Free Blockchain Security Training Cryptographic Security Principles Questions and Answers

Question 1

Which property of a cryptographic hash function ensures that it is computationally infeasible to find two different inputs that produce the same hash output?

Accepted Answer

Collision resistance

Answer

Collision resistance is the property that makes it computationally infeasible to find any two distinct inputs, x and y, such that H(x) = H(y). This is critical in blockchains to prevent malicious actors from creating a fraudulent transaction or block that has the same hash as a legitimate one.

Question 2

Alice wants to send 1 Ether to Bob. She constructs a transaction and uses her private key to sign it. What is the primary cryptographic guarantee that this digital signature provides to the network?

Accepted Answer

The transaction was authentically created by the owner of Alice's public address and has not been altered.

Answer

A digital signature in a blockchain transaction provides two key guarantees: authenticity (the transaction was created by the holder of the private key corresponding to the public address) and integrity (the transaction data has not been tampered with since it was signed). It does not provide confidentiality, as transaction data is public.

Question 3

Which of the following cryptographic components, essential to most current blockchain systems, is most directly threatened by the development of large-scale quantum computers running Shor's algorithm?

Accepted Answer

Elliptic Curve Digital Signature Algorithm (ECDSA) used for transaction signing.

Answer

Shor's algorithm is specifically designed to efficiently solve the discrete logarithm problem and integer factorization. The security of ECDSA is based on the difficulty of the elliptic curve discrete logarithm problem (ECDLP). A sufficiently powerful quantum computer running Shor's algorithm could derive a private key from a public key, breaking ECDSA. Hashing algorithms like SHA-256 are considered more resistant, though their security is somewhat weakened by Grover's algorithm, not Shor's.

Question 4

A blockchain application needs to verify that a user is over 18 without the user having to reveal their actual birthdate. Which cryptographic principle is best suited for this task?

Accepted Answer

Zero-Knowledge Proofs (ZKPs)

Answer

Zero-Knowledge Proofs (ZKPs) allow a 'prover' to prove to a 'verifier' that a statement is true (e.g., "I am over 18") without revealing any information beyond the validity of the statement itself. This is the exact use case described, preserving the user's privacy by not disclosing the underlying data (their birthdate).

Question 5

What is the primary advantage of using Elliptic Curve Cryptography (ECC) for digital signatures in blockchain systems compared to older algorithms like RSA?

Accepted Answer

It offers significantly smaller key sizes for the same level of security.

Answer

The main advantage of ECC is its efficiency. It provides the same level of cryptographic security as RSA but with much smaller key sizes. For example, a 256-bit ECC key is roughly equivalent in strength to a 3072-bit RSA key. This is crucial for blockchains, where smaller signatures and public keys reduce transaction size and save valuable block space.

Blockchain Practice Test

Blockchain Practice Test

Free Blockchain Security Training Cryptographic Security Principles Questions and Answers