Cryptography MCQ Test Quiz (90 Questions with Answers)

I’ve got a 90-question Cryptography MCQ Test Quiz that I’d like you to rewrite. The quiz starts with basic concepts and gradually moves to advanced topics, covering classical cryptography, symmetric and asymmetric cryptography, hashing, digital signatures, cryptographic protocols, and modern areas like post-quantum cryptography.

Section 1: Basics of Cryptography MCQ

1. What is the main goal of cryptography?
   a) Data compression
   b) Data visualization
   c) Data security ✅
   d) Data deletion
2. Which of the following is NOT a goal of cryptography?
   a) Confidentiality
   b) Integrity
   c) Authentication
   d) Compression ✅
3. In cryptography, plaintext refers to:
   a) Encrypted data
   b) Unencrypted original data ✅
   c) Compressed data
   d) Digital signature
4. Ciphertext is:
   a) Always in binary
   b) Human-readable
   c) The result of encryption ✅
   d) A cryptographic hash
5. Which algorithm is used for symmetric encryption?
   a) RSA
   b) DSA
   c) AES ✅
   d) ECC
6. The process of converting ciphertext back to plaintext is:
   a) Encryption
   b) Compilation
   c) Decryption ✅
   d) Obfuscation
7. A key used for both encryption and decryption is called:
   a) Public key
   b) Symmetric key ✅
   c) Private key
   d) Initialization vector
8. What is the output length of an MD5 hash?
   a) 64 bits
   b) 128 bits ✅
   c) 256 bits
   d) 512 bits
9. What is Caesar cipher?
   a) Public key cipher
   b) Substitution cipher ✅
   c) Transposition cipher
   d) Stream cipher
10. In symmetric key cryptography, both sender and receiver use:
    a) Different keys
    b) Same key ✅
    c) No key
    d) Hashing only
11. Which cryptographic algorithm uses two different keys?
    a) SHA-1
    b) DES
    c) RSA ✅
    d) AES
12. Cryptanalysis is the process of:
    a) Encryption
    b) Secure hashing
    c) Breaking a cryptographic system ✅
    d) Key distribution
13. Which is NOT a symmetric key algorithm?
    a) Blowfish
    b) RC4
    c) RSA ✅
    d) Twofish
14. Hash functions are mainly used to ensure:
    a) Confidentiality
    b) Integrity ✅
    c) Availability
    d) Non-repudiation
15. Which of the following is a stream cipher?
    a) AES
    b) DES
    c) RC4 ✅
    d) Blowfish
16. A one-time pad offers:
    a) Weak security
    b) Perfect secrecy ✅
    c) Public key encryption
    d) No encryption
17. SHA-256 produces an output of:
    a) 128 bits
    b) 160 bits
    c) 256 bits ✅
    d) 512 bits
18. Digital signatures provide:
    a) Confidentiality only
    b) Integrity and authentication ✅
    c) Availability
    d) Compression
19. Public key is used to:
    a) Decrypt in RSA
    b) Encrypt in RSA ✅
    c) Create hash
    d) Hash data
20. Private key must be:
    a) Shared with all users
    b) Publicly available
    c) Kept secret ✅
    d) Published on websites

Section 2: Cryptography Intermediate Concepts MCQ

21. What does DES stand for?
    a) Data Encryption Standard ✅
    b) Digital Encryption Scheme
    c) Direct Encryption System
    d) Distributed Encoding Standard
22. Triple DES applies the DES cipher:
    a) One time
    b) Two times
    c) Three times ✅
    d) Four times
23. RSA is named after:
    a) A government agency
    b) Its creators ✅
    c) A programming language
    d) Encryption layers
24. The main advantage of asymmetric encryption is:
    a) Faster than symmetric
    b) One key for both tasks
    c) No need to share private keys ✅
    d) None
25. In RSA, decryption is done using:
    a) Public key
    b) Private key ✅
    c) Session key
    d) IV
26. Elliptic Curve Cryptography is known for:
    a) High power usage
    b) Large keys
    c) Small key size & strong security ✅
    d) Outdated use
27. Which key exchange algorithm is widely used in SSL?
    a) RSA
    b) Diffie-Hellman ✅
    c) MD5
    d) Blowfish
28. Digital certificates are issued by:
    a) Blockchain nodes
    b) Certification Authority ✅
    c) Browsers
    d) Firewalls
29. Which mode of AES is secure for block encryption?
    a) ECB
    b) CBC ✅
    c) RCBC
    d) Static
30. Padding in cryptography is used to:
    a) Add compression
    b) Add randomness
    c) Make data fit block sizes ✅
    d) Secure keys

31. What is a primary weakness of ECB (Electronic Codebook) mode?
    a) It uses too much memory
    b) Identical plaintext blocks yield identical ciphertext blocks ✅
    c) It works only on streaming data
    d) It supports only 64-bit encryption
32. Which block cipher algorithm replaced DES as a standard?
    a) Blowfish
    b) Twofish
    c) AES ✅
    d) RC4
33. Which of the following is NOT a hashing algorithm?
    a) SHA-256
    b) MD5
    c) RC5 ✅
    d) SHA-1
34. Public-key encryption is also called:
    a) Symmetric encryption
    b) Asymmetric encryption ✅
    c) Open encryption
    d) Enigma encryption
35. A digital signature ensures:
    a) Encryption
    b) Authentication and integrity ✅
    c) Compression
    d) Compression and authentication
36. In asymmetric cryptography, the private key is used to:
    a) Encrypt data
    b) Decrypt data
    c) Sign data
    d) Both b and c ✅
37. Which of these algorithms is used for digital signatures?
    a) AES
    b) RSA ✅
    c) RC4
    d) DES
38. Which technique helps to detect if data was altered?
    a) Hashing ✅
    b) Compression
    c) Streaming
    d) Encryption
39. Which is the most secure among the following hashing algorithms?
    a) MD5
    b) SHA-1
    c) SHA-256 ✅
    d) CRC32
40. Which key exchange method uses prime number arithmetic?
    a) ECC
    b) AES
    c) Diffie-Hellman ✅
    d) DES
41. Which of the following is a block cipher?
    a) RC4
    b) DES ✅
    c) OTP
    d) SHA-256
42. Which algorithm is most vulnerable to a brute-force attack today?
    a) AES-256
    b) RSA-2048
    c) DES ✅
    d) SHA-3
43. Which of the following is not used for symmetric encryption?
    a) AES
    b) Blowfish
    c) RSA ✅
    d) DES
44. Which concept helps in making ciphertext non-repetitive for same plaintext?
    a) Plaintext padding
    b) Initialization Vector (IV) ✅
    c) Digital Signature
    d) Diffie-Hellman
45. Which of these uses a hash function and a key to verify authenticity?
    a) HMAC ✅
    b) RSA
    c) RC4
    d) OTP
46. Which algorithm is commonly used for password hashing?
    a) AES
    b) RSA
    c) bcrypt ✅
    d) DES
47. Which of the following is used for key generation in asymmetric encryption?
    a) OTP
    b) Random number generators ✅
    c) Block ciphers
    d) Stream ciphers
48. RSA algorithm depends heavily on:
    a) Discrete logarithms
    b) Integer factorization ✅
    c) Elliptic curves
    d) Hash functions
49. The size of an RSA key that is currently considered secure is:
    a) 512 bits
    b) 1024 bits
    c) 2048 bits ✅
    d) 256 bits
50. Which of these is used to prove data origin and prevent denial?
    a) Digital signature ✅
    b) Hash function
    c) OTP
    d) TLS
51. Which of the following best describes salting?
    a) Encrypting with two keys
    b) Adding randomness to hash input ✅
    c) Decrypting with IV
    d) Encrypting ciphertext
52. Which symmetric algorithm is considered outdated and insecure?
    a) AES
    b) DES ✅
    c) Blowfish
    d) ChaCha20
53. Which operation is fastest in terms of encryption/decryption?
    a) Asymmetric
    b) Symmetric ✅
    c) Hashing
    d) Digital signing
54. Which one is a cryptographic attack that analyzes cipher implementation rather than the algorithm?
    a) Chosen plaintext attack
    b) Side-channel attack ✅
    c) Replay attack
    d) Known ciphertext attack
55. Which protocol is the successor of SSL?
    a) TSL
    b) TLS ✅
    c) TSP
    d) STS
56. The digital certificate contains:
    a) Private key
    b) Public key ✅
    c) Password
    d) Hash only
57. Which encryption is best for securing large amounts of data?
    a) Asymmetric
    b) Symmetric ✅
    c) RSA
    d) ECC
58. Which cipher algorithm is based on substitution and transposition?
    a) AES ✅
    b) RSA
    c) SHA-1
    d) ECC
59. Which of the following is used in PGP for encrypting emails?
    a) RSA
    b) AES
    c) Both symmetric and asymmetric ✅
    d) MD5
60. What is key stretching?
    a) Compressing a key
    b) Weakening key strength
    c) Making a short key stronger using hash iterations ✅
    d) Using long passphrases

Section 3: Cryptography Advanced Concepts MCQ

61. What is the major threat quantum computers pose to RSA?
    a) Speed up encryption
    b) Increase key size
    c) Break RSA with Shor’s Algorithm ✅
    d) None
62. Post-quantum cryptography aims to:
    a) Use smaller keys
    b) Replace symmetric ciphers
    c) Secure against quantum attacks ✅
    d) Reduce entropy
63. Which of the following is a post-quantum candidate algorithm?
    a) RSA
    b) AES
    c) NTRU ✅
    d) DES
64. Which attack exploits the frequency of letters in ciphertext?
    a) Brute-force
    b) Replay attack
    c) Frequency analysis ✅
    d) Side-channel
65. Side-channel attacks exploit:
    a) Algorithm flaws
    b) Physical characteristics ✅
    c) Software bugs
    d) Key lengths
66. What makes a cryptographic hash function secure?
    a) It’s fast
    b) Collision resistance ✅
    c) Symmetric nature
    d) Simple output
67. What’s a rainbow table?
    a) Secure key
    b) Brute force tool
    c) Precomputed hash lookup ✅
    d) Encryption algorithm
68. Salting is used in hashing to:
    a) Speed up encryption
    b) Reduce password size
    c) Prevent rainbow table attacks ✅
    d) Improve decryption
69. Homomorphic encryption allows computation on:
    a) Plaintext
    b) Ciphertext ✅
    c) Public key
    d) Random bits
70. Zero-knowledge proofs allow:
    a) Complete decryption
    b) Leaking some information
    c) Proving knowledge without revealing info ✅
    d) Sharing both keys
71. Which property ensures a message hasn’t been changed?
    a) Confidentiality
    b) Integrity ✅
    c) Availability
    d) Obfuscation
72. A MAC (Message Authentication Code) provides:
    a) Encryption
    b) Digital signature
    c) Authentication and integrity ✅
    d) Compression
73. Which protocol is used for secure web communication?
    a) FTP
    b) HTTP
    c) HTTPS ✅
    d) SMTP
74. TLS stands for:
    a) Transport Layer Security ✅
    b) Trusted Level Scheme
    c) Total Layer Session
    d) Token Linked Security
75. The birthday attack targets:
    a) RSA
    b) Hash functions ✅
    c) Symmetric keys
    d) Public key
76. Which algorithm is no longer considered secure?
    a) AES
    b) DES ✅
    c) RSA
    d) SHA-256
77. Which function is irreversible?
    a) Decryption
    b) Hash function ✅
    c) Encryption
    d) MAC
78. Nonce stands for:
    a) New One-time Cipher Exchange ✅
    b) Never-ending Cipher
    c) Network Operation
    d) Next Order Cipher
79. A hybrid encryption system uses:
    a) Only symmetric keys
    b) Only asymmetric keys
    c) Both symmetric and asymmetric ✅
    d) Only hash
80. Quantum-safe algorithms are tested by:
    a) NSA
    b) ISO
    c) NIST ✅
    d) Google
81. SHA-3 was introduced as a successor to:
    a) MD5
    b) SHA-2 ✅
    c) SHA-1
    d) DES
82. Digital signature algorithms include:
    a) AES
    b) DSA ✅
    c) DES
    d) MD5
83. What is ciphertext stealing used for?
    a) Stealing data
    b) Padding block ciphers securely ✅
    c) Replacing IV
    d) Compressing cipher
84. Elliptic curve cryptography is considered more efficient due to:
    a) Larger keys
    b) Complex math
    c) Smaller key sizes for same security ✅
    d) Being outdated
85. What kind of cryptography does Bitcoin use?
    a) RSA
    b) ECC (Secp256k1) ✅
    c) SHA-1
    d) DES
86. Which of the following is a symmetric block cipher?
    a) AES ✅
    b) RSA
    c) ECC
    d) DSA
87. Forward secrecy ensures:
    a) Public keys expire
    b) Past sessions remain secure ✅
    c) Private key cannot be lost
    d) Data is deleted
88. An example of asymmetric key encryption is:
    a) AES
    b) DES
    c) RSA ✅
    d) RC4
89. Which is true about hashing?
    a) It’s reversible
    b) Used only in encryption
    c) Produces fixed-length output ✅
    d) Uses both keys
90. Cryptographic agility refers to:
    a) Fast decryption
    b) Supporting multiple algorithms ✅
    c) Slow hashing
    d) One-key support only