blockchain

Educational Python Implementation of a Blockchain

Prerequisites

• Python
• Flask
• Requests
• Mnemonic
• ECDSA

Basic Installation (Ubuntu)

Install python:

sudo apt install python

and then the packages using python's package manager (pip):

pip install flask requests mnemonic ecdsa

REST API

Node Endpoints

Endpoint	HTTP Verb	Request (JSON)	Response (JSON)	Description
/	POST	Node (opt.)	Node	Check if node is reachable/online
/nodes/	GET	Node (opt.)	Nodes array	Retrieve all known nodes
/nodes/nid/	GET	-	Node	Retrieve node by nid
/nodes/	POST	Node	Nodes array	Add node to known nodes
/nodes/	DELETE	Node	Nodes array	Remove node from known nodes

Using "random" as the nid returns a random node. Otherwise, nid is the node index.

Blockchain Endpoints

Endpoint	HTTP Verb	Request (JSON)	Response (JSON)	Description
/blockchain/	GET	-	Blockchain Info	Retrieve blockchain information
/blockchain/	PUT	Blockchain Info	Blockchain Info	Replace blockchain information

Transaction Endpoints

Endpoint	HTTP Verb	Request (JSON)	Response (JSON)	Description
/transactions/	GET	-	Transactions Header	Retrieve unconfirmed transactions header
/transactions/tid/	GET	-	Transaction	Retrieve unconfirmed transaction by tid
/transactions/	POST	Transaction	Transaction	Post new transaction
/transactions/	DELETE	Transaction	Transaction	Remove posted transaction

For tid both the index and the hash can be used.

Block Endpoints

Endpoint	HTTP Verb	Request (JSON)	Response (JSON)	Description
/blocks/bid/	GET	-	Block Header	Retrieve block header by block id
/blocks/bid/transactions/	GET	-	Transactions Header	Retrieve block transactions header by block id
/blocks/bid/transactions/tid/	GET	-	Transaction	Retrieve block transaction by bid-tid pair
/blocks/bid/transactions/tid/inputs/	GET	-	Transaction input array	Retrieve block transaction inputs by bid-tid pair
/blocks/bid/transactions/tid/inputs/iid/	GET	-	Transaction input	Retrieve block transaction input by bid-tid-iid
/blocks/bid/transactions/tid/outputs/	GET	-	Transaction output array	Retrieve block transaction outputs by bid-tid pair
/blocks/bid/transactions/tid/outputs/oid/	GET	-	Transaction output	Retrieve block transaction output by bid-tid-oid
/blocks/	POST	Block Header	-	Create block from header and unconfirmed transactions

Using "last" as the bid returns information for the last block in the chain. Otherwise, bid is the block height.

For tid both the index and the hash can be used.

UTXO Endpoints

Endpoint	HTTP Verb	Request (JSON)	Response (JSON)	Description
/utxo/address/	GET	-	UTXO	Retrieve utxo by address
/utxo/address/outputs/	GET	-	UTXO Output array	Retrieve utxo outputs by address
/utxo/address/outputs/transaction_hash/	GET	-	UTXO Output	Retrieve utxo output by address-hash pair
/utxo/address/	POST	UTXO (opt.)	UTXO	Create utxo of address
/utxo/address/outputs/	POST	UTXO Output	UTXO Output	Add utxo output to utxo of address
/utxo/address/outputs/	DELETE	UTXO Output	UTXO Output	Remove utxo output from utxo of address

How To Use

DNS Server

Start at least one dns server using:

python dns_server.py

which by default runs on port 42020.

Full Nodes

Start at least one full node using:

python full_node.py -d ../.full_nodeX

where X should be different for each full node, so that the directories don't overlap.

Miners

Start at least one miner using:

python miner.py -ra reward_address

where the reward_address could be the address generated by some full node or the testing script.

Testing (Transaction Posting)

Execute the testing script using:

python testing.py

in order to post a correctly formed transaction.

Of course there needs to be an UTXO entry for that address, so that the transaction can be formed. So, using the testing script's address as a reward address of some miner might be a good idea to get going!

Future Ideas

• Blockchain Explorer
• GUI Wallet
• Light Nodes (light-weight version of the Full Node, which doesn't keep the whole blockchain)
• Super Nodes (Nodes that get rewarded for keeping the whole blockchain and confirming blocks and transactions)
• Proof-of-Work Consensus (actual implementation with adaptive difficulty)
• Proof-of-Stake Consensus (maybe even hybrid schemes)