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//! MCaptch's SHA256 based Proof of Work library
//!
//! # Example:
//! ```rust
//! use pow_sha256::{ConfigBuilder, PoW};
//!
//! fn main() {
//! let config = ConfigBuilder::default()
//! .salt("myrandomsaltisnotlongenoug".into())
//! .build()
//! .unwrap();
//!
//! let phrase = "ironmansucks";
//!
//! const DIFFICULTY: u32 = 1000;
//!
//! let work = config.prove_work(&phrase, DIFFICULTY).unwrap();
//! assert!(config.is_valid_proof(&work, &phrase));
//! assert!(config.is_sufficient_difficulty(&work, DIFFICULTY));
//! }
//! ```
use std::marker::PhantomData;
use derive_builder::Builder;
//use num::Num;
use serde::{Deserialize, Serialize};
use sha2::{digest::Update, Digest, Sha256};
/// Proof of Work over concrete type T. T can be any type that implements serde::Serialize.
#[derive(Serialize, Builder, Deserialize, PartialEq, Clone, Debug)]
pub struct PoW<T> {
pub nonce: u64,
pub result: String,
#[builder(default = "PhantomData", setter(skip))]
_spook: PhantomData<T>,
}
/// Configuration for generting proof of work
/// Please choose a long, unique value for salt
/// Resistance to dictionary/rainbow attacks depend on uniqueness
/// of the salt
#[derive(Serialize, Deserialize, Builder, PartialEq, Clone, Debug)]
pub struct Config {
pub salt: String,
}
/// Return value of incremental prooving. When proof is ready, IncrementalSolve::Work is returned
/// and when proof is not ready, IncrementalSolve::Intermediate is returned
#[cfg(feature = "incremental")]
pub enum IncrementalSolve<T> {
/// Intermediate result
Intermediate(u128, u64, Sha256, u128),
/// Final result
Work(PoW<T>),
}
impl Config {
///
/// step is used to control the number of cycles after which the function should exit, even
/// when the proof isn't ready
/// inter is used to keep track of state and complete proof generation. Set inter to None
/// during first cyle and pass the returned value of the previous cycle to continue proof
/// generation
#[cfg(feature = "incremental")]
pub fn stepped_prove_work<T>(
&self,
t: &T,
difficulty: u32,
step: usize,
inter: Option<IncrementalSolve<T>>,
) -> bincode::Result<IncrementalSolve<T>>
where
T: Serialize,
{
bincode::serialize(t)
.map(|v| self.stepped_prove_work_serialized(&v, difficulty, step, inter))
}
#[cfg(feature = "incremental")]
/// Create Proof of Work over item of type T.
///
/// Make sure difficulty is not too high. A 64 bit difficulty,
/// for example, takes a long time on a general purpose processor.
/// The input is assumed to be serialized using network byte order.
///
/// Make sure difficulty is not too high. A 64 bit difficulty,
/// for example, takes a long time on a general purpose processor.
/// step is used to control the number of cycles after which the function should exit, even
/// when the proof isn't ready
/// inter is used to keep track of state and complete proof generation. Set inter to None
/// during first cyle and pass the returned value of the previous cycle to continue proof
/// generation
/// Returns bincode::Error if serialization fails.
/// Create Proof of Work on an already serialized item of type T.
fn stepped_prove_work_serialized<T>(
&self,
prefix: &[u8],
difficulty: u32,
step: usize,
inter: Option<IncrementalSolve<T>>,
) -> IncrementalSolve<T>
where
T: Serialize,
{
let (mut result, mut n, prefix_sha, difficulty) = match inter {
Some(IncrementalSolve::Intermediate(result, nonce, prefix, difficulty)) => {
(result, nonce, prefix, difficulty)
}
_ => {
let prefix_sha = Sha256::new().chain(&self.salt).chain(prefix);
let n = 0;
let result = 0;
let difficulty = get_difficulty(difficulty);
(result, n, prefix_sha, difficulty)
}
};
let mut count = 0;
while result < difficulty {
if count > step {
return IncrementalSolve::Intermediate(result, n, prefix_sha, difficulty);
} else {
count += 1;
}
n += 1;
result = dev::score(prefix_sha.clone(), n);
}
IncrementalSolve::Work(PoW {
nonce: n,
result: result.to_string(),
_spook: PhantomData,
})
}
/// Create Proof of Work over item of type T.
///
/// Make sure difficulty is not too high. A 64 bit difficulty,
/// for example, takes a long time on a general purpose processor.
/// Returns bincode::Error if serialization fails.
pub fn prove_work<T>(&self, t: &T, difficulty: u32) -> bincode::Result<PoW<T>>
where
T: Serialize,
{
bincode::serialize(t).map(|v| self.prove_work_serialized(&v, difficulty))
}
/// Create Proof of Work on an already serialized item of type T.
/// The input is assumed to be serialized using network byte order.
///
/// Make sure difficulty is not too high. A 64 bit difficulty,
/// for example, takes a long time on a general purpose processor.
pub fn prove_work_serialized<T>(&self, prefix: &[u8], difficulty: u32) -> PoW<T>
where
T: Serialize,
{
let prefix_sha = Sha256::new().chain(&self.salt).chain(prefix);
let mut n = 0;
let mut result = 0;
let difficulty = get_difficulty(difficulty);
while result < difficulty {
n += 1;
result = dev::score(prefix_sha.clone(), n);
}
PoW {
nonce: n,
result: result.to_string(),
_spook: PhantomData,
}
}
/// Calculate the PoW score with the provided input T.
pub fn calculate<T>(&self, pow: &PoW<T>, t: &T) -> bincode::Result<u128>
where
T: Serialize,
{
bincode::serialize(t).map(|v| self.calculate_serialized(pow, &v))
}
/// Calculate the PoW score of an already serialized T and self.
/// The input is assumed to be serialized using network byte order.
pub fn calculate_serialized<T>(&self, pow: &PoW<T>, target: &[u8]) -> u128
where
T: Serialize,
{
dev::score(Sha256::new().chain(&self.salt).chain(target), pow.nonce)
}
/// Verifies that the PoW is indeed generated out of the phrase provided.
pub fn is_valid_proof<T>(&self, pow: &PoW<T>, t: &T) -> bool
where
T: Serialize,
{
match self.calculate(pow, t) {
Ok(res) => {
return if pow.result == res.to_string() {
true
} else {
false
}
}
Err(_) => return false,
}
}
/// Checks if the PoW result is of sufficient difficulty
pub fn is_sufficient_difficulty<T>(&self, pow: &PoW<T>, target_diff: u32) -> bool
where
T: Serialize,
{
match pow.result.parse::<u128>() {
Ok(res) => return res >= get_difficulty(target_diff),
Err(_) => return false,
}
}
}
pub mod dev {
use super::*;
pub fn score(prefix_sha: Sha256, nonce: u64) -> u128 {
first_bytes_as_u128(
prefix_sha
.chain(&nonce.to_string()) //used to be: to_be_bytes() converts to network endian
// chain() expexets something that can be converted to &[u8], String is fine
.finalize()
.as_slice(),
)
}
/// # Panics
///
/// panics if inp.len() < 16
fn first_bytes_as_u128(inp: &[u8]) -> u128 {
use bincode::config::*;
DefaultOptions::new()
.with_fixint_encoding()
.allow_trailing_bytes()
.with_no_limit()
.with_big_endian()
.deserialize(&inp)
.unwrap()
}
}
// utility function to get u128 difficulty factor from u32
// javacript isn't capable of represnting u128 so
fn get_difficulty(difficulty_factor: u32) -> u128 {
u128::max_value() - u128::max_value() / difficulty_factor as u128
}
#[cfg(test)]
mod test {
use super::*;
const DIFFICULTY: u32 = 1000;
fn get_config() -> Config {
ConfigBuilder::default()
.salt(
"79ziepia7vhjgviiwjhnend3ofjqocsi2winc4ptqhmkvcajihywxcizewvckg9h6gs4j83v9".into(),
)
.build()
.unwrap()
}
#[test]
fn base_functionality() {
// Let's prove we did work targeting a phrase.
let phrase = b"Ex nihilo nihil fit.".to_vec();
let config = get_config();
let pw = config.prove_work(&phrase, DIFFICULTY).unwrap();
assert!(config.calculate(&pw, &phrase).unwrap() >= get_difficulty(DIFFICULTY));
assert!(config.is_valid_proof(&pw, &phrase));
assert!(config.is_sufficient_difficulty(&pw, DIFFICULTY));
}
#[test]
fn double_pow() {
let phrase = "Ex nihilo nihil fit.".to_owned();
let config = get_config();
let pw = config.prove_work(&phrase, DIFFICULTY).unwrap();
let pwpw = config.prove_work(&pw, DIFFICULTY).unwrap();
assert!(config.calculate(&pw, &phrase).unwrap() >= get_difficulty(DIFFICULTY));
assert!(config.is_valid_proof(&pw, &phrase));
assert!(config.is_sufficient_difficulty(&pw, DIFFICULTY));
assert!(config.calculate(&pwpw, &pw).unwrap() >= get_difficulty(DIFFICULTY));
assert!(config.is_valid_proof(&pwpw, &pw));
assert!(config.is_sufficient_difficulty(&pwpw, DIFFICULTY));
}
#[test]
fn is_not_valid_proof() {
let phrase = "Ex nihilo nihil fit.".to_owned();
let phrase2 = "Omne quod movetur ab alio movetur.".to_owned();
let config = get_config();
let pw = config.prove_work(&phrase, DIFFICULTY).unwrap();
let pw2 = config.prove_work(&phrase2, DIFFICULTY).unwrap();
assert!(!config.is_valid_proof(&pw, &phrase2));
assert!(!config.is_valid_proof(&pw2, &phrase));
}
fn check_time(prev: u128, current: u128) -> bool {
if prev < current {
true
} else {
false
}
}
#[test]
fn computation_time_test() {
use std::time::Instant;
const DIFFICULTY: u32 = 50000;
let target = "testing";
let config = get_config();
let mut current = Instant::now();
config.prove_work(&target, DIFFICULTY).unwrap();
let prev = current.elapsed().as_nanos();
current = Instant::now();
config.prove_work(&target, DIFFICULTY * 10).unwrap();
let tmp = current.elapsed().as_nanos();
assert!(check_time(prev, tmp));
}
#[test]
fn serialization_test() {
let target: u8 = 1;
let config = get_config();
let pw = config.prove_work(&target, DIFFICULTY).unwrap();
let message: (u8, PoW<u8>) = (target, pw);
let message_ser = bincode::serialize(&message).unwrap();
let recieved_message: (u8, PoW<u8>) = bincode::deserialize(&message_ser).unwrap();
assert_eq!(recieved_message, message);
assert!(config.is_sufficient_difficulty(&message.1, DIFFICULTY));
assert!(config.is_valid_proof(&message.1, &target));
}
#[test]
#[cfg(feature = "incremental")]
fn stepped_solve() {
let phrase = "Ex nihilo nihil fit.".to_owned();
let config = get_config();
let mut inter = None;
loop {
match config.stepped_prove_work(&phrase, 50000, 1000, inter) {
Ok(IncrementalSolve::Intermediate(result, nonce, prefix, difficulty)) => {
println!("Current nonce {nonce}");
inter = Some(IncrementalSolve::Intermediate(
result, nonce, prefix, difficulty,
));
continue;
}
Ok(IncrementalSolve::Work(w)) => {
assert!(config.is_valid_proof(&w, &phrase));
assert!(config.is_sufficient_difficulty(&w, DIFFICULTY));
break;
}
Err(e) => panic!("{}", e),
};
}
}
}