WGU C839 OBJECTIVE ASSESSMENT 2 LATEST VERSIONS (VERSION A & B) 2024-2025 /WGU C839 INTRODUCTION TO CRYPTOGRAPHY OA ACTUAL EXAM QUESTIONS AND CORRECT DETAILED ANSWERS (VERIFIED ANSWERS) ALREADY GRADED A+

Which encryption standard uses the same key to encrypt and decrypt messages?

Symmetric

Which algorithm is designated as a Type 2 product by the National Security Agency (NSA)?

Skipjack

What is the most commonly used format for certificates?

X.509 v3

What is referenced to determine if a certificate has been revoked?

Certificate revocation list (CRL)

What needs to be installed on end users' computers to allow them to trust applications that have been digitally signed by the developer?

Sender's public key

Which type of certificate must be certified by an authority to verify it with other participants?

Public Certificate

What is an attribute of the Rivest Cipher 4 (RC4) algorithm?

It requires a unique nonce.

Which mode generates the key stream with a nonce and incrementing value?

Counter (CTR)

Which mode is a stream algorithm that concatenates an incrementing value with a nonce?

Counter (CTR)

Which key would an administrator use to encrypt data so only the CEO can decrypt it?

CEO's public key

What is the result of a hash function?

Digest

What is used to efficiently encrypt large files?

Symmetric encryption

An administrator needs to encrypt the following word with the Atbash cipher: security What is the correct ciphertext?

hvxfirgb

Which cryptographic algorithm has a 128-bit hash size?

Message Digest Algorithm 5 (MD5)

Which characteristic makes a hashing function suitable for use in signature schemes?

Collision resistance

Which attribute of a hashing function makes a birthday attack possible?

Partial-message collision

Which hash algorithm produces a 160-bit output value?

SHA-1

What does cipher block chaining (CBC) use with the key to encrypt subsequent blocks of plaintext?

Previous generated ciphertext

Which mode produces the same ciphertext from two identical plaintext blocks?

Electronic codebook (ECB)

Which encryption mode is least secure?

Electronic codebook (ECB)

What is the mathematical formula used for symmetric decryption?

P = E (K,C)

Which algorithm relies on factoring the product of large prime numbers?

Rivest-Shamir-Adleman

Which encryption technology is a serial combination of hashing, data compression, symmetric-key cryptography, and public key infrastructure (PKI) and can be used for encrypting texts, emails, files, and directories or for full disk encryption?

Pretty Good Privacy (PGP)

Which concept stipulates that algorithms should be openly shared and scrutinized, but keys must be absolutely secured?

Kerckhoffs's principle

Which encryption process minimizes known plaintext attacks against Advanced Encryption Standard (AES)?

Randomizing the initialization vector

What prevents a rainbow table attack during the encryption process?

Salting

Which factor increases the required number of attempts in a brute-force attack?

Larger key size

What is a vulnerability of the Data Encryption Standard (DES)?

Key length is too short.

Which block size does the Advanced Encryption Standard (AES) use?

128

Which block algorithm includes a provision for the decryption key kept in a key escrow?

Skipjack

What is the result of A|B and B|C?

A|C

How is X mod N if N = PQ represented in number theory?

( X mod P, X mod Q)

What is the outcome when using the binary AND function on 11011 and 10100?

10000

Which mode does the Fortuna algorithm use to generate random numbers?

Counter (CTR)

What is a potential weakness of a pseudo-random number generator (PRNG)?

Same state used more than once

Which key combination is used to decrypt and verify a digital signature?

Recipient's private key to decrypt and sender's public key to verify the signature

Which key is used to sign a message or a message digest?

Sender's private key

Which key does the certificate authority (CA) use to digitally sign keys that it issues?

Server's private key

What does an end user need to verify a Rivest-Shamir -Adleman (RSA) digitally signed message?

Sender's public key

What is used when creating a digital signature, using public key infrastructure (PKI)?

The private key of the person creating the message

Which feature in Wired Equivalent Privacy (WEP) provides integrity control when sending packets over a wireless network?

Cyclic redundancy check

Which feature of Wi-Fi Protected Access (WPA) increases the difficulty of attack?

Temporal Key Integrity Protocol (TKIP)

Which two concerns does the use of Counter Mode with Cipher Block Chaining Message Authentication Code Protocol (CCMP) address?

Confidentiality/Integrity

Which extension designates a file containing a password-protected private key?

.p12

Which part of the public key infrastructure (PKI) defines how a credential is used?

Certificate policy (CP)

Which part of the public key infrastructure (PKI) is used to ensure that the format for a credential can be used by anyone on the internet?

Public Key Cryptography Standards (PKCS)

Which solution is used in a Layer 2 Tunneling Protocol (L2TP) virtual private network (VPN) to secure data in transmission?

Internet Protocol Security (IPsec)

Which network-based virtual private network (VPN) prevents unauthorized logins by preventing packet retransmission?

IP security (IPsec)

Which port does Secure Socket Tunneling Protocol (SSTP) use?

Port 443

What is a common problem with using pre-shared keys (PSKs)?

Secure key exchange

What is a concern with storing long-term secrets on media or memory?

Integrity

Which cipher uses a series of ciphers based on a keyword?

Vigenère

Which substitution cipher system reverses the sequence of the alphabet?

Atbash

Which type of cipher converts a letter to a number, passes it through a mathematical function, and then converts it back to a letter?

Affine

Which technique solves polyalphabetic substitution ciphers by deducing the key length?

Kasiski's method

Which cryptanalysis technique examines ciphertext for recurring letter combinations?

Frequency analysis

Which cryptanalysis method involves a person being tricked into encrypting a set of known messages?

Chosen plaintext attack

Which technique does related-key cryptanalysis use to decipher a message?

Messages are encrypted using different secrets, and the analyst compares the messages to figure out how the algorithm works.

Which type of cryptography is being used when the author uses secret inks?

Steganography

What is the hidden message in a steganographic communication?

Payload

How did the ATBASH cipher work?

By substituting each letter for the letter from the opposite end of the alphabet (i.e. A becomes Z, B becomes Y, etc.)

DES has a key space of what?

2 to the 56th power

Which of the following are valid key sizes for AES (choose three)?

128/192/256

Which of the following algorithms uses three different keys to encrypt the plain text?

3DES

AES is what type of cipher?

Block Cipher

Which of the following is a type of encryption that has two different keys. One key can encrypt the message and the other key can only decrypt it?

Asymmetric

Which of the following is an asymmetric cipher?

RSA

A cipher is defined as what

The algorithm(s) needed to encrypt and decrypt a message

AES is what type of system?

Symmetric systems

John is going to use RSA to encrypt a message to Joan. What key should he use?

Joan's public key

What advantage do symmetric algorithms have over asymmetric algorithms

They are faster

Which of the following is generally true about key sizes?

Larger key sizes increase security

A _____ is a function and is not reversible.

Hash

What are protocols for exchanging keys?

Diffie-Hellman (DH)/Menezes-Qu-Vanstone (MQV)/Elliptic-curve Diffie-Hellman (ECDH)

Which of the following would be the fastest: RSA/AES/DH/EC

AES

Which of the following would be the weakest encryption algorithm? RSA/AES/DES/EC

DES

What is the largest key size that AES can use?

256

All of the following are key exchange protocols except for____ DH/AES/MQV/ECDH

AES

What encryption algorithm relies on the inability to factor large prime numbers?

RSA

Using substitution without transposition leads to what weakness?

Letter/word frequency is maintained

What algorithm does the clipper chip use?

Skipjack

What size key does Skipjack use?

80 bit

What size block does Skipjack use?

64

With Electronic codebook (ECB) what happens

The message is divided into blocks and each block is encrypted separately. This is the most basic mode for symmetric encryption.

Which algorithm implements an unbalanced Feistel cipher?

Skipjack

With Cipher-block chaining (CBC) what happens?

Each block of plaintext is XORed with the previous ciphertext block before being encrypted

With Cipher feedback (CFB) what happens?

The ciphertext block is encrypted then the ciphertext produced is XOR'd back with the plaintext to produce the current ciphertext block.

What does Output feedback (OFB) do?

A block cipher is converted into a stream cipher by generating a keystream blocks, which are then XORed with the plaintext blocks to get the ciphertext

What modes cannot be used to turn a block cipher into a stream cipher? (select 2)

CTR/OFB

What is an initialization vector (IV)?

A fixed size random stream that is added to a block cipher to increase randomness.

A number that is used only one time, then discarded is called what?

Nonce

What is the largest key size that RC4 can use?

256 bits

What is the basis for the FISH algorithm?

The Lagged Fibonacci generator

What is required for a hash?

Variable length input, fixed length output/Few collisions/Not reversible

Which of the following is used to encrypt email and create digital signatures? AES/SHA1/RSA/DES

RSA

Bob's password is hashed, and so is John's. Even though they used different passwords, the hash is the same. What is this called?

A collision

In relationship to hashing, the term _____refers to random bits that are used as one of the inputs to the hash. Essentially the is intermixed with the message that is to be hashed

Salt

This is a 128 bit hash that is specified by RFC 1321. It was designed by Ron Rivest in 1991 to replace an earlier hash function.

MD5

This hash function uses 512-bit blocks and implements preset constants that change after each repetition. Each block is hashed into a 256-bit block through four branches that divides each 512 block into sixteen 32-bit words that are further encrypted and rearranged

FORK256

Which of the following is an asymmetric algorithm that was first publically described in 1977?

RSA