Blockchain Cryptographic Principles Questions and Answers

Question 1

In public-key cryptography, what is the specific role of the sender's private key and the receiver's public key when creating a digital signature for a blockchain transaction?

Accepted Answer

The sender's private key signs a hash of the transaction, and the receiver's public key verifies the signature.

Answer

The sender's private key encrypts the message, and the receiver's public key decrypts it.

Answer

The sender's private key generates the transaction hash, and the receiver's public key adds it to the block.

Answer

The sender's private key encrypts the entire block, and the receiver's public key confirms the transaction.

Question 2

A developer is building a lightweight mobile wallet that needs to verify if a specific transaction is included in a block without downloading the entire blockchain. Which cryptographic structure is essential for enabling this functionality, often referred to as Simplified Payment Verification (SPV)?

Accepted Answer

Merkle Tree

Answer

Public Key Infrastructure (PKI)

Answer

Ring Signature

Answer

Symmetric Key Algorithm

Question 3

Why is Elliptic Curve Cryptography (ECC) widely preferred over RSA for generating key pairs in most modern blockchain protocols like Bitcoin and Ethereum?

Accepted Answer

ECC provides a greater level of security with significantly smaller key sizes, leading to better efficiency.

Answer

ECC keys are easier for humans to remember and transcribe.

Answer

RSA is a symmetric algorithm, whereas blockchain requires asymmetric cryptography.

Answer

ECC allows for the recovery of lost private keys, while RSA does not.

Question 4

In a Proof-of-Work (PoW) blockchain like Bitcoin, what is the primary function of a 'nonce'?

Accepted Answer

It is an arbitrary number that miners repeatedly change to find a valid block hash.

Answer

It is a user's secret password for accessing their wallet.

Answer

It represents the total number of transactions within a block.

Answer

It is the public key of the miner who successfully solves the block.

Question 5

Which of the following is NOT a core property of a cryptographic hash function used in blockchain?

Accepted Answer

Reversibility (two-way)

Answer

Pre-image resistance (one-way)

Answer

Deterministic output

Answer

Collision resistance

Question 6

A user wants to send an encrypted message to another user on a blockchain-based platform. The sender uses the receiver's public key to encrypt the message. Which key must the receiver use to decrypt the message?

Accepted Answer

The receiver's private key

Answer

The sender's public key

Answer

The sender's private key

Answer

A shared symmetric key