WGU D334 / D830 — Introduction to Cryptography | Questions & Answers (v1 & v2 2026 Update)
covering Foundations, Symmetric & Asymmetric Encryption, Hash Functions, Digital
Signatures, Key Management, TLS, Attacks, Post-Quantum Cryptography, and
Advanced Topics
# Question Answer
Unit 1: Foundations of Cryptography
1 What is cryptography? Cryptography is the science of securing
information by transforming it into an unreadable
format using mathematical algorithms, so only
authorized parties can read it.
2 What is the difference Cryptography is the study of creating secure
between cryptography, communication systems. Cryptanalysis is the
cryptanalysis, and study of breaking those systems. Cryptology is
cryptology? the broader field encompassing both.
3 What is plaintext? Plaintext (or cleartext) is the original, readable
data or message before it is encrypted.
4 What is ciphertext? Ciphertext is the scrambled, unreadable output
produced after encrypting plaintext using a cipher
and a key.
5 What is a cipher? A cipher is an algorithm used to perform
encryption and decryption, transforming plaintext
into ciphertext and vice versa.
6 What is encryption? Encryption is the process of converting plaintext
into ciphertext using a cipher and a key, making
the data unreadable to unauthorized parties.
7 What is decryption? Decryption is the process of converting ciphertext
back into plaintext using the appropriate key and
cipher.
Page | Study Guide for WGU Cryptography Course
,WGU D334 / D830 — Introduction to Cryptography | Questions & Answers (v1 & v2 2026 Update)
# Question Answer
8 What are the three Confidentiality (keeping data secret), Integrity
core security goals (ensuring data is not altered), and Availability
that cryptography (ensuring data is accessible to authorized users).
supports (CIA Triad)?
9 What is a A cryptographic key is a piece of secret
cryptographic key? information (a string of bits) that is used by a
cipher algorithm to encrypt or decrypt data.
10 What is Kerckhoffs's Kerckhoffs's Principle states that a cryptosystem
Principle? should be secure even if everything about the
system—except the key—is public knowledge.
11 What is 'security Security through obscurity relies on keeping the
through obscurity' and algorithm itself secret for security. It is weak
why is it considered because if the algorithm is discovered, all security
weak? is lost. Kerckhoffs's Principle argues security
should rely only on key secrecy.
12 What is a substitution A substitution cipher replaces each character (or
cipher? group of characters) in the plaintext with another
character or group, according to a defined rule or
key.
13 What is a transposition A transposition cipher rearranges the positions of
cipher? characters in the plaintext without changing the
characters themselves.
14 What is the Caesar The Caesar cipher is a simple substitution cipher
cipher? that shifts each letter in the plaintext by a fixed
number of positions in the alphabet (e.g., a shift
of 3 maps A→D, B→E).
15 What is the Vigenère The Vigenère cipher is a polyalphabetic
cipher? substitution cipher that uses a keyword to
determine different shift values for each character
in the plaintext, making it harder to break than a
simple Caesar cipher.
16 What is frequency Frequency analysis is a cryptanalytic technique
analysis? that exploits the fact that certain letters or
patterns occur more frequently in a language,
allowing an attacker to guess the substitution
mapping in classical ciphers.
Page | Study Guide for WGU Cryptography Course
,WGU D334 / D830 — Introduction to Cryptography | Questions & Answers (v1 & v2 2026 Update)
# Question Answer
17 What is the one-time The one-time pad is a theoretically unbreakable
pad (OTP)? cipher that XORs plaintext with a truly random
key of the same length, used only once. It
provides perfect secrecy if the key is truly random
and never reused.
18 Why is the one-time The key must be as long as the message,
pad impractical for completely random, and securely shared in
general use? advance—making it logistically impractical for
most real-world applications.
19 What does 'perfect Perfect secrecy means that ciphertext provides
secrecy' mean? absolutely no information about the plaintext,
regardless of the attacker's computational power.
The one-time pad achieves this.
20 What is a brute-force A brute-force attack tries every possible key until
attack? the correct one is found. Its feasibility depends on
the key size—larger keys make brute-force
computationally infeasible.
21 What is confusion in Confusion obscures the relationship between the
cryptography? plaintext, key, and ciphertext, typically achieved
through substitution operations.
22 What is diffusion in Diffusion spreads the influence of each plaintext
cryptography? bit over many ciphertext bits (and vice versa),
typically achieved through
permutation/transposition operations.
23 What is the difference A stream cipher encrypts data one bit or byte at a
between a stream time using a keystream. A block cipher encrypts
cipher and a block data in fixed-size blocks (e.g., 64-bit or 128-bit
cipher? blocks) using a key.
24 What is a A cryptographic protocol is a set of rules and
cryptographic procedures that define how cryptographic
protocol? algorithms are used to achieve security goals like
authentication, key exchange, or secure
communication.
25 What is non- Non-repudiation ensures that a sender cannot
repudiation in deny having sent a message. Digital signatures
cryptography? provide non-repudiation by cryptographically
binding a message to the sender's private key.
Page | Study Guide for WGU Cryptography Course
, WGU D334 / D830 — Introduction to Cryptography | Questions & Answers (v1 & v2 2026 Update)
# Question Answer
Unit 2: Symmetric Encryption
26 What is symmetric Symmetric encryption (also called secret-key
encryption? encryption) uses the same key for both
encryption and decryption. Both parties must
securely share this key.
27 What are the main It is fast and computationally efficient, making it
advantages of suitable for encrypting large amounts of data.
symmetric encryption?
28 What is the main Key distribution is the major problem—both
disadvantage of parties must securely exchange the shared key
symmetric encryption? before communication, which is challenging over
insecure channels.
29 What is DES (Data DES is a symmetric block cipher that encrypts 64-
Encryption Standard)? bit blocks using a 56-bit key. It was the U.S.
federal standard from 1977 but is now considered
insecure due to its short key length.
30 Why is DES DES uses only a 56-bit key, making it vulnerable
considered insecure to brute-force attacks. Modern hardware can
today? crack DES in hours.
31 What is Triple DES 3DES applies the DES algorithm three times to
(3DES)? each data block (Encrypt-Decrypt-Encrypt with up
to three different keys), increasing effective key
length to 112 or 168 bits.
32 What is AES AES is a symmetric block cipher that replaced
(Advanced Encryption DES as the U.S. standard. It supports key sizes
Standard)? of 128, 192, or 256 bits and operates on 128-bit
blocks. It is considered highly secure.
33 What algorithm is AES AES is based on the Rijndael cipher, designed by
based on? Belgian cryptographers Joan Daemen and
Vincent Rijmen.
34 What are the AES key AES-128 uses 10 rounds, AES-192 uses 12
sizes and rounds, and AES-256 uses 14 rounds of
corresponding number encryption.
of rounds?
35 What are the four SubBytes (substitution), ShiftRows
operations performed (transposition), MixColumns (mixing), and
in each AES round? AddRoundKey (XOR with round key).
Page | Study Guide for WGU Cryptography Course
covering Foundations, Symmetric & Asymmetric Encryption, Hash Functions, Digital
Signatures, Key Management, TLS, Attacks, Post-Quantum Cryptography, and
Advanced Topics
# Question Answer
Unit 1: Foundations of Cryptography
1 What is cryptography? Cryptography is the science of securing
information by transforming it into an unreadable
format using mathematical algorithms, so only
authorized parties can read it.
2 What is the difference Cryptography is the study of creating secure
between cryptography, communication systems. Cryptanalysis is the
cryptanalysis, and study of breaking those systems. Cryptology is
cryptology? the broader field encompassing both.
3 What is plaintext? Plaintext (or cleartext) is the original, readable
data or message before it is encrypted.
4 What is ciphertext? Ciphertext is the scrambled, unreadable output
produced after encrypting plaintext using a cipher
and a key.
5 What is a cipher? A cipher is an algorithm used to perform
encryption and decryption, transforming plaintext
into ciphertext and vice versa.
6 What is encryption? Encryption is the process of converting plaintext
into ciphertext using a cipher and a key, making
the data unreadable to unauthorized parties.
7 What is decryption? Decryption is the process of converting ciphertext
back into plaintext using the appropriate key and
cipher.
Page | Study Guide for WGU Cryptography Course
,WGU D334 / D830 — Introduction to Cryptography | Questions & Answers (v1 & v2 2026 Update)
# Question Answer
8 What are the three Confidentiality (keeping data secret), Integrity
core security goals (ensuring data is not altered), and Availability
that cryptography (ensuring data is accessible to authorized users).
supports (CIA Triad)?
9 What is a A cryptographic key is a piece of secret
cryptographic key? information (a string of bits) that is used by a
cipher algorithm to encrypt or decrypt data.
10 What is Kerckhoffs's Kerckhoffs's Principle states that a cryptosystem
Principle? should be secure even if everything about the
system—except the key—is public knowledge.
11 What is 'security Security through obscurity relies on keeping the
through obscurity' and algorithm itself secret for security. It is weak
why is it considered because if the algorithm is discovered, all security
weak? is lost. Kerckhoffs's Principle argues security
should rely only on key secrecy.
12 What is a substitution A substitution cipher replaces each character (or
cipher? group of characters) in the plaintext with another
character or group, according to a defined rule or
key.
13 What is a transposition A transposition cipher rearranges the positions of
cipher? characters in the plaintext without changing the
characters themselves.
14 What is the Caesar The Caesar cipher is a simple substitution cipher
cipher? that shifts each letter in the plaintext by a fixed
number of positions in the alphabet (e.g., a shift
of 3 maps A→D, B→E).
15 What is the Vigenère The Vigenère cipher is a polyalphabetic
cipher? substitution cipher that uses a keyword to
determine different shift values for each character
in the plaintext, making it harder to break than a
simple Caesar cipher.
16 What is frequency Frequency analysis is a cryptanalytic technique
analysis? that exploits the fact that certain letters or
patterns occur more frequently in a language,
allowing an attacker to guess the substitution
mapping in classical ciphers.
Page | Study Guide for WGU Cryptography Course
,WGU D334 / D830 — Introduction to Cryptography | Questions & Answers (v1 & v2 2026 Update)
# Question Answer
17 What is the one-time The one-time pad is a theoretically unbreakable
pad (OTP)? cipher that XORs plaintext with a truly random
key of the same length, used only once. It
provides perfect secrecy if the key is truly random
and never reused.
18 Why is the one-time The key must be as long as the message,
pad impractical for completely random, and securely shared in
general use? advance—making it logistically impractical for
most real-world applications.
19 What does 'perfect Perfect secrecy means that ciphertext provides
secrecy' mean? absolutely no information about the plaintext,
regardless of the attacker's computational power.
The one-time pad achieves this.
20 What is a brute-force A brute-force attack tries every possible key until
attack? the correct one is found. Its feasibility depends on
the key size—larger keys make brute-force
computationally infeasible.
21 What is confusion in Confusion obscures the relationship between the
cryptography? plaintext, key, and ciphertext, typically achieved
through substitution operations.
22 What is diffusion in Diffusion spreads the influence of each plaintext
cryptography? bit over many ciphertext bits (and vice versa),
typically achieved through
permutation/transposition operations.
23 What is the difference A stream cipher encrypts data one bit or byte at a
between a stream time using a keystream. A block cipher encrypts
cipher and a block data in fixed-size blocks (e.g., 64-bit or 128-bit
cipher? blocks) using a key.
24 What is a A cryptographic protocol is a set of rules and
cryptographic procedures that define how cryptographic
protocol? algorithms are used to achieve security goals like
authentication, key exchange, or secure
communication.
25 What is non- Non-repudiation ensures that a sender cannot
repudiation in deny having sent a message. Digital signatures
cryptography? provide non-repudiation by cryptographically
binding a message to the sender's private key.
Page | Study Guide for WGU Cryptography Course
, WGU D334 / D830 — Introduction to Cryptography | Questions & Answers (v1 & v2 2026 Update)
# Question Answer
Unit 2: Symmetric Encryption
26 What is symmetric Symmetric encryption (also called secret-key
encryption? encryption) uses the same key for both
encryption and decryption. Both parties must
securely share this key.
27 What are the main It is fast and computationally efficient, making it
advantages of suitable for encrypting large amounts of data.
symmetric encryption?
28 What is the main Key distribution is the major problem—both
disadvantage of parties must securely exchange the shared key
symmetric encryption? before communication, which is challenging over
insecure channels.
29 What is DES (Data DES is a symmetric block cipher that encrypts 64-
Encryption Standard)? bit blocks using a 56-bit key. It was the U.S.
federal standard from 1977 but is now considered
insecure due to its short key length.
30 Why is DES DES uses only a 56-bit key, making it vulnerable
considered insecure to brute-force attacks. Modern hardware can
today? crack DES in hours.
31 What is Triple DES 3DES applies the DES algorithm three times to
(3DES)? each data block (Encrypt-Decrypt-Encrypt with up
to three different keys), increasing effective key
length to 112 or 168 bits.
32 What is AES AES is a symmetric block cipher that replaced
(Advanced Encryption DES as the U.S. standard. It supports key sizes
Standard)? of 128, 192, or 256 bits and operates on 128-bit
blocks. It is considered highly secure.
33 What algorithm is AES AES is based on the Rijndael cipher, designed by
based on? Belgian cryptographers Joan Daemen and
Vincent Rijmen.
34 What are the AES key AES-128 uses 10 rounds, AES-192 uses 12
sizes and rounds, and AES-256 uses 14 rounds of
corresponding number encryption.
of rounds?
35 What are the four SubBytes (substitution), ShiftRows
operations performed (transposition), MixColumns (mixing), and
in each AES round? AddRoundKey (XOR with round key).
Page | Study Guide for WGU Cryptography Course
