WGU C839 INTRO TO CRYPTOGRAPHY 2025 OA
PREPARATION TEST BANK WITH 300 REAL EXAM
QUESTIONS AND CORRECT VERIFIED ANSWERS
GRADED A+/ C839 PREP FOR OA AND PRE-
ASSESSMENT
What type of encryption uses different keys to encrypt and decrypt the message?
A Symmetric
B Private key
C Secure
D Asymmetric
D
The most widely used asymmetric encryption algorithm is what?
A RSA
B Vigenere
C DES
D Caesar Cipher
A
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)
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)
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)
B Electronic codebook (ECB)
C Output feedback (OFB)
D Cipher-block chaining (CBC)
C
Which of the following modes can be used to turn a block cipher into a stream cipher?
A Propagating cipher-block chaining (PCBC) and Electronic codebook (ECB)
B Counter Mode (CTR) and Propagating cipher-block chaining (PCBC)
C Electronic codebook (ECB) and Output feedback (OFB)
D Output feedback (OFB) and Counter Mode (CTR)
D
A fixed-size pseudorandom number that is fed into a symmetric cipher to increase randomness is
called what?
A IV
B Key
C Chain
D Salt
,A
A number that is used only one time then discarded is called what?
A Nonce
B Chain
C Salt
D IV
A
Which of the following is a stream cipher that uses variable length key from 1 to 256 bytes?
A RC4
B AES
C DESx
D DES
A
This algorithm was published by the German engineering firm Seimans in 1993. It is a software based
stream cipher using Lagged Fibonacci generator along with a concept borrowed from the shrinking
generator ciphers.
A RC4
B Blowfish
C FISH
D Twofish
C
Which of the following is NOT required for a hash?
A Minimum key length of 256 bits
B Variable-length input, fixed-length output
, C Non-reversible
D Few collisions
A
A ______ refers to a situation where two different inputs yield the same output.
A Substitution
B Convergence
C Collision
D Transposition
C
What is a salt?
A Key rotation
B Random bits intermixed with a hash to increase randomness and reduce collisions.
C Random bits intermixed with a symmetric cipher to increase randomness and make it more
secure.
D Key whitening
B
RFC 1321 describes what hash?
A RIPEMD
B SHA1
C GOST
D MD5
D
PREPARATION TEST BANK WITH 300 REAL EXAM
QUESTIONS AND CORRECT VERIFIED ANSWERS
GRADED A+/ C839 PREP FOR OA AND PRE-
ASSESSMENT
What type of encryption uses different keys to encrypt and decrypt the message?
A Symmetric
B Private key
C Secure
D Asymmetric
D
The most widely used asymmetric encryption algorithm is what?
A RSA
B Vigenere
C DES
D Caesar Cipher
A
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)
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)
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)
B Electronic codebook (ECB)
C Output feedback (OFB)
D Cipher-block chaining (CBC)
C
Which of the following modes can be used to turn a block cipher into a stream cipher?
A Propagating cipher-block chaining (PCBC) and Electronic codebook (ECB)
B Counter Mode (CTR) and Propagating cipher-block chaining (PCBC)
C Electronic codebook (ECB) and Output feedback (OFB)
D Output feedback (OFB) and Counter Mode (CTR)
D
A fixed-size pseudorandom number that is fed into a symmetric cipher to increase randomness is
called what?
A IV
B Key
C Chain
D Salt
,A
A number that is used only one time then discarded is called what?
A Nonce
B Chain
C Salt
D IV
A
Which of the following is a stream cipher that uses variable length key from 1 to 256 bytes?
A RC4
B AES
C DESx
D DES
A
This algorithm was published by the German engineering firm Seimans in 1993. It is a software based
stream cipher using Lagged Fibonacci generator along with a concept borrowed from the shrinking
generator ciphers.
A RC4
B Blowfish
C FISH
D Twofish
C
Which of the following is NOT required for a hash?
A Minimum key length of 256 bits
B Variable-length input, fixed-length output
, C Non-reversible
D Few collisions
A
A ______ refers to a situation where two different inputs yield the same output.
A Substitution
B Convergence
C Collision
D Transposition
C
What is a salt?
A Key rotation
B Random bits intermixed with a hash to increase randomness and reduce collisions.
C Random bits intermixed with a symmetric cipher to increase randomness and make it more
secure.
D Key whitening
B
RFC 1321 describes what hash?
A RIPEMD
B SHA1
C GOST
D MD5
D
