CBCP Cryptography 2

Question 1

Which elliptic curve is used by Bitcoin for its digital signature scheme?

Accepted Answer

secp256k1

Answer

Bitcoin uses the secp256k1 elliptic curve defined in the SEC standard for its ECDSA signature scheme.

Question 2

What property ensures that a cryptographic hash function cannot be reversed to find the original input?

Accepted Answer

Pre-image resistance

Answer

Pre-image resistance means it is computationally infeasible to find an input that produces a given hash output.

Question 3

In Ethereum's signature scheme, what is the purpose of the 'v' value returned alongside r and s?

Accepted Answer

It allows recovery of the public key from the signature

Answer

The 'v' recovery identifier allows the verifier to reconstruct the public key directly from the signature and message hash.

Question 4

What is a Merkle proof used for in blockchain systems?

Accepted Answer

Proving a transaction is included in a block without downloading the full block

Answer

A Merkle proof provides a compact set of hashes that allows a lightweight client to verify inclusion of a transaction in a Merkle tree.

Question 5

Which type of encryption scheme does Diffie-Hellman key exchange establish?

Accepted Answer

A shared symmetric key over an insecure channel

Answer

Diffie-Hellman allows two parties to derive a shared symmetric secret over a public channel without ever transmitting the secret itself.

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