Bitcoin Blockchain Architecture and Network Transactions BFC Practice Questions (Page 9)

Questions 41–45

1. 41application · medium

   A developer is building a Bitcoin transaction and needs to reference a specific UTXO as an input. Which information is required to identify the UTXO?

   • AThe transaction ID (txid) and the output index (vout) of the previous transaction.
   • BThe block height and the timestamp when the UTXO was created.
   • CThe Bitcoin address and the private key associated with the UTXO.
   • DThe scriptPubKey and the amount of the UTXO.
   Reveal Solution Discussion Select an answer first
2. 42expert · hard

   A security researcher is analyzing a potential 51% attack on a small bitcoin-like network. The attacker controls 55% of the network's hash rate. Which action is the attacker able to perform?

   • APrevent any new transactions from being created.
   • BChange the block reward to any value they want.
   • CReverse confirmed transactions and double-spend coins.
   • DSteal bitcoins from addresses by altering the UTXO set.
   Reveal Solution Discussion Select an answer first
4. 43application · medium

   A developer is creating a Bitcoin transaction that spends a UTXO locked with a P2SH script. What is required in the unlocking script?

   • AThe private key of the address that received the UTXO.
   • BThe full scriptPubKey of the previous transaction.
   • CA single signature from the owner of the UTXO.
   • DA redeem script that matches the hash in the locking script, plus data that satisfies the redeem script's conditions.
   Reveal Solution Discussion Select an answer first
5. 44expert · hard

   A bitcoin exchange is considering supporting a new hard fork that will increase the block size. What is the most critical risk they must manage?

   • AThe hard fork may create a chain split, and the exchange must decide which chain to support to avoid accepting invalid deposits.
   • BThe hard fork will reduce the block reward, making mining unprofitable.
   • CThe hard fork will require all users to upgrade their wallets immediately or lose their funds.
   • DThe hard fork will make all existing transactions invalid.
   Reveal Solution Discussion Select an answer first
6. 45expert · hard

   A malicious user attempts to double-spend by broadcasting two conflicting transactions that spend the same UTXO. The first transaction has a low fee and is broadcast widely; the second has a higher fee. What is the most likely outcome?

   • AThe network will reject both transactions to prevent fraud.
   • BBoth transactions will be confirmed in different blocks, allowing the double-spend.
   • CMiners will include the higher-fee transaction in a block, and the lower-fee transaction will be rejected as invalid.
   • DThe lower-fee transaction will be confirmed first because it was broadcast earlier.
   Reveal Solution Discussion Select an answer first