Page 1 of 107
WGU C839 Introductory Cryptography
Objective Assessment Exam A, B & Practice
Test – Complete 500 Questions with Verified
Detailed Answers, Recently Released
Official Exam Overview:
The WGU C839 OA evaluates learners’ understanding of foundational cryptography concepts,
including encryption methods, cryptographic modes, hashing, and key management. The exam
emphasizes both theory and application, requiring learners to identify encryption techniques,
explain block cipher operations, and implement cryptographic solutions to secure digital
information in practical IT environments.
Exam Coverage Areas:
• Symmetric encryption algorithms and block cipher modes
• Asymmetric encryption and key pair concepts
• Hash functions and message integrity verification
• Key generation, management, and distribution
• Cryptographic protocols for secure communication
• Applications of encryption in networks and systems
• Security best practices and mitigation of common threats
QUESTION 1:
With _______, the message is divided into blocks and each block is encrypted separately. This is the
most basic mode for symmetric encryption.
A) Electronic Codebook (ECB) ✅
B) Cipher-Block Chaining (CBC)
C) Cipher Feedback (CFB)
D) Output Feedback (OFB)
Rationale:
ECB encrypts each block independently, making it the simplest mode. Identical plaintext blocks
produce identical ciphertext blocks, which can reveal patterns.
QUESTION 2:
Which symmetric encryption mode links each ciphertext block to the previous block to enhance
security?
A) ECB
B) CBC ✅
,C) CFB
D) OFB
Rationale:
Cipher-Block Chaining (CBC) uses previous ciphertext blocks in encrypting the current block,
reducing pattern vulnerability compared to ECB.
QUESTION 3:
Which mode is suitable for streaming data because it encrypts information bit by bit or byte by
byte?
A) ECB
B) CBC
C) CFB ✅
D) OFB
Rationale:
CFB (Cipher Feedback) allows incremental encryption, making it ideal for continuous data
streams.
QUESTION 4:
Which symmetric encryption mode generates a keystream independent of plaintext and XORs it with
the message?
A) ECB
B) CBC
C) CFB
D) OFB ✅
Rationale:
OFB (Output Feedback) produces a keystream unrelated to plaintext, which is XORed with the
message to generate ciphertext, improving error tolerance.
QUESTION 5:
What is a major weakness of ECB mode?
A) Slower performance
B) Vulnerability to pattern analysis ✅
C) Requires multiple keys
D) Cannot encrypt binary data
Rationale:
ECB mode is susceptible to pattern recognition because identical plaintext blocks encrypt to
identical ciphertext blocks, exposing structural information.
With , the message is divided into blocks and each block is encrypted separately. This is
,the most basic mode for symmetric encryption.
A Electronic codebook (ECB)
B Cipher-block chaining (CBC)
C Cipher feedback (CFB)
D Output feedback (OFB) - ANSWER-A
Which of the following is an example of an unbalanced Feistel?
A 3DES
B Skipjack
C Twofish
D AES - ANSWER-B
1
, Page 2 of 107
This process is done by having each block of plaintext is XORed with the previous ciphertext
block before being encrypted.
A Output feedback (OFB)
B Cipher-block chaining (CBC)
C Electronic codebook (ECB)
D Cipher feedback (CFB) - ANSWER-B
The process wherein the ciphertext block is encrypted then the ciphertext produced is XOR'd
back with the plaintext to produce the current ciphertext block is called what?
A Output feedback (OFB)
B Cipher-block chaining (CBC)
C Cipher feedback (CFB)
D Electronic codebook (ECB) - ANSWER-C
This is a method for turning a block cipher into a stream cipher by generating a keystream
block, which are then XORed with the plaintext blocks to get the ciphertext.
A Cipher feedback (CFB)
2
WGU C839 Introductory Cryptography
Objective Assessment Exam A, B & Practice
Test – Complete 500 Questions with Verified
Detailed Answers, Recently Released
Official Exam Overview:
The WGU C839 OA evaluates learners’ understanding of foundational cryptography concepts,
including encryption methods, cryptographic modes, hashing, and key management. The exam
emphasizes both theory and application, requiring learners to identify encryption techniques,
explain block cipher operations, and implement cryptographic solutions to secure digital
information in practical IT environments.
Exam Coverage Areas:
• Symmetric encryption algorithms and block cipher modes
• Asymmetric encryption and key pair concepts
• Hash functions and message integrity verification
• Key generation, management, and distribution
• Cryptographic protocols for secure communication
• Applications of encryption in networks and systems
• Security best practices and mitigation of common threats
QUESTION 1:
With _______, the message is divided into blocks and each block is encrypted separately. This is the
most basic mode for symmetric encryption.
A) Electronic Codebook (ECB) ✅
B) Cipher-Block Chaining (CBC)
C) Cipher Feedback (CFB)
D) Output Feedback (OFB)
Rationale:
ECB encrypts each block independently, making it the simplest mode. Identical plaintext blocks
produce identical ciphertext blocks, which can reveal patterns.
QUESTION 2:
Which symmetric encryption mode links each ciphertext block to the previous block to enhance
security?
A) ECB
B) CBC ✅
,C) CFB
D) OFB
Rationale:
Cipher-Block Chaining (CBC) uses previous ciphertext blocks in encrypting the current block,
reducing pattern vulnerability compared to ECB.
QUESTION 3:
Which mode is suitable for streaming data because it encrypts information bit by bit or byte by
byte?
A) ECB
B) CBC
C) CFB ✅
D) OFB
Rationale:
CFB (Cipher Feedback) allows incremental encryption, making it ideal for continuous data
streams.
QUESTION 4:
Which symmetric encryption mode generates a keystream independent of plaintext and XORs it with
the message?
A) ECB
B) CBC
C) CFB
D) OFB ✅
Rationale:
OFB (Output Feedback) produces a keystream unrelated to plaintext, which is XORed with the
message to generate ciphertext, improving error tolerance.
QUESTION 5:
What is a major weakness of ECB mode?
A) Slower performance
B) Vulnerability to pattern analysis ✅
C) Requires multiple keys
D) Cannot encrypt binary data
Rationale:
ECB mode is susceptible to pattern recognition because identical plaintext blocks encrypt to
identical ciphertext blocks, exposing structural information.
With , the message is divided into blocks and each block is encrypted separately. This is
,the most basic mode for symmetric encryption.
A Electronic codebook (ECB)
B Cipher-block chaining (CBC)
C Cipher feedback (CFB)
D Output feedback (OFB) - ANSWER-A
Which of the following is an example of an unbalanced Feistel?
A 3DES
B Skipjack
C Twofish
D AES - ANSWER-B
1
, Page 2 of 107
This process is done by having each block of plaintext is XORed with the previous ciphertext
block before being encrypted.
A Output feedback (OFB)
B Cipher-block chaining (CBC)
C Electronic codebook (ECB)
D Cipher feedback (CFB) - ANSWER-B
The process wherein the ciphertext block is encrypted then the ciphertext produced is XOR'd
back with the plaintext to produce the current ciphertext block is called what?
A Output feedback (OFB)
B Cipher-block chaining (CBC)
C Cipher feedback (CFB)
D Electronic codebook (ECB) - ANSWER-C
This is a method for turning a block cipher into a stream cipher by generating a keystream
block, which are then XORed with the plaintext blocks to get the ciphertext.
A Cipher feedback (CFB)
2
