Cryptography Flashcards
7 cards from real CBCP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Cryptography flashcards as text
What is the purpose of a Verifiable Random Function (VRF) in blockchain consensus protocols?
Answer: To produce a pseudorandom output with a cryptographic proof that the output was computed correctly
A VRF generates a random output along with a proof that anyone can verify was computed correctly from the given input and private key, enabling unpredictable but verifiable leader election.
What does it mean for a cryptographic protocol to be 'computationally secure' versus 'information-theoretically secure'?
Answer: Computationally secure protocols are safe assuming bounded adversary compute power; information-theoretically secure ones are safe against unlimited compute
Information-theoretic security (like a one-time pad) is unbreakable regardless of compute power, while computational security assumes adversaries cannot solve hard mathematical problems within feasible time.
In a ring signature scheme used by privacy coins like Monero, what is concealed?
Answer: The identity of the actual signer among a group of possible signers
Ring signatures allow a signer to produce a signature on behalf of a group, making it cryptographically indistinguishable which group member actually signed.
What is the role of a hash pointer in a blockchain data structure?
Answer: It links each block to the previous one by including both the hash and location of prior data, enabling tamper detection
A hash pointer stores both the address of previous data and its cryptographic hash, so any tampering with historical data invalidates all subsequent hash pointers.
What does 'homomorphic encryption' allow that conventional encryption does not?
Answer: Computation on encrypted data such that the result, when decrypted, matches the result of the same computation on plaintext
Homomorphic encryption lets a third party (e.g., a blockchain node) perform operations on ciphertexts and return an encrypted result without ever seeing the plaintext.
What is the cryptographic weakness exploited by a 'length extension attack' against hash functions?
Answer: For Merkle-Damgård constructions, knowing H(m) lets an attacker compute H(m‖extra) without knowing m
Merkle-Damgård hash functions (like SHA-1 and SHA-256) are vulnerable to length extension: given H(m), an attacker can compute H(m‖padding‖suffix) for any chosen suffix.
What is the primary advantage of BLS (Boneh-Lynn-Shacham) signatures over ECDSA in blockchain validator systems?
Answer: Multiple BLS signatures can be aggregated into a single compact signature, reducing bandwidth and verification cost
BLS signature aggregation allows thousands of validator signatures to be combined into one signature of constant size, dramatically reducing the data validators must exchange and nodes must verify.