Cryptography and Hashing Flashcards

Which property of a cryptographic hash function ensures that two different inputs cannot produce the same hash output?

Answer: Collision resistance

Collision resistance guarantees that it is computationally infeasible to find two distinct inputs that hash to the same output.

In elliptic curve cryptography (ECC), what mathematical operation forms the basis of the discrete logarithm problem?

Answer: Point multiplication on a curve

ECC security relies on the difficulty of reversing point multiplication (repeated point addition) on an elliptic curve.

What is the primary role of a nonce in a Proof-of-Work blockchain hash puzzle?

Answer: To vary the input so miners can find a valid hash

Miners iterate the nonce value to change the block header input until the resulting hash meets the network's difficulty target.

Which hashing algorithm does Bitcoin use to produce its block header hash?

Answer: SHA-256 applied twice (SHA-256d)

Bitcoin applies SHA-256 twice (double SHA-256) to block headers, which provides an additional layer of security against length-extension attacks.

What does a Merkle root in a blockchain block represent?

Answer: A single hash summarizing all transactions in the block

The Merkle root is the top hash of a Merkle tree built from all transaction hashes, allowing efficient and tamper-evident verification.

Which cryptographic primitive is used in HMAC to ensure message integrity and authenticity?

Answer: A shared secret key combined with a hash function

HMAC (Hash-based Message Authentication Code) combines a secret key with a hash function to produce an authentication tag tied to both the key and message.

In the context of blockchain wallets, what does BIP-32 define?

Answer: A standard for hierarchical deterministic (HD) wallet key derivation

BIP-32 specifies how a single master seed can deterministically derive a tree of child public and private keys for HD wallets.