Abstract Assessment 3

1.Nodes use __________ i) used to enforce network rules. A node who publishes blocks that violate the rules waste the_____ ii) used to generate the valid proof of work.

i) consensus, ii) hashpower

i) nonces, ii) nonce

i) code, ii) hash

i) hashpower, ii) energy investment

2.One of the ways it is possible to attack the integrity of the ledger is for a node operator to include in a block a transaction that _________ i) coins that were previously spent; or to otherwise include a transaction in a block that is invalid per network rules. As long as that node is not supported by more than half of the _________ ii) , they will not be able to propagate and build upon blocks containing invalid transactions.

i) returns, ii) nodes

i) double spends, ii) network hashpower

i) double spends, ii) nodes

i) returns, ii) network hashpower

3.A ________ is a fraudulent transaction in which a user sends coins they have already spent, back to themselves.

Poisoned transaction

Reverse spend

Double spend

Unspendable transaction

4.As transaction __________ i) grows commensurate with network usage, individual node operators will invest in __________ ii) that increases their capacity to validate all available transactions and gain access to a larger pool of fee revenue.

i) value ii) more nodes

i) number ii) hash power

i) fee revenue ii) infrastructure

i) value, ii) hash power

5.Nodes will accept the ______________ i) version of a transaction as the valid version of that transaction, and consider any subsequent transactions that try to spend the same inputs as an attempt at ________ ii)

i) last, ii) fraud

i) latest, ii) a 51% attack

i) highest fee, ii) deception

i) first seen, ii) double spending

6.What proof do new miners or returning miners have that the chain they are mining is the valid one?

The chain with the most hashpower is valid.

The chain with the most transactions in it is valid.

The longest chain that is compliant to the network rules is valid.

The node must wait for a valid message to be broadcasted over the network.

7.What do block announcements provide nodes and what happens if two blocks are discovered simultaneously?

Using block announcements, nodes are provided the option to build upon the designated proof-of-work chain and will begin building a block upon it. Occasionally, blocks are discovered simultaneously, leading to one of those blocks being orphaned.

Using block announcements, nodes accept the first valid block which builds upon the longest proof-of-work chain as the next block in the chain, and will begin building their block upon it. Occasionally, two blocks are discovered simultaneously, leading to one of those blocks being orphaned.

Using block announcements, nodes accept any block as the next block in the chain, and will begin building their block upon it. Occasionally, blocks are discovered simultaneously, leading to one of those blocks being called an uncle.

Using block announcements, nodes are told which block is valid and where to build the next block in the chain. Occasionally, blocks are discovered simultaneously, leading to the smaller of those blocks being deleted.