CBSE Node and Network Security 2

Question 1

Which attack vector allows a malicious node to return false transaction data to lightweight blockchain clients that rely on SPV (Simplified Payment Verification)?

Accepted Answer

Eclipse attack

Answer

An eclipse attack isolates an SPV client by surrounding it with attacker-controlled peers, enabling the attacker to feed false block headers or transaction confirmations.

Question 2

What is the primary purpose of a blockchain node's mempool (memory pool) from a security perspective?

Accepted Answer

Holding unconfirmed transactions pending inclusion in a block

Answer

The mempool temporarily holds unconfirmed transactions; attackers can exploit it via transaction pinning or fee manipulation to delay or block legitimate transactions.

Question 3

A blockchain node operator notices abnormally high CPU usage caused by peers repeatedly requesting the same large block. Which denial-of-service technique is being used?

Accepted Answer

Bandwidth exhaustion via block re-request flooding

Answer

Flooding a node with repeated large-block requests wastes CPU and bandwidth resources, constituting a bandwidth exhaustion DoS against that node.

Question 4

Which TLS/SSL configuration weakness most directly endangers communications between blockchain node peers over an encrypted channel?

Accepted Answer

Allowing TLS 1.0 with RC4 cipher suites

Answer

TLS 1.0 with RC4 is cryptographically broken; RC4 has known biases that allow plaintext recovery, compromising the confidentiality of peer communications.

Question 5

In Ethereum's devp2p protocol, what cryptographic mechanism is used during the initial handshake to establish a shared session key between two nodes?

Accepted Answer

ECDH (Elliptic Curve Diffie-Hellman) with secp256k1

Answer

Ethereum's RLPx transport uses ECDH on secp256k1 during the auth handshake to derive a shared session key without transmitting the key directly.

(CBSE) Certified Blockchain Security Expert Practice Test

(CBSE) Certified Blockchain Security Expert Practice Test

CBSE Node and Network Security 2