B3. Bitcoin blocks

All Bitcoin block headers have the same size

• True

• False

All Bitcoin blocks have the same size.

• True

• False

Block headers contain:

• a pointer to the next block header

• a list of transaction hashes

• the merkle root of the transactions in the block

• the signature of the miner

Block timestamps...

• specify the exact time when the block was mined

• are always increasing with each new block

• are not validated

• are used to adjust difficulty

Given a Merkle Tree with 8 transactions, in order to proof that Tx8 is in the block, we need to show:

• Tx8, h8, h78, h5678

• Tx8, h7, h56, h1234

• Tx8, h6, h34, h1234

• Tx8, h2, h12, h5678

A transaction is invalid if...

• it spends outputs that have not been already spend

• it is a coinbase transaction

• it spends an ouput that has already been spend

• the sum of input amounts is different than the sum of output amounts

A block is invalid if...

• it contains no transactions

• it contains at least one transaction

• the block hash is lower than the target

• the merkle root is correct

The chain with the most number of blocks is always the one that contains the most work

• True

• False

Difficulty is...

• adjusted to account for the number of transactions in the network

• adjusted every 2 weeks

• adjusted every 2016 blocks

• always increasing

If 2016 blocks are mined in a single day, what happens with difficulty?

• it will be decreased

• it will be increased

• it will not change

• it won't be adjusted until 2 weeks has passed