Practice Test Geeks(CBP) Certified Bitcoin Professional Practice Test
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Blockchain and Transaction Mechanics Flashcards

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  1. What does the term 'block height' refer to in the Bitcoin blockchain?

    Answer: The sequential number of a block counting from the genesis block

    Block height is the count of blocks between a given block and the genesis block (block 0), uniquely identifying the block's position in the chain.

  2. Why is it considered risky to accept a Bitcoin payment with zero confirmations?

    Answer: The transaction has not yet been included in a block and can be replaced or double-spent

    With zero confirmations the transaction only exists in the mempool and can be invalidated by a competing double-spend transaction before any miner includes it.

  3. What is a coinbase maturity rule in Bitcoin?

    Answer: Newly mined coins cannot be spent until 100 additional blocks have been added after the coinbase block

    Bitcoin requires coinbase outputs to have at least 100 confirmations (100 more blocks on top) before they can be spent, protecting against chain reorganizations.

  4. In Bitcoin script, what does OP_RETURN do?

    Answer: Marks an output as provably unspendable and can embed up to 80 bytes of arbitrary data

    OP_RETURN immediately marks the output as unspendable and allows embedding small arbitrary data on-chain; nodes can prune these from the UTXO set.

  5. What is the scriptPubKey in a Bitcoin transaction output?

    Answer: A locking script that defines the conditions under which the output can be spent

    The scriptPubKey is the locking script placed on an output; to spend it, a matching scriptSig (or witness) must satisfy its conditions.

  6. What is a Partially Signed Bitcoin Transaction (PSBT) as defined in BIP 174?

    Answer: A standard format allowing multiple parties or devices to collaboratively sign a transaction without sharing private keys

    PSBT (BIP 174) provides a portable, extensible format so hardware wallets, multisig participants, or coin-join coordinators can pass a transaction around for signing without revealing private keys.

  7. Which of the following best describes the difference between a soft fork and a hard fork in Bitcoin?

    Answer: A soft fork tightens consensus rules and is backward-compatible with old nodes; a hard fork loosens rules and is not

    Soft forks restrict valid blocks so old nodes still accept new blocks (backward-compatible); hard forks expand rules so old nodes reject new blocks, requiring all participants to upgrade.