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- In a ciphertext-only attack, the attacker has access to:
a. plaintext only
b. ciphertext only
c. both plaintext and ciphertext
d. decryption oracle
Answer: b. ciphertext only (attacker sees only encrypted messages) (GeeksforGeeks) - A known-plaintext attack assumes the attacker knows:
a. only ciphertext
b. only plaintext
c. pairs of plaintext and corresponding ciphertext
d. decryption oracle
Answer: c. pairs of plaintext and corresponding ciphertext (GeeksforGeeks) - In a chosen-plaintext attack, the attacker can:
a. only decrypt arbitrary ciphertexts
b. choose plaintexts and obtain their ciphertexts
c. only observe ciphertexts
d. only guess keys
Answer: b. choose plaintexts and obtain their ciphertexts (Wikipedia) - In a chosen-ciphertext attack, the attacker can:
a. choose ciphertexts to be decrypted and get plaintexts
b. only choose plaintexts and get ciphertexts
c. only see ciphertexts
d. only see plaintexts
Answer: a. choose ciphertexts to be decrypted and get plaintexts (Wikipedia) - A brute-force attack attempts to break encryption by:
a. analyzing side channels
b. trying all possible keys
c. using known plaintext–ciphertext pairs
d. using downgrade protocols
Answer: b. trying all possible keys (International Security Journal) - A side-channel attack exploits:
a. mathematical weaknesses in cipher
b. implementation leakages (timing, power, EM, etc.)
c. plaintext–ciphertext pairs
d. key reuse
Answer: b. implementation leakages (timing, power, EM, etc.) (GeeksforGeeks) - A timing attack is a type of:
a. ciphertext-only attack
b. side-channel attack
c. chosen-plaintext attack
d. man-in-the-middle attack
Answer: b. side-channel attack (uses timing leakage) (GoAllSecure) - A power analysis attack is used to infer key bits by observing:
a. ciphertext
b. computing time
c. power consumption during cryptographic operations
d. plaintext
Answer: c. power consumption during cryptographic operations (GeeksforGeeks) - A bit-flipping attack allows an attacker to:
a. learn the key
b. change ciphertext to produce predictable changes in plaintext
c. decrypt arbitrary ciphertexts
d. force a downgrade in protocol
Answer: b. change ciphertext to produce predictable changes in plaintext (Wikipedia) - A padding oracle attack uses feedback about:
a. key bits
b. valid vs invalid padding responses
c. time taken to decrypt
d. ciphertext only
Answer: b. valid vs invalid padding responses (oracle) (Wikipedia) - The Meet-in-the-Middle attack is a type of:
a. side-channel attack
b. brute-force attack
c. space-time tradeoff attack
d. chosen-ciphertext attack
Answer: c. space-time tradeoff attack (applied to double encryption) (Wikipedia) - Double DES is vulnerable to meet-in-the-middle which reduces its effective security to about:
a. 2^112
b. 2^128
c. 2^57
d. 2^56
Answer: c. 2^57 operations (plus memory) (Wikipedia) - A downgrade attack forces communication to:
a. stronger encryption
b. no encryption
c. a weaker or legacy protocol version
d. side-channel mode
Answer: c. a weaker or legacy protocol version (rollback) (Wikipedia) - SSL stripping is an example of:
a. brute-force attack
b. downgrade attack
c. padding oracle attack
d. side-channel attack
Answer: b. downgrade attack (stripping HTTPS to HTTP) (professormesser.com) - A birthday attack primarily targets:
a. symmetric encryption
b. key exchange
c. hash functions (collision resistance)
d. side-channel leakages
Answer: c. hash functions (finding collisions) (Cryptography Meta Stack Exchange) - To break hash collision resistance for an n-bit hash, the expected work is about:
a. 2^n
b. 2^(n/2)
c. n^2
d. n
Answer: b. 2^(n/2) (birthday paradox) (Cryptography Meta Stack Exchange) - Rainbow table attack is used to break:
a. symmetric keys
b. public-key systems
c. passwords (hashes)
d. side-channel encryption
Answer: c. passwords (hashed) by precomputed tables
(Note: classic cryptographic-attack related) - Dictionary attack is a variant of brute-force focusing on:
a. trying all possible keys
b. trying likely passwords/keys from a list
c. side-channel leakages
d. padding oracle
Answer: b. trying likely passwords/keys from a list - A chosen-key attack allows the attacker to:
a. choose the plaintext
b. choose the cipher
c. choose the key and observe the encryption behavior
d. choose ciphertext to decrypt
Answer: c. choose the key and observe encryption (rare model) - Linear cryptanalysis is a known-plaintext attack technique used on:
a. asymmetric ciphers
b. block ciphers
c. stream ciphers
d. side-channel attacks
Answer: b. block ciphers (uses linear approximations) - Differential cryptanalysis is a chosen-plaintext attack method that studies:
a. ciphertext-only outputs
b. differences in plaintext pairs and differences in ciphertexts
c. side-channels
d. key scheduling weakness
Answer: b. differences in plaintexts and ciphertexts - Related-key attack allows attacker to:
a. fix the key
b. choose keys with a known relation (like K1, K2 differing in certain bits) and get encryptions
c. observe ciphertext only
d. side-channel leakages
Answer: b. choose keys with known relation and exploit relationships - In RSA padding oracle attack (Bleichenbacher style), the attacker exploits:
a. timing only
b. padding error responses
c. key reuse
d. hash collisions
Answer: b. padding error responses (oracle) (Wikipedia) - Lunchtime attack is a variant of:
a. chosen-plaintext attack
b. adaptive chosen-ciphertext attack
c. side-channel attack
d. downgrade attack
Answer: b. adaptive chosen-ciphertext attack (attacker can query until challenge time) (Wikipedia) - A midnight attack is synonymous with:
a. side-channel attack
b. non-adaptive chosen-ciphertext
c. lunch/midnight variant of chosen-ciphertext
d. downgrade attack
Answer: c. lunchtime / midnight variant of chosen-ciphertext (CCA variant) (Wikipedia) - Adaptive chosen-ciphertext attack (CCA2) allows attacker to:
a. adaptively submit ciphertexts both before and after challenge (except the challenge itself)
b. only submit before challenge
c. only non-adaptive decrypt queries
d. no decrypt queries
Answer: a. adaptively query before and after challenge except for challenge itself (Wikipedia) - A non-adaptive chosen-ciphertext attack (CCA1) allows attacker to:
a. query after seeing challenge
b. query only before challenge
c. no queries
d. side-channel only
Answer: b. query only before challenge (lunchtime style) (Wikipedia) - A man-in-the-middle attack (MITM) in cryptography typically intercepts and possibly alters:
a. keys only
b. communications between parties
c. side-channel leakages
d. padding oracles
Answer: b. communications between parties (intercept & relay) (CCN.com) - Replay attack involves:
a. altering ciphertext
b. reusing a prior valid message or ciphertext
c. side-channel leak
d. padding oracle
Answer: b. reusing a prior valid message or ciphertext - Social engineering / phishing is considered a cryptographic attack when:
a. the attacker mathematically breaks encryption
b. attacker convinces user to reveal keys or plaintext
c. side-channel timing is used
d. padding oracles are exploited
Answer: b. attacker convinces user to reveal keys or plaintext (not a mathematical break) (CCN.com) - The rubber-hose cryptanalysis refers to:
a. key guessing
b. side-channel
c. coercion / torture for key disclosure
d. downgrade attacks
Answer: c. coercion / torture to force reveal of keys (non-technical attack) (Check Point Research) - In ciphertext-only attack against stream cipher, the attacker might:
a. guess the key bit by bit
b. use known plaintext
c. modify ciphertext to induce errors
d. border on side-channels
Answer: a. guess the key bit by bit (if keystream reused or weak) - If two messages use same keystream in a stream cipher (key reuse), attacker can:
a. break only one message
b. XOR ciphertexts to remove keystream revealing plaintext XOR plaintext
c. nothing useful
d. side-channel leak
Answer: b. XOR ciphertexts to cancel keystream and get plaintext XOR plaintext - A hybrid attack in cryptanalysis combines:
a. brute-force and side-channel
b. chosen-plaintext and chosen-ciphertext
c. differential and linear cryptanalysis
d. man-in-the-middle and replay
Answer: a. brute-force and side-channel - Cryptographic fault attack induces faults (errors) in cryptographic computations to:
a. break padding
b. observe erroneous outputs to deduce internal state
c. downgrade
d. only side-channel
Answer: b. observe faulty outputs to deduce internal state (fault injection) - Cold boot attack targets:
a. ciphertext
b. memory residuals (RAM) to retrieve keys after reboot
c. side-channel timing
d. padding oracles
Answer: b. memory residuals (after power-off) to retrieve keys - Cache-timing attack is a side-channel attack that exploits:
a. memory reuse
b. how long memory/cache access takes
c. ciphertext-only
d. bit-flipping
Answer: b. how long memory/cache access takes (timing difference) - Electromagnetic (EM) emanation attack is a side-channel attack where attacker monitors:
a. ciphertext
b. emitted electromagnetic signals during crypto operations
c. timing only
d. padding oracles
Answer: b. EM signals emitted during operations (GeeksforGeeks) - A traffic analysis attack (in cryptographic context) is:
a. observing plaintext
b. analyzing patterns (length, frequency, timing) of ciphertext flows
c. modifying ciphertext
d. side-channel only
Answer: b. analyzing patterns of ciphertext flows (metadata) - A wrapper attack in cryptography refers to:
a. key wrap permutation attack
b. composite protocol layers attack (wrapping weaker cipher inside stronger)
c. side-channel
d. bit-flipping
Answer: b. composite protocol layers attack (wrapping weaker operations) - A rectangle attack is a variant of:
a. linear cryptanalysis
b. differential cryptanalysis
c. side-channel
d. key schedule exploit
Answer: b. differential cryptanalysis (enhanced variant) - Impossible differential attack uses:
a. impossible values in differential propagation
b. side-channel
c. brute-force only
d. chosen-ciphertext
Answer: a. differential patterns that never occur to reduce key space - Interpolation attack is effective on:
a. block ciphers with algebraic structure
b. hash functions
c. side-channel
d. stream ciphers
Answer: a. block ciphers with algebraic structure (build polynomial model) - Slide attack exploits:
a. key reuse across rounds
b. identical subkeys / same round functions
c. side-channel
d. chosen ciphertext
Answer: b. identical round function structure (sliding property) - A backdoor attack in cryptography means:
a. attacker breaks cipher mathematically
b. algorithm intentionally includes hidden weakness or trapdoor
c. side-channel
d. downgrade
Answer: b. algorithm includes hidden weakness or trapdoor - Key collision attack refers to:
a. two keys producing same ciphertext for a message
b. side-channel
c. brute-force on key space
d. downgrade
Answer: a. two keys mapping plaintext to the same ciphertext for some message - A chosen-initialization-vector (chosen-IV) attack allows attacker to:
a. pick IV and observe resulting ciphertext
b. choose plaintext
c. choose ciphertext to decrypt
d. side-channel
Answer: a. pick IV and observe ciphertext output (weak IV usage) - TSW (Three-Stage Weakness) attack is related to:
a. RSA
b. elliptic-curve cryptography
c. Feistel ciphers
d. symmetric key scheduling
Answer: b. elliptic-curve cryptography (weakness in certain curves) - Algorithmic complexity attack targets:
a. side-channel
b. worst-case performance (e.g. in hash tables / denial-of-service)
c. padding oracles
d. downgrade
Answer: b. worst-case performance to degrade security or availability - Protocol downgrade + padding oracle combination (e.g., POODLE) is an example of:
a. pure side-channel attack
b. combined attacks: downgrade + padding oracle
c. pure brute-force
d. simple man-in-the-middle
Answer: b. a combined attack leveraging downgrade and padding oracle (POODLE) (Wikipedia)
