WGU C839 – Introduction to
Cryptography (2025/2026)
Questions With 100% Correct
Answers
What type of encryption uses different keys to encrypt and decrypt the message?
A Symmetric
B Private key
C Secure
D Asymmetric - Answer D
The most widely used asymmetric encryption algorithm is what?
A RSA
B Vigenere
C DES
D Caesar Cipher - Answer A
Original, unencrypted information is referred to as .
A text
B plaintext
C cleantext
D ciphertext - Answer B
Which of the following is NOT an asymmetric system?
A PGP
B RSA
C SSL
D DES - Answer D
In order for User A to send User B an encrypted message that only User B can read,
User A must encrypt message with which of the following keys?
A User A's public key
B User A's private key
C User B's public key
D User B's private key - Answer C
The greatest weakness with symmetric algorithms is .
A They are less secure than asymmetric
B The problem of key exchange
C They are slower than asymmetric
D The problem of generating keys - Answer B
,Which of the following is generally true about block sizes?
A Smaller block sizes increase security
B Block sizes must be more than 256 bits to be secure
C Block size is irrelevant to security
D Larger block sizes increase security - Answer D
A is a function that takes a variable-size input m and returns a fixed-size
string.
A Symmetric cipher
B Hash
C Asymmetric cipher
D Feistel - Answer B
Which of the following is a cryptographic protocol that allows two parties to establish
a shared key over an insecure channel?
A Elliptic Curve
B RSA
C MD5
D Diffie-Hellman - Answer D
A is a digital representation of information that identifies you as a
relevant entity by a trusted third party?
A Digital Signature
B Hash
C Ownership stamp
D Digest - Answer A
What is the standard used by most digital certificates?
A X.509
B CRL
C RFC 2298
D OCSP - Answer A
DES uses keys of what size?
A 56 bits
B 192 bits
C 128 bits
D 64 bits - Answer A
Which of the following is NOT a key size used by AES?
A 512 bits
B 128 bits
C 192 bits
,D 256 bits - Answer A
Which of the following was a multi alphabet cipher widely used from the 16th century
(1553) to the early 20th century (1900s)?
A Vigenere
B Caesar
C Atbash
D Scytale - Answer A
Which of the following is a substitution cipher used by ancient Hebrew scholars?
A Caesar
B Vigenere
C Scytale
D Atbash - Answer D
Shifting each letter in the alphabet a fixed number of spaces to the right or left is an
example of what?
A Bit shifting
B Confusion
C Multi substitution
D Single substitution - Answer D
Which of the following most accurately defines encryption?
A changing a message so it can only be easily read by the intended recipient
B Making binary changes to a message to conceal it
C changing a message using complex mathematics
D Applying keys to plain text - Answer A
If you use substitution alone, what weakness is present in the resulting cipher text?
A It is the same length as the original text
B It is easily broken with modern computers.
C It is too simple.
D Because it maintains letter and word frequency. - Answer D
uses at least two different shifts, changing the shift with different letters in the
plain text.
A Atbash
B multi-alphabet encryption
C Scytale
D Caesar cipher - Answer B
, was designed to provide built in cryptography for the clipper chip.
A Blowfish
B Skipjack
C GOST
D 3DES - Answer B
Which of the following uses an 80 bit key on 64 bit blocks?
A Twofish
B AES
C Skipjack
D DES - Answer C
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
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.
Cryptography (2025/2026)
Questions With 100% Correct
Answers
What type of encryption uses different keys to encrypt and decrypt the message?
A Symmetric
B Private key
C Secure
D Asymmetric - Answer D
The most widely used asymmetric encryption algorithm is what?
A RSA
B Vigenere
C DES
D Caesar Cipher - Answer A
Original, unencrypted information is referred to as .
A text
B plaintext
C cleantext
D ciphertext - Answer B
Which of the following is NOT an asymmetric system?
A PGP
B RSA
C SSL
D DES - Answer D
In order for User A to send User B an encrypted message that only User B can read,
User A must encrypt message with which of the following keys?
A User A's public key
B User A's private key
C User B's public key
D User B's private key - Answer C
The greatest weakness with symmetric algorithms is .
A They are less secure than asymmetric
B The problem of key exchange
C They are slower than asymmetric
D The problem of generating keys - Answer B
,Which of the following is generally true about block sizes?
A Smaller block sizes increase security
B Block sizes must be more than 256 bits to be secure
C Block size is irrelevant to security
D Larger block sizes increase security - Answer D
A is a function that takes a variable-size input m and returns a fixed-size
string.
A Symmetric cipher
B Hash
C Asymmetric cipher
D Feistel - Answer B
Which of the following is a cryptographic protocol that allows two parties to establish
a shared key over an insecure channel?
A Elliptic Curve
B RSA
C MD5
D Diffie-Hellman - Answer D
A is a digital representation of information that identifies you as a
relevant entity by a trusted third party?
A Digital Signature
B Hash
C Ownership stamp
D Digest - Answer A
What is the standard used by most digital certificates?
A X.509
B CRL
C RFC 2298
D OCSP - Answer A
DES uses keys of what size?
A 56 bits
B 192 bits
C 128 bits
D 64 bits - Answer A
Which of the following is NOT a key size used by AES?
A 512 bits
B 128 bits
C 192 bits
,D 256 bits - Answer A
Which of the following was a multi alphabet cipher widely used from the 16th century
(1553) to the early 20th century (1900s)?
A Vigenere
B Caesar
C Atbash
D Scytale - Answer A
Which of the following is a substitution cipher used by ancient Hebrew scholars?
A Caesar
B Vigenere
C Scytale
D Atbash - Answer D
Shifting each letter in the alphabet a fixed number of spaces to the right or left is an
example of what?
A Bit shifting
B Confusion
C Multi substitution
D Single substitution - Answer D
Which of the following most accurately defines encryption?
A changing a message so it can only be easily read by the intended recipient
B Making binary changes to a message to conceal it
C changing a message using complex mathematics
D Applying keys to plain text - Answer A
If you use substitution alone, what weakness is present in the resulting cipher text?
A It is the same length as the original text
B It is easily broken with modern computers.
C It is too simple.
D Because it maintains letter and word frequency. - Answer D
uses at least two different shifts, changing the shift with different letters in the
plain text.
A Atbash
B multi-alphabet encryption
C Scytale
D Caesar cipher - Answer B
, was designed to provide built in cryptography for the clipper chip.
A Blowfish
B Skipjack
C GOST
D 3DES - Answer B
Which of the following uses an 80 bit key on 64 bit blocks?
A Twofish
B AES
C Skipjack
D DES - Answer C
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
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.
