CBP Bitcoin Transactions and Wallets 4

Question 1

What is the significance of the 'witness discount' introduced by SegWit?

Accepted Answer

Witness data is counted at one-quarter the weight of non-witness data, reducing the effective size of SegWit transactions

Answer

SegWit introduced block weight (replacing byte size), with witness data counted at 1 weight unit per byte versus 4 for non-witness data, making SegWit transactions cheaper.

Question 2

In a hierarchical deterministic (HD) wallet following BIP32, what is the 'master private key'?

Accepted Answer

The root key derived from the seed from which all child keys are derived

Answer

The BIP32 master private key is derived from the wallet seed and serves as the root of a tree from which all child and grandchild keys are deterministically generated.

Question 3

What is a 'partially signed Bitcoin transaction' (PSBT, BIP174)?

Accepted Answer

A standard format for passing transaction data between multiple signers or devices before final broadcast

Answer

PSBT (BIP174) defines a portable transaction format that allows wallets, hardware devices, and co-signers to collaboratively add signatures without sharing private keys.

Question 4

Which of the following best describes 'transaction malleability' and how SegWit addressed it?

Accepted Answer

Third parties could alter a transaction's signature data to change its TXID without invalidating it; SegWit fixed this by moving signatures out of the hashed portion

Answer

Malleability allowed signature data changes that altered the TXID; SegWit resolved this by placing signatures in a separate witness structure excluded from the TXID hash.

Question 5

What does 'dust' refer to in Bitcoin?

Accepted Answer

Very small UTXOs whose value is less than the cost to spend them in fees

Answer

Dust UTXOs are so small that the fee required to spend them exceeds their value, making them economically unspendable.

(CBP) Certified Bitcoin Professional Practice Test

(CBP) Certified Bitcoin Professional Practice Test

CBP Bitcoin Transactions and Wallets 4