<blockquote>
  <p>...you can download only the files that you need, and no need to download everything with it.</p>
</blockquote>

<p>To do this, you would need to trust that you are receiving the correct files (blocks) from your peers. If they lie to you and serve a false history, how will you know?</p>

<p>A full node downloads the blockchain so that it can independently validate the current state of the network, starting from the genesis block. By working through the network's history, the full node can verify for itself what the current state of the network is, without needing to trust any peers to not lie. </p>

<p>A lightwallet can download just the block headers (80 bytes per block) and use them to help verify that the wallet's transactions are authentic Bitcoin transactions. </p>

<p>But in both cases the node/wallet must have a full history of blocks/headers in order to not be trivially taken advantage of. So I think that an application which only downloads parts of the blockchain history is likely of little use, due to the potential for abuse of trust. </p>

CC BY-SA 4.0
2019-08-27T08:20:15.160Z
I'm aware that a node might lie, and also aware of the light node concept. But, just like downloading a torrent file, you download it from different random users, therefor, if one node tried to give you a fake block, other nodes will also have to give you the exact fake block. which a very unlikely situation to happen, right?
l Wawa
CC BY-SA 4.0
2019-08-27T08:28:06.437Z
*“Unlikely to happen”* generally isn’t the sort of security guarantee I’d want for my money. Why open yourself up to targeted attacks?
chytrik
CC BY-SA 4.0
2019-08-28T02:49:56.197Z
Really? because this is the model that blockchain uses as a security mechanism. An example of that is 51% attack, although it's a possibility, but it's unlikely to happen.
l Wawa
CC BY-SA 4.0
2019-08-28T04:27:26.237Z
A 51% attack has a huge monetary cost, whereas an eclipse attack does not. So these two attacks are not analogous in this way; a 51% attack is **EXTREMELY** more unlikely.
chytrik
CC BY-SA 4.0
2019-08-27T08:05:29.927Z
2019-08-27T08:05:29.927Z
chytrik
<p>Is it possible to make a blockchain system that allows you to download specific blocks from the blockchain instead of the whole blockchain?</p>

<p>In my case for example, I only need 1 giga of the whole chain, so why do I have to download all the blocks? I understand that this is done to make sure that the chain doesn't get tampered with and so on...</p>

<p>But is it possible to make it like a torrent file? where you can download only the files that you need, and no need to download everything with it.</p>

<blockchain>
can we make a blockchain that works like torrent?
l Wawa
# can we make a blockchain that works like torrent?

(Asked by: username_0 on 2019-08-27)

Is it possible to make a blockchain system that allows you to download specific blocks from the blockchain instead of the whole blockchain?

In my case for example, I only need 1 giga of the whole chain, so why do I have to download all the blocks? I understand that this is done to make sure that the chain doesn't get tampered with and so on...

But is it possible to make it like a torrent file? where you can download only the files that you need, and no need to download everything with it.

**Tags:** blockchain


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## 1 answers

### Answer by username_1 on 2019-08-27. Score: 1

> ...you can download only the files that you need, and no need to download everything with it.

To do this, you would need to trust that you are receiving the correct files (blocks) from your peers. If they lie to you and serve a false history, how will you know?

A full node downloads the blockchain so that it can independently validate the current state of the network, starting from the genesis block. By working through the network's history, the full node can verify for itself what the current state of the network is, without needing to trust any peers to not lie.

A lightwallet can download just the block headers (80 bytes per block) and use them to help verify that the wallet's transactions are authentic Bitcoin transactions.

But in both cases the node/wallet must have a full history of blocks/headers in order to not be trivially taken advantage of. So I think that an application which only downloads parts of the blockchain history is likely of little use, due to the potential for abuse of trust.

> **Comments:**
> **username_0**: I'm aware that a node might lie, and also aware of the light node concept. But, just like downloading a torrent file, you download it from different random users, therefor, if one node tried to give you a fake block, other nodes will also have to give you the exact fake block. which a very unlikely situation to happen, right?  
> **username_1**: *“Unlikely to happen”* generally isn’t the sort of security guarantee I’d want for my money. Why open yourself up to targeted attacks?  
> **username_0**: Really? because this is the model that blockchain uses as a security mechanism. An example of that is 51% attack, although it's a possibility, but it's unlikely to happen.  
> **username_1**: A 51% attack has a huge monetary cost, whereas an eclipse attack does not. So these two attacks are not analogous in this way; a 51% attack is **EXTREMELY** more unlikely.  

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