Assessment 4

ASIC mining machines ____ values through a supplied ____ and with each value the block header is hashed twice using SHA256. A block header is valid if the double hash is ______ and can be added to the chain.

• adds, block header, more difficult than the difficulty target.

• test, hash function, equal to or less than the difficulty target.

• hash, block, greater than the difficulty target.

• increment nonce, block header, less than the difficulty target.

What do pool-miners use their mining candidate for?

• To generate unique block headers and coinbase transactions which they provide to their ASICs.

• Incrementally iterating a nonce as an input to the candidate header before hashing with the ASIC miners.

• For their ASICs to perform 4.3 billion nonce cycles on, in order to generate proof-of-work.

• All of the above.

How does a node signal consensus?

• By propagating a first seen block to the rest of the network.

• By sending a first seen block to a pool-miner in order to be hashed into the next block it is forming.

• By forming a block template using the new block’s hash for the prevHash field.

• By retaining a first seen block’s block header for its record.

What happens when two valid blocks are found with the same previous block hash?

• The First Seen Rule applies.

• An Orphan Race.

• The node who found them first choses by incorporating one of the block’s hash into their next block.

• Both blocks are orphaned.

Since nodes can freely accept and reject blocks, it is important that they are aware of what the ______ the network accepts as the valid chain in order to be sure they are always building on the ______ of blocks and not producing ____ blocks.

• most recent block, valid chain, orphan.

• majority of nodes on, longest valid chain, invalid.

• different groups of nodes on, most recent, on orphaned.

• most connected nodes on, most recent chain, on invalid.