Blockchain Technology Cryptographic Principles 5

Question 1

What is a 'hash pointer' in the context of blockchain data structures?

Accepted Answer

A data structure containing both a cryptographic hash of the previous block's data and a link to that block

Answer

A hash pointer stores the cryptographic hash of the previous block's content alongside its location, ensuring any tampering with past data invalidates subsequent hashes.

Question 2

Which attack exploits weak random number generation during ECDSA signing, potentially exposing a private key?

Accepted Answer

Nonce reuse attack (k-value reuse)

Answer

If the same nonce k is used in two different ECDSA signatures, an attacker can algebraically recover the private key from the two signatures.

Question 3

What does 'pre-image resistance' mean for a cryptographic hash function used in blockchain?

Accepted Answer

Given a hash output, it is computationally infeasible to find any input that produces it

Answer

Pre-image resistance ensures that knowing the hash output provides no practical way to reconstruct an input that would hash to that value.

Question 4

In zk-SNARKs used by privacy blockchains like Zcash, what does 'succinct' mean?

Accepted Answer

The proof size and verification time are small and constant regardless of computation size

Answer

Succinct means the proof is very short and verification is fast (often milliseconds), even if the underlying computation being proved is large.

Question 5

Which cryptographic concept underpins the security of blockchain Proof-of-Work by making it easy to verify but hard to compute?

Accepted Answer

Computational asymmetry (one-way functions)

Answer

One-way functions are easy to evaluate but practically impossible to invert, so finding a valid nonce requires enormous work while verifying it takes a single hash computation.

Blockchain Practice Test

Blockchain Practice Test

Blockchain Technology Cryptographic Principles 5