Unit 4: Message integrity and Hash function - Practice Quiz

1 What does message integrity ensure?

2 Which technique is commonly used to check message integrity?

3 What is the output of a cryptographic hash function commonly called?

4 What does message authentication primarily verify?

5 Which mechanism uses a shared secret key to authenticate a message?

6 A digital signature can provide message authentication and what other property?

7 Which key is normally used to create a digital signature?

8 What is the main idea of an iterated hash function?

9 What component is repeatedly applied in an iterated hash function?

10 What does an iterated hash function usually produce regardless of message length?

11 In an iterated hash function, what is usually processed first?

12 What type of algorithm is Whirlpool?

13 What is the output size of the Whirlpool hash function?

14 Whirlpool is based on a design related to which type of operation?

15 What is the digest length produced by SHA-512?

16 What is the word size used by SHA-512?

17 What is the message block size used by SHA-512?

18 SHA-512 belongs to which family of hash algorithms?

19 What does MD commonly represent in names such as MD4 and MD5?

20 What is the digest size of MD5?

21 A software vendor publishes a file and its SHA-512 digest on the same unsecured website. An attacker can modify both. What security property is missing?

22 Two records produce the same digest under a hash function, although their contents differ. Which hash property has failed for these records?

23 A receiver recomputes the hash of a message and obtains the expected value from a trusted source. What can the receiver reasonably conclude?

24 Alice and Bob share a secret key and use HMAC on every message. Which pair of properties does a valid HMAC primarily provide?

25 A protocol sends H(K || M) as an authentication tag, where K is secret and M is attacker-controlled. Why is HMAC generally preferred?

26 Bob verifies a MAC created with a key shared only by Alice and Bob. Why does this MAC not provide strong nonrepudiation?

27 An API authenticates requests with a valid MAC but accepts an old authenticated payment request again. Which additional mechanism most directly prevents this replay?

28 In a Merkle-Damgard-style iterated hash, what is passed from one message-block operation to the next?

29 Why does standard padding for many iterated hashes include an encoding of the original message length?

30 A Merkle-Damgard hash has an -bit chaining value. Ignoring structural weaknesses, approximately how many hash evaluations are expected to find a collision?

31 An attacker knows H(M) and the length of M for a vulnerable Merkle-Damgard hash. What may a length-extension attack allow the attacker to compute?

32 Whirlpool processes a message using 512-bit blocks and produces a 512-bit digest. Which statement correctly compares these sizes?

33 Whirlpool's internal transformation was designed using principles similar to which well-known type of primitive?

34 Under an ideal-hash assumption, what is the approximate generic collision-security level of Whirlpool's 512-bit output?

35 A system stores a SHA-512 digest in hexadecimal. How many hexadecimal characters are required, excluding prefixes or separators?

36 SHA-512 is used to hash a message whose padded form contains three 1024-bit blocks. How many times is its compression function applied?

37 Which internal word size is used by SHA-512 for its main arithmetic and logical operations?

38 A legacy application uses MD5 to detect deliberate tampering by an adversary. What is the main reason to replace it?

39 MD5 outputs 128 bits, while MD4 also outputs 128 bits. Why is equal digest length insufficient to claim equal security?

40 A database stores MD5(password) for every user without salts. Which attack is made especially practical when many users choose the same password?

41 An attacker is given a specific message and its digest , then attempts to construct a different message such that . Which security property is directly being attacked?

42 Assuming an ideal -bit hash, approximately how many independently chosen messages are required for a probability of finding at least one collision?

43 A software distributor publishes a file and its SHA-512 digest on the same unauthenticated server. An active attacker can modify both responses. Which conclusion is correct?

44 A system authenticates messages using , where is a Merkle–Damgård hash and has a guessable length. Which forgery is enabled by length extension?

45 Why does standard HMAC resist the ordinary length-extension attack that affects ?

46 A zero-IV CBC-MAC is used without length binding. For one-block messages and , their tags are and . Which two-block message has the valid tag ?

47 For an ideal -bit Merkle–Damgård hash, Joux's multicollision technique constructs equal-length messages with the same digest. What is its approximate compression-function cost?

48 Which statement correctly describes the effect of Merkle–Damgård strengthening, where the encoded message length is included in the padding?

49 Consider Davies–Meyer compression , where is a block cipher under key . For a chosen , which value is an efficiently computable fixed point satisfying ?

50 Let be Whirlpool's previous chaining value and the next message block. Which equation represents its Miyaguchi–Preneel compression step?

51 Which structural description correctly matches the final Whirlpool specification?

52 Whirlpool appends one bit, then zero bits, and finally a -bit length field. If the original message length is , what is the minimum value of ?

53 SHA-512 appends one bit, zero bits, and a -bit length field. If the original message length satisfies , how many zero bits are appended?

54 Which recurrence correctly generates SHA-512 message-schedule words for , with all additions modulo ?

55 For SHA-512's Boolean functions, let . What are and , respectively?

56 Which statement correctly distinguishes standardized SHA-512/256 from simply truncating an ordinary SHA-512 digest to bits?

57 Under an idealized analysis of full SHA-512 for ordinary fixed-length messages, which combination best describes its generic security and structural behavior?

58 MD5 appends one bit, then zero bits, and finally a -bit length field. If , what is the minimum value of ?

59 Which comparison between MD4 and MD5 is accurate?

60 Which feature most clearly distinguishes MD2 from the later MD4 and MD5 designs?