CBCP Cryptography and Security Questions and Answers

Question 1

In public-key cryptography as used in blockchain, what is the primary function of the private key?

Accepted Answer

To encrypt the hash of a transaction, creating a digital signature.

Answer

The private key is used to create a digital signature by encrypting the hash of a transaction's data. This signature serves as proof that the transaction was authorized by the owner of the private key, ensuring authenticity and non-repudiation. Anyone with the corresponding public key can then verify this signature.

Question 2

A malicious actor gains control of a large number of nodes on a blockchain network by creating multiple fake identities. They then use this influence to isolate a genuine node from the rest of the network, feeding it false information. What type of attack is this?

Accepted Answer

Sybil Attack

Answer

A Sybil attack involves a single entity creating and controlling numerous fake identities (nodes) within a peer-to-peer network to gain a disproportionately large influence. This control can then be used to carry out other attacks, such as an eclipse attack where a specific node is isolated from the true network.

Question 3

Which cryptographic technique allows for computations to be performed on encrypted data without decrypting it first, offering enhanced privacy for smart contracts and blockchain analytics?

Accepted Answer

Homomorphic Encryption

Answer

Homomorphic encryption is a specific form of encryption that allows computations to be performed directly on ciphertext. The result of the computation, when decrypted, is the same as if the operations had been performed on the plaintext, making it ideal for privacy-preserving computations on a transparent ledger.

Question 4

A user wants to prove they have a sufficient account balance to enter a decentralized lottery without revealing their actual balance or transaction history. Which cryptographic method is best suited for this scenario?

Accepted Answer

Zero-Knowledge Proof (ZKP)

Answer

A Zero-Knowledge Proof (ZKP) is a cryptographic protocol that allows a 'prover' to prove to a 'verifier' that a statement is true, without revealing any information beyond the validity of the statement itself. This is perfect for privacy-focused applications where specific facts need to be verified without disclosing the underlying sensitive data.

Question 5

Compared to the RSA algorithm, what is the primary advantage of using Elliptic Curve Cryptography (ECC) for generating key pairs in blockchain systems like Bitcoin and Ethereum?

Accepted Answer

It provides the same level of security with significantly smaller key sizes.

Answer

The main advantage of ECC over RSA is its efficiency. ECC can provide the same level of cryptographic security as RSA but with much smaller key sizes. For example, a 256-bit ECC key offers comparable security to a 3072-bit RSA key, which leads to lower computational overhead and faster processing, crucial for blockchain performance.

CBCP - Certified Blockchain Professional Practice Test

CBCP - Certified Blockchain Professional Practice Test

CBCP Cryptography and Security Questions and Answers