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Forks and Network Upgrades Flashcards

7 cards from real CBP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. What is the purpose of 'SIGHASH_NOINPUT' (proposed in BIP 118) in the context of Bitcoin upgrades?

    Answer: It allows signatures that commit to a script but not a specific UTXO, enabling more flexible payment channel protocols

    SIGHASH_NOINPUT/ANYPREVOUT enables signatures that don't bind to a specific input UTXO, which is useful for eltoo-style payment channels.

  2. What is a 'spinoff' or 'airdrop fork' and how does it differ from a traditional contentious hard fork?

    Answer: A spinoff gives holders of existing Bitcoin a new coin at a snapshot block without intending to replace Bitcoin or compete for the same chain

    Spinoffs like Bitcoin Gold create a new independent coin distributed to BTC holders at a snapshot, without the combative 'this IS Bitcoin' framing of BCH.

  3. In BIP 9 signaling, what happens if a soft fork proposal does not reach the activation threshold before its timeout date?

    Answer: The proposal fails and must be re-proposed under a new BIP with a new timeout window

    A BIP 9 deployment that times out transitions to 'FAILED' state, requiring a new deployment proposal if developers wish to pursue the change again.

  4. How did the activation of Taproot in November 2021 differ from the contentious SegWit activation in 2017?

    Answer: Taproot achieved overwhelming miner consensus quickly and had no significant community opposition, unlike SegWit's contentious political battle

    Taproot signaled above 90% almost immediately with minimal opposition, contrasting sharply with the years-long SegWit debate.

  5. What is 'hash war' and which 2018 Bitcoin fork event is most associated with this term?

    Answer: A period where BCH and BSV miners directed massive hash rate at each other's chains to achieve the longest chain after their November 2018 split

    The BCH/BSV split in November 2018 triggered a 'hash war' where both factions rented massive hash power to out-mine the opposing chain.

  6. Why is soft fork backward compatibility described as 'one-way'?

    Answer: Old (non-upgraded) nodes still accept new-rule blocks as valid, but upgraded nodes reject old-rule blocks

    Old nodes see new-rule blocks as valid (tighter rules are a subset of old rules), but upgraded nodes reject any block that violates the new rules, making compatibility asymmetric.

  7. What is the primary criticism of 'miner-activated' upgrade mechanisms from a decentralization standpoint?

    Answer: They give a small group of mining pool operators disproportionate veto power over protocol changes that affect all Bitcoin users

    Critics argue MASF concentrates upgrade authority in a few large pools, undermining the broader network of users and full node operators who have no formal vote.