Bitcoin Blockchain Architecture BBLC Practice Questions (Page 8)

Questions 36–40

1. 36foundation · easy

   How does Bitcoin's decentralization contribute to censorship resistance?

   • ABecause no single entity controls the network, it is difficult for any authority to block or reverse transactions
   • BBecause transactions are stored on a single secure server
   • CBecause the network is operated by a consortium of governments
   • DBecause all transactions are encrypted, making them invisible to authorities
   Reveal Solution Discussion Select an answer first
2. 37application · medium

   A user attempts to send 2 BTC but has only two UTXOs: one of 1.5 BTC and one of 0.4 BTC. The wallet constructs a transaction with both inputs. What is the minimum amount of change output the wallet must create?

   • AThe transaction is invalid because the total input value (1.9 BTC) is less than the intended output (2 BTC).
   • B0 BTC, because the wallet can spend exactly 1.9 BTC and the transaction is invalid.
   • C0.1 BTC, because the wallet must create a change output to avoid overpaying.
   • D0 BTC, because the wallet can add a third input from a change address to make up the difference.
   Reveal Solution Discussion Select an answer first
4. 38foundation · easy

   Why is it computationally infeasible to alter a historical block in the Bitcoin blockchain?

   • ABecause the blockchain is stored on a single immutable server
   • BBecause each block's hash depends on the previous block's hash, so changing a block would require re-mining all subsequent blocks
   • CBecause all blocks are encrypted with a secret key held by the network
   • DBecause transactions are signed with the sender's private key
   Reveal Solution Discussion Select an answer first
5. 39application · medium

   A startup wants to build a payment verification service that can confirm Bitcoin transactions quickly without downloading the entire blockchain. Which type of node should the startup operate to achieve this goal while still maintaining a reasonable level of security?

   • AA lightweight (SPV) node that downloads block headers and requests proof-of-inclusion from full nodes.
   • BA mining node that only stores the most recent 100 blocks and discards older data.
   • CA pruned full node that stores only unspent transaction outputs and no block headers.
   • DA full node that downloads and validates every block and transaction since the genesis block.
   Reveal Solution Discussion Select an answer first
6. 40expert · hard

   A developer proposes a soft fork that would make certain previously valid transactions invalid. The developer argues that this is safer than a hard fork because it is backward-compatible. Which scenario best illustrates a potential risk of this soft fork?

   • ANew nodes will reject old blocks, causing the network to split immediately.
   • BThe soft fork will change the block reward, which is not allowed by the protocol.
   • COld nodes that do not upgrade will still accept blocks containing the newly-invalid transactions, potentially causing them to follow a chain that new nodes reject.
   • DThe soft fork will require all nodes to upgrade, which is more disruptive than a hard fork.
   Reveal Solution Discussion Select an answer first