What is sharding? How this will overcome the scalability issues of blockchains?

[Jace Lee]

I was reading an article and came across the word "Sharding". It is nothing but a form of database partitioning, also known as horizontal partitioning. The idea of sharding is to move from a linear execution model(like in Ethereum) and allow multiple, parallel transactions processing at the same time. This can improve the scalability issues and can increase the number of transactions per second(TPS).

Some blockchains already using sharding are Zilliqa, the first public blockchain to implement sharding. It was able to achieve 2,828 TPS in its testnet. The Ethereum foundation is also planning to introduce sharding as a part of Ethereum 2.0.

If the sharding can increase the speed of the transaction validations and therefore increases the speed of the entire network, then why all cryptocurrencies don't implement this on the blockchain to reduce the scalability issues?

Are there any drawbacks in Sharding? Are there any alternative solutions to sharding? Please share your thoughts on this.


Source: https://cointelegraph.com/explained/sharding-explained

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[pooya87]

the main problem with sharding is keeping it decentralized. sharding can work with a database easily but blockchain is not a normal database. the current design of a decentralized trustless cryptocurrency is that you literary start from ground zero and download every single transaction that has ever been made and verify them one by one then add to your database. finally you will be left with a blockchain (database) that is cryptographically secured and verified so you can trust it. if you introduce sharding you are removing that trustlessness and would require trusting others.

so far there has been some proposals like BFT sharding, Zilliqa, Merklix tree,... and they all try to address these issues but none of them have ever come close to solving them.
on top of that it introduces new attack surface to malicious attackers that never existed before. for example when you use what is called "validators" an attacker can easily take over majority of them that are responsible for validating a particular block and can successfully submit an invalid block to the chain. this take over can be either by actually taking over the validators or simply bribing them to do his dirty work.

this will also kill SPV clients since they will no longer have any way of protecting themselves against fraud.

[bitmover]

This forum is certainly one of the best place to learn about blockchain.

So many people come here talking about all those new technologies which are supposedly better than bitcoin.
I hear that everywhere, even in my real life when people ask me about bitcoin "But isn't bitcoin using an old tech? slow and expensive. A better crypto may show up".

This idea is all over the media, and it is not entirely true. Decentralization and security are the main pillars of bitcoin, and trading them for scalability will only weaken bitcoin. And scalability is not an issue yet, as most of the time transactions are cheap and somehow fast (i am satisfied with 3-4sat/byte and about 2hours, which I get most of the time).

[Jace Lee]

the main problem with sharding is keeping it decentralized. sharding can work with a database easily but blockchain is not a normal database. the current design of a decentralized trustless cryptocurrency is that you literary start from ground zero and download every single transaction that has ever been made and verify them one by one then add to your database. finally you will be left with a blockchain (database) that is cryptographically secured and verified so you can trust it. if you introduce sharding you are removing that trustlessness and would require trusting others.

Thanks for your thoughts on this. Don't you think the process of downloading every transaction and verifying them one by one is a tedious and long process. This requires a lot of time. Instead in sharding, the blockchain will divide into seperate shards. Nodes will have to validate the transactions that are assigned to that node only instead of whole ledger.

And for security risks, Ethereum has proposed a random sampling concept where authorized person will verify the block authentication. This can eliminate the trustlessness. What do you say?

[pooya87]

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Thanks for your thoughts on this. Don't you think the process of downloading every transaction and verifying them one by one is a tedious and long process. This requires a lot of time. Instead in sharding, the blockchain will divide into seperate shards. Nodes will have to validate the transactions that are assigned to that node only instead of whole ledger.

of course it is time consuming but having a decentralized and secure money doesn't come free so it is acceptable. the alternative (sharding in this case) has to be able to give us the same exact security and decentralization level for it to be considered. but shading comes at a cost too, and that cost is lower security and less decentralization.

And for security risks, Ethereum has proposed a random sampling concept where authorized person will verify the block authentication. This can eliminate the trustlessness. What do you say?

that is called the "validator" that i mentioned above and as i said it opens up new attack surface.

[joniboini]

And for security risks, Ethereum has proposed a random sampling concept where authorized person will verify the block authentication. This can eliminate the trustlessness. What do you say?

Random validator might be able to give some degree of security but it won't give you the same security as a full node does.

I believe that's not the best solution if you want a blockchain for a decentralized currency. But for stuff like a smart contract or custom blockchain, it might be an alternative especially if the validators are known beforehand.

[Jace Lee]

That means you need to trust the authorized person

I didn't mean that we need to trust an authorized person completely. If he has given an authority to verify the block, then he will be responsible for everything that happens to the blocks that is assigned to him.