A Simple Blockchain. Written in Rust.
I need a similar data structure for a future Rust project, so I figured I should create a simple blockchain implementation to get familiar with it. I also explain what happens in each method for my own reference.
See the Installation and then Running asb sections to run this demo.
Each Block within the Blockchain contains:
- The SHA256 hash of the
Block - Data - in this case a
String, for simplicity's sake - An index indicating the block's position within the
Blockchain - A nonce - a one-use number generated by the Proof of Work algorithm
- The SHA256 hash of the previous
Blockin theBlockchain - A timestamp indicating the
Block's inception
This is the struct definition:
#[derive(Debug)]
pub struct Block {
pub block_hash: String,
data: String,
index: usize,
nonce: usize,
previous_hash: String,
timestamp: String,
}block_hash is pub since it will be stored in the Blockchain's transactions Vec when the Block is added.
I then defined some methods to calculate the hash of each Block. Let's go over them one by one.
impl Block {
fn is_valid_hash(&self, difficulty: usize, hash: &str) -> bool {
let pattern = &"0".repeat(difficulty);
hash.starts_with(pattern)
}is_valid_hash() checks whether the hash begins with repeating 0s. 0 is repeated n times, depending on the difficulty value. This method then returns a boolean value depending on whether hash matches the prefix defined by pattern.
fn get_hash_string(&self) -> String {
let mut hash_string = self.index.to_string();
hash_string.push_str(&self.data);
hash_string.push_str(&self.timestamp);
hash_string.push_str(&self.previous_hash);
hash_string
}To calculate the hash, all data excluding the block_hash and nonce contained within the Block is concatenated into a String. get_hash_string() does exactly this.
// Imports at the top of `block.rs`.
use data_encoding::HEXLOWER;
use ring::digest::{
Context,
SHA256
};
fn get_hash(hash_string: &str) -> String {
let mut context = Context::new(&SHA256);
context.update(hash_string.to_string().as_bytes());
HEXLOWER.encode(context.finish().as_ref())
}get_hash() then takes the String returned from get_hash_string() and calculates the hash. This is returned in the form of a String.
fn mine_block(&mut self, difficulty: usize) {
let mut hash = String::new();
let mut nonce: usize = 0;
while !self.is_valid_hash(difficulty, &hash) {
nonce += 1;
let mut temp_hash_string = self.get_hash_string();
temp_hash_string.push_str(&nonce.to_string());
hash = Block::get_hash(&temp_hash_string);
}
self.block_hash = hash;
self.nonce = nonce;
}mine_block() is where the Proof of Work happens.
I initialize the hash to an empty String, and the nonce to 0. The hash is continuously checked against the pattern by calling the previously defined is_valid_hash() method.
While the hash does not match the correct pattern, a new hash is calculated by concatenating the incremented nonce with the target string returned by get_hash_string().
If the hash matches the correct pattern, the block_hash and nonce are set within the Block.
// Import at the top of `block.rs`.
use chrono::prelude::Local;
pub fn new(data: &str, difficulty: usize, index: usize, previous_hash: &str) -> Block {
let mut new_block = Block{
index: index,
block_hash: "".to_string(),
data: String::from(data),
timestamp: Local::now().format("%m-%d-%Y %H:%M:%S").to_string(),
previous_hash: String::from(previous_hash),
nonce: 0
};
new_block.mine_block(difficulty);
new_block
}
}new() will return a new Block after calculating its block_hash and nonce by calling the previously defined mine_block() method.
A Blockchain contains:
- A
Vecwhich holdsBlocks - A difficulty level which is used when calculating the
Block'sblock_hashandnonce - A
Vecwhich holds the SHA256 hashes of eachBlock
This is the struct definition:
// Import at the top of `blockchain.rs`.
use crate::block::Block;
#[derive(Debug)]
pub struct Blockchain {
pub chain: Vec<Block>,
difficulty: usize,
transactions: Vec<String>
}I then defined some methods to initialize a new Blockchain. Let's go over them one by one.
impl Blockchain {
pub fn new(difficulty: usize) -> Blockchain {
let genesis = Block::new("Genesis Block", difficulty, 0, &"0".repeat(64));
let genesis_hash = genesis.block_hash.clone().to_string();
Blockchain{
chain: vec![genesis],
difficulty: difficulty,
transactions: vec![genesis_hash]
}
}new() creates a new Blockchain with a genesis block. The genesis block is the first Block in the chain Vec. Its hash is also the first hash in the transactions Vec.
pub fn add_block(&mut self, data: String) {
let last_block = &self.chain[self.chain.len() - 1];
let previous_hash = &last_block.block_hash;
let new_block = Block::new(&data, self.difficulty, self.chain.len(), previous_hash);
self.transactions.push(new_block.block_hash.clone().to_string());
self.chain.push(new_block);
}
}I just defined one more method, add_block(), which will obviously add a new Block to the Blockchain. The new Block's block_hash and nonce are calculated based on the difficulty value set in the Blockchain struct.
The new Block and its hash are then pushed onto the chain and transactions Vecs respectively.
You will need Rust installed on your computer.
cargo build --release
Then check if the asb binary compiled correctly:
On Linux or Mac:
./target/release/asb -V
On Windows:
./target/release/asb.exe -V
Binaries are attached to each release in the Releases section.
usage: asb
[-d <difficulty>]
[-t <total-blocks>]
Set the difficulty level with the -d flag. The default value is 5.
Set the total number of blocks in the blockchain with the -t flag. The default value is 5.
Command:
$ asb
Output:
INITIALIZING BLOCKCHAIN
=======================
SETTING DIFFICULTY LEVEL OF 5
Creating genesis block
Calculating valid hash for genesis block...
Done.
ADDING 4 BLOCKS TO THE BLOCKCHAIN
Adding block #1
Calculating valid hash for block 1...
Done.
Adding block #2
Calculating valid hash for block 2...
Done.
Adding block #3
Calculating valid hash for block 3...
Done.
Adding block #4
Calculating valid hash for block 4...
Done.
DISPLAYING BLOCKCHAIN METADATA
==============================
TRANSACTIONS
------------
SHA256: 000002ef9b8faa31df2ffca79ea7a40e8fb99bf6d0218fc41af2a9460b69cae9
SHA256: 00000dc727c2ad0d4e0651f04697729c19f3bfeaf0fde13d22d138390c032b2f
SHA256: 000004c1f922033e6cdc2e81b1786a5e2f9c056b7720eebf922bbff257815611
SHA256: 00000d693810e04371b7b7d78cd0decee2c69def64960fca5bfa5109cb05ea9c
SHA256: 000007378b30eb3af6fbbf79a0b730eccae2a7e94af2a59b7ede3f1538eafdf1
BLOCKS
------
GENESIS BLOCK
hash: 000002ef9b8faa31df2ffca79ea7a40e8fb99bf6d0218fc41af2a9460b69cae9
data: "Genesis Block"
index: 0
nonce: 246429
previous hash: 0000000000000000000000000000000000000000000000000000000000000000
timestamp: 07-23-2021 03:47:23
BLOCK 1
hash: 00000dc727c2ad0d4e0651f04697729c19f3bfeaf0fde13d22d138390c032b2f
data: "BLOCK 1"
index: 1
nonce: 35498
previous hash: 000002ef9b8faa31df2ffca79ea7a40e8fb99bf6d0218fc41af2a9460b69cae9
timestamp: 07-23-2021 03:47:23
BLOCK 2
hash: 000004c1f922033e6cdc2e81b1786a5e2f9c056b7720eebf922bbff257815611
data: "BLOCK 2"
index: 2
nonce: 3279400
previous hash: 00000dc727c2ad0d4e0651f04697729c19f3bfeaf0fde13d22d138390c032b2f
timestamp: 07-23-2021 03:47:23
BLOCK 3
hash: 00000d693810e04371b7b7d78cd0decee2c69def64960fca5bfa5109cb05ea9c
data: "BLOCK 3"
index: 3
nonce: 941862
previous hash: 000004c1f922033e6cdc2e81b1786a5e2f9c056b7720eebf922bbff257815611
timestamp: 07-23-2021 03:47:28
BLOCK 4
hash: 000007378b30eb3af6fbbf79a0b730eccae2a7e94af2a59b7ede3f1538eafdf1
data: "BLOCK 4"
index: 4
nonce: 2277566
previous hash: 00000d693810e04371b7b7d78cd0decee2c69def64960fca5bfa5109cb05ea9c
timestamp: 07-23-2021 03:47:30
FINISHED CREATING BLOCKCHAIN WITH 5 BLOCKS IN 10 SECONDS.
Command:
$ asb -d 6 -t 3
Output:
INITIALIZING BLOCKCHAIN
=======================
SETTING DIFFICULTY LEVEL OF 6
Creating genesis block
Calculating valid hash for genesis block...
Done.
ADDING 2 BLOCKS TO THE BLOCKCHAIN
Adding block #1
Calculating valid hash for block 1...
Done.
Adding block #2
Calculating valid hash for block 2...
Done.
DISPLAYING BLOCKCHAIN METADATA
==============================
TRANSACTIONS
------------
SHA256: 000000f915a0ed32185029b7c740a7113a5535ffc63b669fe1f392faec95ce22
SHA256: 000000ff34769d20b4ea5ed87dd6ab9758796c9255424b4d3b57856a3d3a73bd
SHA256: 00000051fc46f747d87944feb22401fa401398e2fdabda0a13e96b638336c435
BLOCKS
------
GENESIS BLOCK
hash: 000000f915a0ed32185029b7c740a7113a5535ffc63b669fe1f392faec95ce22
data: "Genesis Block"
index: 0
nonce: 25611139
previous hash: 0000000000000000000000000000000000000000000000000000000000000000
timestamp: 07-23-2021 03:49:20
BLOCK 1
hash: 000000ff34769d20b4ea5ed87dd6ab9758796c9255424b4d3b57856a3d3a73bd
data: "BLOCK 1"
index: 1
nonce: 4520028
previous hash: 000000f915a0ed32185029b7c740a7113a5535ffc63b669fe1f392faec95ce22
timestamp: 07-23-2021 03:50:01
BLOCK 2
hash: 00000051fc46f747d87944feb22401fa401398e2fdabda0a13e96b638336c435
data: "BLOCK 2"
index: 2
nonce: 50128421
previous hash: 000000ff34769d20b4ea5ed87dd6ab9758796c9255424b4d3b57856a3d3a73bd
timestamp: 07-23-2021 03:50:08
FINISHED CREATING BLOCKCHAIN WITH 3 BLOCKS IN 123 SECONDS.
Command:
$ asb -d 3 -t 6
Output:
INITIALIZING BLOCKCHAIN
=======================
SETTING DIFFICULTY LEVEL OF 3
Creating genesis block
Calculating valid hash for genesis block...
Done.
ADDING 5 BLOCKS TO THE BLOCKCHAIN
Adding block #1
Calculating valid hash for block 1...
Done.
Adding block #2
Calculating valid hash for block 2...
Done.
Adding block #3
Calculating valid hash for block 3...
Done.
Adding block #4
Calculating valid hash for block 4...
Done.
Adding block #5
Calculating valid hash for block 5...
Done.
DISPLAYING BLOCKCHAIN METADATA
==============================
TRANSACTIONS
------------
SHA256: 000b112ffe3d23ab19717397ca86eb9cea1c4961c92e3c8e354a6a2ce21d7e6e
SHA256: 000a22a4c8f82fd5036213b67827d39d334670cfe6f83933ade1ec816984368a
SHA256: 000788050d9eb1e4ad38d00497842733375737a86dd0af7ce6f6c6562b3b7e93
SHA256: 00019fffd8991621d28e51a68c603088070f917894e81d73d54cac0e42eda03a
SHA256: 0004900e7daa43cf8b9b914e7056e0353aead7accc0f935a7920d790c599c466
SHA256: 00012b9f667c95cd3abc9bb879f5b2a0c7de2fac5681825e508e3eb210058396
BLOCKS
------
GENESIS BLOCK
hash: 000b112ffe3d23ab19717397ca86eb9cea1c4961c92e3c8e354a6a2ce21d7e6e
data: "Genesis Block"
index: 0
nonce: 5439
previous hash: 0000000000000000000000000000000000000000000000000000000000000000
timestamp: 07-23-2021 03:53:13
BLOCK 1
hash: 000a22a4c8f82fd5036213b67827d39d334670cfe6f83933ade1ec816984368a
data: "BLOCK 1"
index: 1
nonce: 5361
previous hash: 000b112ffe3d23ab19717397ca86eb9cea1c4961c92e3c8e354a6a2ce21d7e6e
timestamp: 07-23-2021 03:53:13
BLOCK 2
hash: 000788050d9eb1e4ad38d00497842733375737a86dd0af7ce6f6c6562b3b7e93
data: "BLOCK 2"
index: 2
nonce: 3743
previous hash: 000a22a4c8f82fd5036213b67827d39d334670cfe6f83933ade1ec816984368a
timestamp: 07-23-2021 03:53:13
BLOCK 3
hash: 00019fffd8991621d28e51a68c603088070f917894e81d73d54cac0e42eda03a
data: "BLOCK 3"
index: 3
nonce: 202
previous hash: 000788050d9eb1e4ad38d00497842733375737a86dd0af7ce6f6c6562b3b7e93
timestamp: 07-23-2021 03:53:13
BLOCK 4
hash: 0004900e7daa43cf8b9b914e7056e0353aead7accc0f935a7920d790c599c466
data: "BLOCK 4"
index: 4
nonce: 79
previous hash: 00019fffd8991621d28e51a68c603088070f917894e81d73d54cac0e42eda03a
timestamp: 07-23-2021 03:53:13
BLOCK 5
hash: 00012b9f667c95cd3abc9bb879f5b2a0c7de2fac5681825e508e3eb210058396
data: "BLOCK 5"
index: 5
nonce: 197
previous hash: 0004900e7daa43cf8b9b914e7056e0353aead7accc0f935a7920d790c599c466
timestamp: 07-23-2021 03:53:13
FINISHED CREATING BLOCKCHAIN WITH 6 BLOCKS IN 0 SECONDS.