CBP Forks and Network Upgrades 3 — Questions and Answers
Question 1: What is the primary purpose of replay protection in a hard fork event?
- To prevent miners from switching between chains
- To ensure transactions on one chain cannot be rebroadcast and confirmed on the other chain (Correct answer)
- To speed up block confirmation times on the new chain
- To prevent double-spending within a single blockchain
Correct answer: To ensure transactions on one chain cannot be rebroadcast and confirmed on the other chain
Replay protection modifies transaction signing so a valid transaction on one fork is invalid on the other, protecting users from unintended fund movement.
Question 2: Bitcoin Cash implemented which mechanism to adjust mining difficulty more rapidly after its fork from Bitcoin?
- The same 2016-block difficulty adjustment as Bitcoin
- An Emergency Difficulty Adjustment (EDA) to cope with fluctuating hash rate (Correct answer)
- A fixed difficulty that never changes
- A user-vote system to set difficulty every 100 blocks
Correct answer: An Emergency Difficulty Adjustment (EDA) to cope with fluctuating hash rate
BCH introduced an Emergency Difficulty Adjustment that could lower difficulty significantly if blocks were too slow, addressing hash rate instability post-fork.
Question 3: When analyzing a proposed hard fork, which factor most directly determines whether two chains will survive long-term?
- The programming language used to implement the change
- Whether each chain has sufficient economic activity and hash rate to sustain itself (Correct answer)
- The number of BIPs referenced in the proposal
- Whether the fork was announced more than one year in advance
Correct answer: Whether each chain has sufficient economic activity and hash rate to sustain itself
Long-term chain survival depends on sustained economic value attracting miners and users; without both, a chain collapses.
Question 4: What does 'flag day' activation mean in the context of Bitcoin forks?
- Miners signal readiness by setting a specific flag in the coinbase transaction
- A pre-specified block height or date after which nodes enforce new rules unconditionally (Correct answer)
- A community vote held annually to approve protocol changes
- A special genesis block that initializes the new fork chain
Correct answer: A pre-specified block height or date after which nodes enforce new rules unconditionally
Flag day activation means new rules take effect at a predetermined point regardless of miner signaling percentage.
Question 5: Which scenario describes an 'accidental hard fork'?
- Developers intentionally release incompatible software to create a new coin
- A software bug causes some nodes to accept blocks that others reject, temporarily splitting the chain (Correct answer)
- Miners vote to change the consensus rules without developer approval
- Users deliberately run old software to resist an upgrade
Correct answer: A software bug causes some nodes to accept blocks that others reject, temporarily splitting the chain
The March 2013 Bitcoin incident is a classic example where a BerkeleyDB lock limit bug caused a temporary chain split between v0.7 and v0.8 nodes.
Question 6: In the context of SegWit2x (2017), why did the hard fork portion ultimately fail to activate?
- The code contained a critical security vulnerability discovered at the last minute
- Key signatories withdrew support and the fork lacked sufficient node and economic backing (Correct answer)
- The US government issued a ruling preventing its activation
- Miners refused to signal because the block reward would have been halved
Correct answer: Key signatories withdrew support and the fork lacked sufficient node and economic backing
Major SegWit2x backers publicly withdrew weeks before the planned November 2017 activation, collapsing support for the 2MB block hard fork.
Question 7: What is 'wipe-out risk' in the context of a soft fork?
- The risk that miners will erase transaction history during a soft fork
- The risk that a minority miner chain is completely orphaned by the majority chain enforcing new rules (Correct answer)
- The chance that wallet software deletes user keys after the upgrade
- The possibility that all pre-fork UTXOs become unspendable
Correct answer: The risk that a minority miner chain is completely orphaned by the majority chain enforcing new rules
In a soft fork, old-rule blocks produced by non-upgraded miners are invalid to upgraded nodes and will be orphaned, 'wiping out' that chain.
CBP Forks and Network Upgrades 3
What is the primary purpose of replay protection in a hard fork event?