secure system
design. Every item follows the wording style and level of reasoning you meet in the real paper, and
each one is paired with a clear rationale so the correct choice is never a guess. Work through the
set at your own pace, mark the questions that slow you down, then come back to them until the
reasoning feels automatic. Learners who revise this way walk into the exam room recognising the
pattern behind the questions instead of meeting them for the first time. Keep going - steady, honest
practice is what turns a difficult paper into a comfortable pass.
Page 1
,Q1 ANALYZE AND COMPARE SYMMETRIC AND ASYMMETRIC CRYPTOGRAPHIC
ALGORITHMS AND THEIR APPROPRIATE USE CASES
A security architect must choose a mode of operation for encrypting a large disk
volume. The mode must provide confidentiality and allow random read/write
access to any block without requiring decryption of preceding blocks. Which
mode is most appropriate?
A. Cipher Block Chaining (CBC)
B. Counter (CTR) mode CORRECT
C. Electronic Codebook (ECB)
D. Cipher Feedback (CFB) mode
RATIONALE: CTR mode turns a block cipher into a stream cipher, allowing random access to
any block by computing the counter for that block, and it is parallelizable. CBC and CFB require
sequential decryption from the previous block, and ECB is insecure for large data due to pattern
leakage. Thus, CTR is the correct choice for random access disk encryption.
Q2 ANALYZE AND COMPARE SYMMETRIC AND ASYMMETRIC CRYPTOGRAPHIC
ALGORITHMS AND THEIR APPROPRIATE USE CASES
In the context of the RSA cryptosystem, which of the following conditions is both
necessary and sufficient to ensure that the public exponent e is valid for
encryption?
A. e must be a prime number greater than 2.
B. e must be relatively prime to (n). CORRECT
C. e must be less than n.
D. e must be a generator of the multiplicative group modulo n.
RATIONALE: For RSA, e must be coprime to (n) = (p-1)(q-1) to guarantee that a modular inverse
d exists, making decryption possible. e need not be prime (e.g., 3, 17, 65537 are common but not
all prime), and while e < n is typical, it is not strictly required for correctness. Being a generator is
not necessary; e only needs to be invertible modulo (n).
Page 2
, Q3 ANALYZE AND COMPARE SYMMETRIC AND ASYMMETRIC CRYPTOGRAPHIC
ALGORITHMS AND THEIR APPROPRIATE USE CASES
A developer uses HMAC-SHA256 to authenticate messages but accidentally
reuses the same secret key for both HMAC and as the encryption key in AES-CBC.
What is the primary security risk of this key reuse?
A. It enables a padding oracle attack on the encryption.
B. It allows a related-key attack that breaks both primitives.
C. It may violate the cryptographic separation of duties, potentially leading to cross-protocol
attacks. CORRECT
D. It reduces the effective key length of HMAC to 128 bits.
RATIONALE: Using the same key for encryption and authentication violates the principle of key
separation, which can enable cross-protocol attacks where weaknesses in one primitive
compromise the other. Padding oracle attacks (A) do not directly result from key reuse,
related-key attacks (B) are not generally applicable here, and key length reduction (D) is not a
consequence. Thus, the main risk is the lack of domain separation.
Q4 ANALYZE AND COMPARE SYMMETRIC AND ASYMMETRIC CRYPTOGRAPHIC
ALGORITHMS AND THEIR APPROPRIATE USE CASES
Which of the following best describes the security property provided by a
cryptographic hash function that makes it suitable for storing password verifiers?
A. Collision resistance
B. Preimage resistance CORRECT
C. Second preimage resistance
D. Pseudorandomness
RATIONALE: Preimage resistance ensures that given a hash output, it is computationally
infeasible to find any input that hashes to that output, which protects passwords from being
reversed. Collision resistance and second preimage resistance are important for other
applications like digital signatures but are not the primary property for password storage.
Pseudorandomness is not a standard security property for this purpose.
Page 3
EXAM PREP 2026-2027: QUESTIONS & CORRECT
ANSWERS WITH RATIONALES GRADED A+
50 QUESTIONS
TABLE OF CONTENTS
# TOPIC
1 Analyze and compare symmetric and asymmetric cryptographic algorithms and their appropriate use
cases
2 Evaluate the security properties of hash functions, MACs, and digital signatures against various attack
models
3 Apply key management principles, including key exchange, storage, and rotation, in secure system
design
4 Identify and mitigate common cryptographic vulnerabilities in protocols and implementations
5 WGU D830 OA Introduction to Cryptography Exam Prep 2026
6 2027
7 Questions & Correct Answers with Rationales Graded A+
8 Foundations of Cryptography and Information Security
9 Applied Cryptography and Information Security
10 Advanced Cryptography and Information Security
11 Cryptography and Information Security Review
ABSTRACT
This study document brings together 50 carefully worded exam questions drawn from WGU D830
OA Introduction to Cryptography Exam Prep 2026-2027: Questions & Correct Answers with
Rationales Graded A+, with the strongest emphasis placed on Analyze and compare symmetric
and asymmetric cryptographic algorithms and their appropriate use cases, Evaluate the security
properties of hash functions, MACs, and digital signatures against various attack models, Apply
key management principles, including key exchange, storage, and rotation and in secure system
design. Every item follows the wording style and level of reasoning you meet in the real paper, and
each one is paired with a clear rationale so the correct choice is never a guess. Work through the
set at your own pace, mark the questions that slow you down, then come back to them until the
reasoning feels automatic. Learners who revise this way walk into the exam room recognising the
pattern behind the questions instead of meeting them for the first time. Keep going - steady, honest
practice is what turns a difficult paper into a comfortable pass.
Page 1
,Q1 ANALYZE AND COMPARE SYMMETRIC AND ASYMMETRIC CRYPTOGRAPHIC
ALGORITHMS AND THEIR APPROPRIATE USE CASES
A security architect must choose a mode of operation for encrypting a large disk
volume. The mode must provide confidentiality and allow random read/write
access to any block without requiring decryption of preceding blocks. Which
mode is most appropriate?
A. Cipher Block Chaining (CBC)
B. Counter (CTR) mode CORRECT
C. Electronic Codebook (ECB)
D. Cipher Feedback (CFB) mode
RATIONALE: CTR mode turns a block cipher into a stream cipher, allowing random access to
any block by computing the counter for that block, and it is parallelizable. CBC and CFB require
sequential decryption from the previous block, and ECB is insecure for large data due to pattern
leakage. Thus, CTR is the correct choice for random access disk encryption.
Q2 ANALYZE AND COMPARE SYMMETRIC AND ASYMMETRIC CRYPTOGRAPHIC
ALGORITHMS AND THEIR APPROPRIATE USE CASES
In the context of the RSA cryptosystem, which of the following conditions is both
necessary and sufficient to ensure that the public exponent e is valid for
encryption?
A. e must be a prime number greater than 2.
B. e must be relatively prime to (n). CORRECT
C. e must be less than n.
D. e must be a generator of the multiplicative group modulo n.
RATIONALE: For RSA, e must be coprime to (n) = (p-1)(q-1) to guarantee that a modular inverse
d exists, making decryption possible. e need not be prime (e.g., 3, 17, 65537 are common but not
all prime), and while e < n is typical, it is not strictly required for correctness. Being a generator is
not necessary; e only needs to be invertible modulo (n).
Page 2
, Q3 ANALYZE AND COMPARE SYMMETRIC AND ASYMMETRIC CRYPTOGRAPHIC
ALGORITHMS AND THEIR APPROPRIATE USE CASES
A developer uses HMAC-SHA256 to authenticate messages but accidentally
reuses the same secret key for both HMAC and as the encryption key in AES-CBC.
What is the primary security risk of this key reuse?
A. It enables a padding oracle attack on the encryption.
B. It allows a related-key attack that breaks both primitives.
C. It may violate the cryptographic separation of duties, potentially leading to cross-protocol
attacks. CORRECT
D. It reduces the effective key length of HMAC to 128 bits.
RATIONALE: Using the same key for encryption and authentication violates the principle of key
separation, which can enable cross-protocol attacks where weaknesses in one primitive
compromise the other. Padding oracle attacks (A) do not directly result from key reuse,
related-key attacks (B) are not generally applicable here, and key length reduction (D) is not a
consequence. Thus, the main risk is the lack of domain separation.
Q4 ANALYZE AND COMPARE SYMMETRIC AND ASYMMETRIC CRYPTOGRAPHIC
ALGORITHMS AND THEIR APPROPRIATE USE CASES
Which of the following best describes the security property provided by a
cryptographic hash function that makes it suitable for storing password verifiers?
A. Collision resistance
B. Preimage resistance CORRECT
C. Second preimage resistance
D. Pseudorandomness
RATIONALE: Preimage resistance ensures that given a hash output, it is computationally
infeasible to find any input that hashes to that output, which protects passwords from being
reversed. Collision resistance and second preimage resistance are important for other
applications like digital signatures but are not the primary property for password storage.
Pseudorandomness is not a standard security property for this purpose.
Page 3
