Blockchain Revolution

participate. Proof of activity is another mechanism; it combines proof of work and
proof of stake, where a random number of miners must sign off on the block using a
cryptokey before the block becomes official.
9
Proof of capacity requires miners to
allot a sizable volume of their hard drive to mining. A similar concept, proof of
storage, requires miners to allocate and share disk space in a distributed cloud.
Storage does matter. Data on blockchains are different from data on the Internet in
one important way. On the Internet, most of the information is malleable and fleeting,
and the exact date and time of its publication isn’t critical to past or future
information. On the blockchain, bitcoin movement across the network is permanently
stamped, from the moment of its coinage. For a bitcoin to be valid, it must reference

---

its own history as well as the history of the blockchain. Therefore, the blockchain
must be preserved in its entirety.
So important are the processes of mining—assembling a block of transactions,
spending some resource, solving the problem, reaching consensus, maintaining a copy
of the full ledger—that some have called the bitcoin blockchain a public utility like
the Internet, a utility that requires public support. Paul Brody of Ernst & Young thinks
that all our appliances should donate their processing power to the upkeep of a
blockchain: “Your lawnmower or dishwasher is going to come with a CPU that is
probably a thousand times more powerful than it actually needs, and so why not have
it mine? Not for the purpose of making you money, but to maintain your share of the
blockchain,”
10
he said. Regardless of the consensus mechanism, the blockchain
ensures integrity through clever code rather than through human beings who choose to
do the right thing.