WGU C839 Introduction to Cryptography: Exam Practice Questions With Correct Answers | Updated Graded A+

Messages are encrypted using different secrets, and the analyst compares the messages to figure out how the algorithm works. - ANSWER Which technique does related-key cryptanalysis use to decipher a message? Steganography - ANSWER Which type of cryptography is being used when the author uses secret inks? Payload - ANSWER What is the hidden message in a steganographic communication? By substituting each letter for the letter from the opposite end of the alphabet (i.e. A becomes Z, B becomes Y, etc.) - ANSWER How did the ATBASH cipher work? 2 to the 56th power - ANSWER DES has a key space of what? 128/192/256 - ANSWER Which of the following are valid key sizes for AES (choose three)? 3DES - ANSWER Which of the following algorithms uses three different keys to encrypt the plain text? Block Cipher - ANSWER AES is what type of cipher? Asymmetric - ANSWER 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? RSA - ANSWER Which of the following is an asymmetric cipher? The algorithm(s) needed to encrypt and decrypt a message - ANSWER A cipher is defined as what Symmetric systems - ANSWER AES is what type of system? Joan's public key - ANSWER John is going to use RSA to encrypt a message to Joan. What key should he use? They are faster - ANSWER What advantage do symmetric algorithms have over asymmetric algorithms Larger key sizes increase security - ANSWER Which of the following is generally true about key sizes? Hash - ANSWER A _____ is a function and is not reversible. Diffie-Hellman (DH)/Menezes-Qu-Vanstone (MQV)/Elliptic-curve Diffie-Hellman (ECDH) - ANSWER What are protocols for exchanging keys? AES - ANSWER Which of the following would be the fastest: RSA/AES/DH/EC DES - ANSWER Which of the following would be the weakest encryption algorithm? RSA/AES/DES/EC 256 - ANSWER What is the largest key size that AES can use? AES - ANSWER All of the following are key exchange protocols except for____ DH/AES/MQV/ECDH RSA - ANSWER What encryption algorithm relies on the inability to factor large prime numbers? Letter/word frequency is maintained - ANSWER Using substitution without transposition leads to what weakness? Skipjack - ANSWER What algorithm does the clipper chip use? 80 bit - ANSWER What size key does Skipjack use? 64 - ANSWER What size block does Skipjack use? The message is divided into blocks and each block is encrypted separately. This is the most basic mode for symmetric encryption. - ANSWER With Electronic codebook (ECB) what happens Skipjack - ANSWER Which algorithm implements an unbalanced Feistel cipher? Each block of plaintext is XORed with the previous ciphertext block before being encrypted - ANSWER With Cipher-block chaining (CBC) what happens? The ciphertext block is encrypted then the ciphertext produced is XOR'd back with the plaintext to produce the current ciphertext block. - ANSWER With Cipher feedback (CFB) what happens? 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 - ANSWER What does Output feedback (OFB) do? CTR/OFB - ANSWER What modes cannot be used to turn a block cipher into a stream cipher? (select 2) A fixed size random stream that is added to a block cipher to increase randomness. - ANSWER What is an initialization vector (IV)? Nonce - ANSWER A number that is used only one time, then discarded is called what? 256 bits - ANSWER What is the largest key size that RC4 can use? The Lagged Fibonacci generator - ANSWER What is the basis for the FISH algorithm? Variable length input, fixed length output/Few collisions/Not reversible - ANSWER What is required for a hash? RSA - ANSWER Which of the following is used to encrypt email and create digital signatures? AES/SHA1/RSA/DES A collision - ANSWER 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? Salt - ANSWER 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 MD5 - ANSWER 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. FORK256 - ANSWER 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