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Introduction to Cryptography Security
Quiz Chapter 01: Introduction to Cryptography Se- curity
1. Which security service ensures that information is not disclosed to unauthorized parties? A) Confidentiality B) Integrity C) Availability D) Nonrepudiation
2. Which property ensures that data has not been altered? A) Integrity B) Confidentiality C) Availability D) Authentication
3. Which service verifies the identity of a communicating party? A) Authentication B) Authorization C) Confidentiality D) Integrity
4. Nonrepudiation primarily means that
A) a sender cannot deny sending a message B) data is encrypted at rest C) data is compressed D) the key is public
5. A passive attack typically involves
A) eavesdropping on communications B) modifying messages C) injecting new messages D) deleting records
6. An active attack might include
A) modifying or injecting messages B) only listening C) only noting packet counts D) only recording timings Page 1
Introduction to Cryptography Security
7. Kerckhoffs’s principle states that security should rely on A) secrecy of the key B) secrecy of the algorithm
C) secrecy of the implementation
D) secrecy of the plaintext format
8. A one-time pad is perfectly secure when
A) the key is random, as long as the message, and never reused B) the key is short C) the key is public D) the key is reused
9. In symmetric cryptography, the encryption and decryption keys are A) the same or easily derived B) always public C) unrelated
D) published in the certificate
10. In public-key encryption, which key is used to encrypt a message to Bob? A) Bob’s public key B) Bob’s private key C) Alice’s public key D) Alice’s private key
11. The size of the key space for an n-bit key is A) 2n B) n2 C) 2n D) n!
12. Brute-force resistance increases primarily with A) key length B) ciphertext length C) plaintext redundancy D) alphabet size only 13. The Caesar cipher is a
A) monoalphabetic substitution cipher B) transposition cipher Page 2
Introduction to Cryptography Security C) polyalphabetic cipher D) stream cipher
14. A transposition cipher works by
A) rearranging symbol positions B) substituting symbols C) XORing with a keystream D) multiplying by a matrix
15. Frequency analysis is most effective against A) simple substitution ciphers B) one-time pads C) modern block ciphers D) random permutations
16. Confusion in cipher design aims to
A) obscure the relationship between key and ciphertext
B) increase plaintext redundancy C) reduce ciphertext size D) eliminate keys
17. Diffusion in cipher design aims to
A) spread plaintext influence over many ciphertext bits B) reduce key size C) make keys public D) eliminate S-boxes
18. In a known-plaintext attack, the attacker has access to
A) plaintext and corresponding ciphertext pairs B) only ciphertexts C) only plaintexts D) the private key
19. In a chosen-plaintext attack, the attacker can
A) obtain ciphertexts for plaintexts of their choice B) decrypt any ciphertext C) choose keys D) modify the algorithm
20. In a chosen-ciphertext attack, the attacker can Page 3
Introduction to Cryptography Security
A) obtain plaintexts for chosen ciphertexts B) choose the key length C) read the key directly D) only observe ciphertexts
21. A ciphertext-only attack means the attacker has A) only ciphertexts B) plaintexts and ciphertexts C) the secret key D) the algorithm is hidden
22. A major drawback of symmetric encryption is
A) secure key distribution between parties B) slow performance C) large ciphertext expansion D) lack of confidentiality
23. Public-key cryptography helps solve A) key distribution B) data compression C) error correction D) routing
24. A hash function is primarily used to A) detect changes to data B) encrypt data C) compress data for storage
D) generate random keys directly
25. A MAC differs from a hash because it A) uses a secret key B) is always reversible C) is public by design D) guarantees confidentiality
26. Which security service is NOT provided by a digital signature alone? A) Confidentiality B) Integrity C) Authentication Page 4
Introduction to Cryptography Security D) Nonrepudiation
27. Computational security means an attack is
A) infeasible with available resources B) impossible in principle
C) prevented by secrecy of algorithms
D) valid only for short messages
28. Information-theoretic security means
A) security holds even with unlimited computation
B) security holds only for short keys C) the algorithm is secret D) the plaintext is random
29. In cryptography examples, Alice and Bob usually represent
A) the legitimate communicating parties B) attackers C) certification authorities D) network routers
30. The name commonly given to an eavesdropper is A) Eve B) Mallory C) Trent D) Peggy
31. A cryptographic protocol specifies
A) how parties use primitives to achieve a security goal B) only the key length C) only the cipher algorithm D) only file formats
32. Redundancy in plaintext generally makes cryptanalysis A) easier B) impossible C) irrelevant D) always slower
33. A good cryptographic key should be A) random and kept secret Page 5
Introduction to Cryptography Security B) short and public C) reused across systems D) derived from usernames
34. The main goal of encryption is to provide A) confidentiality B) availability C) compression D) error detection
35. Integrity and authentication are often achieved by A) MACs or digital signatures B) block sizes C) data compression D) routing protocols
36. Which of the following is a symmetric cipher? A) AES B) RSA C) Diffie-Hellman D) DSA
37. Which of the following is an asymmetric scheme? A) RSA B) DES C) AES D) RC4 38. Cryptanalysis refers to
A) breaking cryptographic systems B) implementing protocols C) compressing data D) generating keys only 39. Cryptology is the study of
A) cryptography and cryptanalysis B) only encryption C) only decryption D) only number theory Page 6
Introduction to Cryptography Security
40. In practice, a common security parameter is A) key length B) message length C) alphabet size D) file name length Page 7