Cryptocurrency Cryptography and Hashing 4

Question 1

What is the 'birthday attack' vulnerability in hashing, and why does it matter for blockchain?

Accepted Answer

A statistical attack finding hash collisions faster than brute force due to probability theory

Answer

The birthday paradox shows collisions can be found in roughly 2^(n/2) attempts rather than 2^n, so 256-bit hashes provide ~128-bit collision security.

Question 2

What is a 'commitment scheme' in cryptography as used in some blockchain protocols?

Accepted Answer

A method to commit to a value privately and reveal it verifiably later

Answer

A commitment scheme lets a party bind to a chosen value without revealing it, then later open the commitment to prove what they chose.

Question 3

How does a Merkle proof allow lightweight clients (SPV nodes) to verify a transaction?

Accepted Answer

By providing a branch of hashes from the transaction to the Merkle root without sending all transactions

Answer

A Merkle proof supplies only log2(n) hashes needed to reconstruct the path to the root, enabling transaction verification without full block data.

Question 4

What makes the Discrete Logarithm Problem (DLP) important for elliptic curve cryptography in blockchains?

Accepted Answer

It is computationally infeasible to derive a private key from a public key

Answer

The DLP hardness on elliptic curves means computing the private key from the public key is computationally infeasible with current technology.

Question 5

What does 'deterministic' mean when describing a cryptographic hash function?

Accepted Answer

The same input always produces the same output

Answer

Determinism means identical inputs always yield identical hash outputs, which is essential for consensus across blockchain nodes.

Cryptocurrency Practice Test

Cryptocurrency Practice Test

Cryptocurrency Cryptography and Hashing 4