Blockchain Technology Cryptography in Blockchain 2

Question 1

What is a Merkle tree used for in blockchain?

Accepted Answer

Efficiently verifying the integrity of transaction sets

Answer

A Merkle tree hashes pairs of transactions recursively, producing a single root hash that lets nodes verify any transaction without downloading the full block.

Question 2

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

Accepted Answer

Collision resistance

Answer

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

Question 3

In Elliptic Curve Cryptography (ECC), the 'discrete logarithm problem' refers to the difficulty of:

Accepted Answer

Finding the scalar k given the points k·G and G on the curve

Answer

Given the public point k·G and base point G, recovering the private scalar k is computationally infeasible, forming the security basis of ECC.

Question 4

What does the 'r' component of an ECDSA signature represent?

Accepted Answer

The x-coordinate of a random point on the elliptic curve

Answer

In ECDSA, a random nonce k is chosen, and r is the x-coordinate of the point k·G modulo the curve order.

Question 5

Why is nonce reuse catastrophic in ECDSA?

Accepted Answer

It allows an attacker to compute the private key from two signatures

Answer

If the same nonce k is used for two different messages, the private key can be algebraically derived from the two signature pairs.

Blockchain Practice Test

Blockchain Practice Test

Blockchain Technology Cryptography in Blockchain 2