CBP Forks and Network Upgrades 2 — Questions and Answers
Question 1: What distinguishes a User-Activated Soft Fork (UASF) from a Miner-Activated Soft Fork (MASF)?
- UASF requires 95% miner signaling while MASF requires only 51%
- UASF is enforced by full nodes regardless of miner support, while MASF relies on miners to signal readiness (Correct answer)
- UASF creates a new coin while MASF keeps the existing chain
- UASF only applies to transaction rules while MASF applies to block rules
Correct answer: UASF is enforced by full nodes regardless of miner support, while MASF relies on miners to signal readiness
A UASF activates based on full node enforcement on a specific date, bypassing the need for miner majority support.
Question 2: During the 2017 Bitcoin scaling debate, BIP 148 was a proposal for which type of activation?
- A hard fork to increase block size to 2MB
- A UASF to force SegWit activation by August 1, 2017 (Correct answer)
- A miner-activated soft fork for SegWit2x
- A soft fork to reduce the block time to 5 minutes
Correct answer: A UASF to force SegWit activation by August 1, 2017
BIP 148 specified that nodes would reject blocks not signaling SegWit support starting August 1, 2017, making it a UASF.
Question 3: What is a 'velvet fork' in the context of Bitcoin protocol upgrades?
- A fork that requires all nodes to upgrade simultaneously
- An upgrade that is backward compatible and does not split the chain even if not all nodes upgrade (Correct answer)
- A type of hard fork that preserves both chains permanently
- A miner-initiated fork that temporarily splits the network
Correct answer: An upgrade that is backward compatible and does not split the chain even if not all nodes upgrade
A velvet fork is a protocol upgrade designed so that non-upgraded nodes can still participate without being excluded from the network.
Question 4: What happened to the Bitcoin XT fork proposal in 2015?
- It successfully activated and became the dominant Bitcoin chain
- It was abandoned after failing to gain sufficient node and miner adoption (Correct answer)
- It merged back into Bitcoin Core after six months
- It became Bitcoin Cash after a replay attack
Correct answer: It was abandoned after failing to gain sufficient node and miner adoption
Bitcoin XT proposed 8MB blocks but failed to achieve the 75% miner threshold needed for activation, leading to its abandonment.
Question 5: In a soft fork, which group's behavior change is strictly required to enforce the new rules?
- All end users must update their wallets
- A majority of miners must enforce the new stricter rules (Correct answer)
- All light clients must update their SPV software
- Only developers need to release updated code
Correct answer: A majority of miners must enforce the new stricter rules
In a soft fork, miners enforcing the new stricter rules ensure that non-compliant blocks are orphaned, making old nodes still accept the valid chain.
Question 6: What is 'chain death spiral' risk associated with hard forks?
- A scenario where high transaction fees cause users to abandon the chain
- A minority chain losing so much hash rate that block times become excessively long, making it unusable (Correct answer)
- When a fork causes a replay attack that empties all wallets
- When developer disagreements prevent any future protocol upgrades
Correct answer: A minority chain losing so much hash rate that block times become excessively long, making it unusable
If a minority chain retains very little hash power after a fork, difficulty adjusts slowly and blocks may take hours or days, potentially killing the chain.
Question 7: Which Bitcoin Improvement Proposal introduced the concept of version bits to coordinate multiple soft fork activations simultaneously?
- BIP 9 (Correct answer)
- BIP 16
- BIP 91
- BIP 141
Correct answer: BIP 9
BIP 9 introduced version bits signaling, allowing miners to signal readiness for up to 29 soft forks concurrently using bits in the block version field.
CBP Forks and Network Upgrades 2
What distinguishes a User-Activated Soft Fork (UASF) from a Miner-Activated Soft Fork (MASF)?