
Why Scaling Bitcoin with Sharding Is Very Hard (2015) - elmar
https://petertodd.org/2015/why-scaling-bitcoin-with-sharding-is-very-hard
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davidgerard
this is pretty good. Key line for me:

> How do you prove that a coin has validly been spent? First, prove that it
> hasn’t already been spent! How do you do that if you don’t have the
> blockchain data? You can’t, and no amount of fancy math can change that.

and also, something Bitcoin devs realise that Bitcoin fans often don't seem
to:

> On the other hand, decentralization isn’t cheap: using PayPal is one or two
> orders of magnitude simpler than the Bitcoin protocol.

~~~
janitor61
Why couldn't you use a sufficiently large bloom filter to determine if a coin
has been spent?

~~~
thinkloop
How do you verify the authenticity of the bloom filter?

~~~
teddyh
That’s not really a problem – anyone could verify it by downloading the full
blockchain. The important thing is that you don’t need the full blockchain to
get a negative answer from a bloom filter, which helps.

The problem happens when you get a _positive_ answer from the bloom filter;
i.e. a coin _might_ have been previously spent. As far as I know you then
_still_ need the full blockchain to verify.

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wyldfire
Some coins do sharding by not using a blockchain at all. e.g. RaiBlocks [1]
uses a "block-lattice" approach. It is a Proof-of-stake-secured coin.

[1]
[https://raiblocks.net/media/RaiBlocks_Whitepaper.pdf](https://raiblocks.net/media/RaiBlocks_Whitepaper.pdf)

~~~
nerdponx
There's also the Iota "Tangle":
[https://iota.org/IOTA_Whitepaper.pdf](https://iota.org/IOTA_Whitepaper.pdf)

~~~
xorcist
Sharding isn't any easier with the Tangle.

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DennisP
It's hard but not necessarily impossible. Here's Ethereum's sharding FAQ:

[https://github.com/ethereum/wiki/wiki/Sharding-
FAQ](https://github.com/ethereum/wiki/wiki/Sharding-FAQ)

~~~
vmialik
Hi Dennis, a friend recommended you to me for Ethereum smart contract audit,
are you open/available for a project?

~~~
DennisP
Willing to talk at least, how do I contact you?

------
wslh
SPECTRE: [https://medium.com/@avivzohar/the-spectre-
protocol-7dbbebb70...](https://medium.com/@avivzohar/the-spectre-
protocol-7dbbebb707b5)

~~~
tfha
That is not a sharded blockchain and shares the same fundamental restriction:
all nodes must verify all blocks.

(though it does offer some nice improvements, we're taking factors of 2-5, not
100-1000)

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epx
Bitcoin is over.

~~~
quickthrower2
... $15,000

