Blockchain

The goal for the assignment is to create a website that interfaces with the underlying blockchain. The blockchain will have a history of books that a user has inserted on the website.

The blockchain works on proof of stake. The peers join with an initial stake and based on the amount of stake, a peer will have a voting power. The voting power is a percentage of the total stake which is the sum of all the stake from every other peer. Each peer will have a chance proportional to their stake to propose a block . The selection for the block proposer is made by a round-robin deterministic algorithm which is based on the voting power of each peer. So, every round, each peer knows who should propose the new block. A new block is proposed every two new books added through the web interface. Since this blockchain is synchronous, after the block is proposed, the other peers will validate the block by checking the rootHash, the height, the prevHash, and match the new books with their current list of pending books. Afma is then run on the new proposed bock in order to make sure that every other peer has received the right block, isn't crashed, or is not byzantine.

Folders and Files

.
+-- _consensus
|   +-- peer.go
|   +-- go.mod
+-- _election
|   +-- election.go
|   +-- go.mod
+-- _keyshelper
|   +-- KeysHelper.go
|   +-- go.mod
+-- _server
|   +-- webserver.go
|  	+-- _blockchainweb
|   	+-- build
		+-- _src

Folders consensus: contains peer.go and the folder keys which is created on runtime for storing the private and public keys. election: contains the module election from election.go keyshelper: contains the module keyshelper from keyshelper.go server: contains the file webserver.go and the folder blockchainweb with inside build and src for the view of the website. Files -peer.go: This file contains all the code necessary to run a peer. -election.go:This file is used as a module for peer.go. It handles the proposers for the new blocks. -keyshelper.go:This module helps with handling the private and public keys. -webserver.go:This file runs the server for interfacing with the blockchain -Blocks.js:Is located in /server/blockchainweb/src and contains the code for handling the view for the website.

peer.go API

Other than the assignedPort which peer.go will listen to, it will also listen on assignedPort + 4000 for receiving new books and for showing the current state of the blockchain. The peer will accept post request on localhost:peerport+4000/block/new for adding new books and on localhost:peerport+4000/list for showing the current state of the blockchain.

webserver.go requests to peer.go

The webserver uses the list of peers which joined with stake that can be found on http://localhost:8080/validators. When new data is submitted, the webserver will relay the message to all peers. In order to populate the view for the current state of the blockchain, the webserver asks to every peer on localhost:peerport+4000/list. If all the latest heights and the root hashes match, the view is populated.

Usage

Files to run: webserver.go peer.go

There are no flags required for webserver.go

For peer.go, the program needs different flags:

-i: the peer number. -n: the maximum number of peers. -p: the port number. -s: the stake amount

Optional flags

-v: verbose.

Example

For the web interface cd server && go run webserver.go

For the peers cd consensus

go run peer.go -i 0 -n 4 -p 41000 -s 120

go run peer.go -i 1 -n 4 -p 41004 -s 400

go run peer.go -i 2 -n 4 -p 41008 -s 320

go run peer.go -i 3 -n 4 -p 41012 -s 120

Test by visiting http://localhost:8080/ Insert the fields for the adding a book: Title, Author, Pages, Year. Then Submit The blocks are created every two books added. So, add at least two books to see the new state of the blockchain.