Assessment 2

4 out of 6

1. Each node typically broadcasts _____ transactions to all other nodes, even _____.

   1. valid, if they do not plan to place them in a block. ✓

   2. nvalid, they won’t be included in a block.

   3. low fee, though some low fee transactions may be retained for a block if there aren't enough high fee transactions.

   4. complex, with large fees as it's faster to process simple transactions.

2. What does the First Seen Rule protect against?

   1. Nodes withholding transactions from the rest of the network.

   2. Double spends by users. ✓

   3. Double spends by nodes.

   4. All of the above.

3. What can the network do to a double spending node?

   1. Nothing.

   2. It can reject its blocks. ✓

   3. It can fork it off onto a separate chain.

   4. It can shut down the node.

4. What must occur each time one or more transactions are added to the Merkle tree?

   1. Each transaction’s TXID must be re-calculated.

   2. The Merkle root must be re-calculated. ✓

   3. They must be removed from the mempool.

   4. The parent transactions must be pruneable.

5. The linked block headers combined form a structure known as what?

   1. The longest chain of proof-of-work.

   2. The ledger.

   3. A Directed Acyclic Graph. ✓

   4. A working blockchain.

6. How is a nonce used to generate proof-of-work?

   1. By finding a nonce that once incorporated into the hash puzzle, the subsequent value must equal the difficulty target to be considered successful.

   2. By cycling hash puzzles against the nonce until a hash puzzle is unlocked that meets the difficulty target of the network.

   3. By passing single use values through the nonce field modulating the block header to form an output value less than or equal to the difficulty target. ✓

   4. By searching for a nonce that when combined with the hash puzzle forms a number that matches the difficulty criteria.