
Blockchains explained visually (part 1 of 2) - unwttng
https://unwttng.com/what-is-a-blockchain
======
Freak_NL
> Toggle pointless gifs off

First time I've seen that. That should really be the standard for any author
who decides to pepper their articles with 'memes' and other unrelated
distractions.

Perhaps this is a cultural or generational thing that I am interpreting in the
wrong way, but whenever I follow a link to a blog post filled with these kinds
of distracting animated pictures I tend to just give up on the article after
encountering the first one. I just can't fathom why someone who wishes to
inform or enlighten readers on a certain topic feels the need to include a
plethora of irrelevant distractions.

Nice to have a way to turn them off so I can give the article a chance based
on its merits rather than the presence of memes.

~~~
Moru
There was a lot of complaints a few weeks ago on an article with animated
gifs. That person changed the homepage with a toggle, mabe it's the same
person?

~~~
unwttng
It's the same person! That person is me.

~~~
avip
We want the shitcoin.com domain!

~~~
abrkn
That's me. Maybe I'll do a no GIF version for my next review.

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ahussain
The best explanation of blockchain has to be (unsurprisingly) 3Blue1Brown:
[https://www.youtube.com/watch?v=bBC-
nXj3Ng4](https://www.youtube.com/watch?v=bBC-nXj3Ng4)

Would highly recommend watching this video for anyone who hasn't already.

~~~
andreasklinger
My favorite:
[https://www.youtube.com/watch?v=_160oMzblY8](https://www.youtube.com/watch?v=_160oMzblY8)

It explains from ground up without getting complicated - it basically
demystifies the whole thing completely

i give this to everyone - even to non technical people

~~~
dvt
I've seen this before and it's so awesome. Best block chain explanation I've
ever come across (much better than 3blue1brown imo).

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IgorPartola
This part of the blockchain always made perfect sense to me. The magic is in
the proof of work and proof of stale stuff as well as smart contracts.

~~~
unwttng
I think the logical split I've made between those two areas is a good one
since people tend to be in one of two camps in terms of how comfortable they
are with all this. Hopefully I can do justice to the second part.

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monokh
> See how the hash-chaining mechanism of a blockchain means that even a single
> corrupt or tampered-with block will invalidate the entire chain after it.

Is that strictly required to understand that the entire chain is invalidated?
Since blocks are in order, if block X's previous hash doesn't check out, can't
we just assume that every block thereafter is also invalid? Effectively a fork
has happened at X-1 block.

I'm guessing there are more dynamics (speed?) that come into this. Maybe the
following questions will make it more clear:

1\. How do the blocks update when there is a change in a past block?

2\. In the real world, what process does a node use to validate the chain on
an ongoing basis?

~~~
Buttes
Someone can mine and broadcast blocks that reference an old block, nodes will
store the block, in case more are published and it becomes the longest chain,
but will otherwise ignore it.

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k__
I always read that crypto currencies will replace money, because they are
distributed.

But does a blockchain, that is at the core of every(?) crypto currency really
scale well?

Keeping the whole ledger constantly available seems rather storage and traffic
intensive to me.

~~~
davidgerard
tl;dr no. Bitcoin has a theoretical limit of 7 transactions/sec (or
4200/10min) for everyone in the world. Ethereum can do up to about 14-16
tx/sec.

There are plans to fix this - sharding on Ethereum, Lightning Network on
Bitcoin - but both are largely vaporware at this stage.

In practice, a lot of the transaction action happens inside the individual
exchanges, not on the blockchain itself - so we already have a "level 1" and
"level 2" system.

Also, there's issues of securing your bitcoins - "be your own bank" means "be
your own extremely knowledgeable chief security officer". This is why even a
lot of big holders keep a lot of money on exchanges (and lost lots in Mt.
Gox). And why losses due to human error are extremely common.

The blockchain is more interesting than useful.

~~~
JudasSicarius
"In practice, a lot of the transaction action happens inside the individual
exchanges, not on the blockchain itself - so we already have a "level 1" and
"level 2" system."

Can you expand on this a bit? Is it somewhat analogous to the role that dark
pools play in the stock market?

~~~
davidgerard
By quantity a hell of a lot more individual trades happen on the exchanges
than on chain. It's not hidden - just not as radically transparent as on-chain
transactions. But obviously harder to gather data on, has none of the
blockchain's cryptographic guarantees, etc. It turns out the actual traders
care more about getting a good price than the ideological basis for the
blockchain. And that's even in a situation where you can't really trust the
exchanges - rife with insider trading, wash trades, front running, spoofing,
whether a Tether can be counted as a dollar, etc., things that are highly
illegal in normal security trading. As long as the number keeps going up,
everyone seems okay with this.

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seanalltogether
One thing that never clicked with me before is that the blockchain is really
just a historical ledger, its not actually referenced in real time. When you
send a transaction out on the network, nobody is actually validating it
against the blockchain. Instead every node is expected to process the
blockchain to produce a realtime database called the UXTO which provides a
fast lookup to tell you if coins can be spent or not. So the blockchain is a
history or transactions, while the UXTO is a statement of all current
balances.

So while the BTC blockchain is 137 GB in size, the UXTO is only 2.7 GB which
easily fits in memory.

~~~
Buttes
And you really only need to track UXTO for your own address if you're not a
full node, and that will be very small.

------
zeep
> hexadecimal notation (that is, using 0-9 and a-z)

should be hexadecimal notation (that is, using 0-9 and a-f)

~~~
doodpants
That jumped out at me too. At first I thought, "does the author not understand
how hexadecimal works, or is this merely a case of sloppiness or imprecision
in his description?" Then I got to the part that said:

> There shouldn't be loads of them that start with an "A", or loads that end
> with ten "X"s, or anything like that.

This leads me to further doubt about the author's grasp of hexadecimal.

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chrisaycock
_IEEE Spectrum_ has a special report about blockchains:

[https://spectrum.ieee.org/static/special-report-
blockchain-w...](https://spectrum.ieee.org/static/special-report-blockchain-
world)

It goes into permissioned ledgers and smart contracts, among other
applications.

------
Cognitron
Something I noticed, but didn't see in the article (unless I just missed it).
In reference to the security part at the end, if the hash only included the
previous block's data, and not its previous hash. If you could edit two
consecutive blocks you could change, say, block 2's data and block 3's
previous hash. Now everything looks fine because this doesn't change block 3's
data so block 4's previous hash looks fine and everything looks legit. Seems
like a greater concern than breaking the chain because it wouldn't be detected
unless you compared two versions of the chain.

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tristan_ph
this is still my favorite
[https://anders.com/blockchain/](https://anders.com/blockchain/)

~~~
segmondy
yup, I was able to implement a basic blockchain at once the moment I watched
that demo.

------
baby
Skip this article (which hilariously tries to rename and redefine a hash
properties) and play with this instead:
[https://anders.com/blockchain/](https://anders.com/blockchain/)

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sAbakumoff
I just would like to say thanks to the author for spending his time on this
article. I found it very well written and I look forward to seeing part 2. I
recommend this article to everyone who asks me about the blockchain
technology.

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gtrubetskoy
Nice.

You should probably mention that what you are describing is a variant of a
Merkle tree.

[https://en.wikipedia.org/wiki/Merkle_tree](https://en.wikipedia.org/wiki/Merkle_tree)

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cslarson
FYI, in the first paragraph you misspelled Ethereum as "Etherium".

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t0mislav
Nice and eloquent! Will read also other articles.

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caylorme
"it's quite customary to represent hashes in hexadecimal notation (that is,
using 0-9 and a-z) - that's what we'll use in this article." \-- hexadecimal
is 0-9 and a-f

