Merkle Patricia Tries (2x)

[rodoufu]

An experimental plugin for persisting neo blockchain states into Merkle Patricia Tries.

[igormcoelho]

Very good Rodolfo! Let's advance with this plugin. The target is still neo-project:master, could you change it for neo-project:master-2.x ?

[vncoelho]

Great job, @rodoufu.
Lets create this branch here, Igor.

[erikzhang]

Is this the same as neo-project/neo#528?

[igormcoelho]

Right now it's the same Erik, but it will change... this one here will be more experimental, so that we validate it and then port it to neo project.

[rodoufu]

Very good Rodolfo! Let's advance with this plugin. The target is still neo-project:master, could you change it for neo-project:master-2.x ?

@igormcoelho , it looks like there's no mater-2x branch on the neo-plugins project:
https://github.com/neo-project/neo-plugins/branches

Only on the core neo project:
https://github.com/neo-project/neo/branches

Am I missing something?

[rodoufu]

Now I have changed the target.

[shargon]

is on master-2.x , this feature will be for neo 3

[erikzhang]

I think this plugin is for 2.x, because 2.x has no built-in MPT.

[shargon]

Throw an exception on empty tree

[igormcoelho]

I think node types are verified before usage.. IsNull for example, has no Key.

[shargon]

is not possible to be bigger than 256?

[igormcoelho]

It's possible, just an effect of using SHA256. In fact, we should use Hash256, to avoid length attacks.

[rodoufu]

@shargon , I think the idea is to have the MPT on Neo version 3.0 but start it as a plugin in the version 2.x so we can use it and improve before going to the Neo 3.0

[igormcoelho]

@shargon
A node can be of four kinds:

• Null (size 0)
• Hash (size 1) (I don't know if Rodolfo considered this as a node... but I did on mine)
• Path (size 2) it can be Leaf or Extension. Rodolfo added the Key to Leaf, to avoid colisions, I think we can do that implicitly Rodolfo, without hardcoding the key (so size is effectly 2 and no space is wasted twice)
  -Branch (size 17) I used variable sizes from 3 to 17 on my implementation (3 is Branch2 + Leaf, and 17 is classic Branch16 + Leaf). This slightly compresses the tree.

@rodoufu
As soon as you're back, we need to implement Sparse Merkle Tree, which is a binary tree, and allows much deeper compression techniques. I believe space will be further reduced than MPT.
We can create another plugin with that other tree and compare both, so Neo 3.0 can take a clear decision.
MPT and SMT solve the same problem: validated key-value storage with inclusion and non-inclusion proofs.

[vncoelho]

@rodoufu, this has been a great effort. Thanks for all your motivation, studies and prototype on this.
NeoX has already been merged to master2x with another implementation.
In this sense, I will close this one.

However, I would like to state my real appreciation for the work you conducted.