I have a PDF presentation to go with this draft:
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What is a blockchain?
A blockchain is...
[snippets of text pop up as the words are uttered]
...a shared public ledger that consists of a sequential record of all transactions, usually in a cryptocurrency system, that records ownership both present and at all points in the past of all units that circulate within that system, in order to mitigate double-spending, which is a core design challenge of distributed, untrusted peer-to-peer protocols, the integrity and the chronological order of which are enforced with military-grade cryptography buzzwords and techno-gobbledygook, hand-waving, and ooohhh...
[Gold Bitcoin disks appear, onee-at-a-time to fill the scree. A 'ka-chink' sound accompanies each new coin image, and they appear slowly at first and faster through the dozen or so events.]
Let's try that again.
A blockchain is...
...a shared ledger.
[red arrow pops up]
[first spreadsheet image]
Imagine a spreadsheet with 1.15 x 10^77 columns. To put that into perspective, according to WolframAlpha, the earth is made of approximately 1 x 10^50 atoms meaning that the number of columns is about 3.7 x 10^28 earths' worth of atoms.
Remember, one million is 10^6, and a trillion is 10^12. So, 1.15 x 10^77 is... a LOT.
Each of these columns is like an account that someone controls, and it records how many units--'coins', 'shares', or whatever--one owns...
...and the total amount is known at any moment.
This unimaginably wide spreadsheet records every transfer of numbers from one column to another column...
Each row of the spreadsheet is like a sheet of paper, on which all of the transactions completed within some average amount of time are batched up and confirmed in what we call a 'block' of transactions. And, as the number of rows grows, the spreadsheet becomes like a stack of sheets of paper that we call a 'blockchain'.
And, instead of having an individual's name at the head of each column--because coming up with 1.15 x 10^77 unique names would be waaayyy too hard, each column is identified with a unique string of random characters...
How do we know that a copy of the transaction history--the blockchain--is correct? Well...
[copies of spreadsheet pop up around the world]
...because ANYone, ANYwhere in the world can have a copy of it, and if a copy does not match everyone else's, it gets ignored. As long as 50%
of those confirming transactions agree one a particular copy of the blockchain, that one *IS* the correct version.
Because everyone is looking over everyone else's shoulder, no one needs to TRUST anyone else, and if anyone fiddles with the numbers in his or her copy of the blockchain, everyone else will know it and ignore that copy.
[red arcs bounce around the globe]
And *THIS* enables us to transfer numbers from one column to another column, no matter... where... in... the world... the parties are... who... control a given column in this immensely wide transaction record.
[hold on final image with multiple red arcs]
...as if national boundaries that keep people apart did not even exist.
How do you secure
Today, there are two general categories of solutions:
Proof of Work and Proof of Stake.
First, with Proof of Work transaction processors confirm the validity of the most recent transactions; whereas with Proof of Stake transaction processors confirm the validity of the most recent transactions.
Next, with Proof of Work the transaction processors record that block of transactions on a page; whereas with Proof of Stake the transaction processors record that block of transactions on a page.
Then, with Proof of Work the transaction processors keep buying lottery tickets that until one eventually buys a winning ticket which is expensive, very tedious, and wasteful; whereas with Proof of Stake the transaction processors take a vote among the holders of the units in the system, like a one-vote-per-share election in a company.
Finally, with both Proof of Work and Proof of Stake the transaction processors add the new page to the stack of all previous transactions and start a new block.
After all that is done, the winning Proof of Work transaction processor collects a prize of some arbitrarily predetermined units for having been the lucky lottery winner; whereas the Proof of Stake transaction processor whose turn it was to confirm the current block receives a share of the transaction fees generated by that block of transactions.
The major difference between Proof of Work and Proof of Stake, is that Proof of Work vests the voting power in the hands of the transaction processors, who might not even hold any units--'coins', 'shares', or whatever one calls them--in the system
; whereas Proof of Stake works like conventional corporate governance, in which each unit-holder gets to vote in proportion to his or her stake in the system.
To learn more...