Crates.io | mcaptcha_pow_sha256 |

lib.rs | mcaptcha_pow_sha256 |

version | 0.5.0 |

source | src |

created_at | 2023-10-14 18:28:23.525936 |

updated_at | 2023-10-28 21:06:53.270232 |

description | SHA256 PoW on any serializable datatype used in mCaptcha |

homepage | |

repository | https://git.batsense.net/mCaptcha/mcaptcha_pow_sha256 |

max_upload_size | |

id | 1003249 |

size | 57,753 |

**NOTE: All versions prior to 0.3.1 produce broken PoWs, upgrade to
latest version**

mcaptcha_pow_sha256 is a copy of

`pow_sha256`

by robkorn which is a modified version of`pow`

library. All copyrights belong to the original authors.

Rust crate which generates SHA256 Proofs of Work on serializable datatypes.

Whether for blockchain-related projects or Hashcash-like schemes, this
crate can be used to prove work was done on a given serializable input.
The input merely needs to implement `serde::Deserialize`

to be used.

This is a fork of the `pow`

library by
@robkorn) with some new
additions. Primary of these being:

- PoW datatype now offers a constructor
- Salt is no longer hard coded into the library, users can provide unique salts.

Other small changes have also been included of various importance but mostly just stylistic/ease of use improvements.

https://docs.rs/mcaptcha_pow_sha256

Prove work specifically targeting a phrase.

```
use mcaptcha_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.calculate(&work, &phrase).unwrap() >= DIFFICULTY);
assert!(config.is_valid_proof(&work, &phrase));
assert!(config.is_sufficient_difficulty(&work, DIFFICULTY));
}
```

Prove more difficult work. This time targeting a time.

```
// Greater difficulty this time around. Takes around 100,000 hashes
// to find a nonce of the correct difficulty.
use mcaptcha_pow_sha256::{ConfigBuilder, PoW};
fn main() {
let config = ConfigBuilder::default()
.salt("myrandomsaltisnotlongenoug".into())
.build()
.unwrap();
let phrase = "ironmansucks";
const DIFFICULTY: u32 = 100_000;
let work = config.prove_work(&phrase, DIFFICULTY).unwrap();
assert!(config.calculate(&work, &phrase).unwrap() >= DIFFICULTY);
assert!(config.is_valid_proof(&work, &phrase));
assert!(config.is_sufficient_difficulty(&work, DIFFICULTY));
}
```

`SALT`

is used as prefix to prevent PoW reuse from other systems such as
proof of work blockchains.

SHA256 is calculated over the concatenation of the:

- SALT
- Serialized Input
`T`

- Nonce

The first 16 bytes of the resulting hash are interpreted as a 128 bit unsigned integer and saved as the final result.

Depending on your use case, difficulty settings often are best set dynamically a la bitcoin.

However if your use case requires manual setting then it is trivial to set one yourself. One way to do so is to choose the average number of hashes desired with a function like this:

```
fn get_difficulty(average: u128) -> u128 {
debug_assert_ne!(average, 0, "It is impossible to prove work in zero attempts.");
let m = u128::max_value();
m - m / average
}
```

Conversely we can use the same equation to calculate the probable number of hashes required to satisfy a given difficulty:

```
fn est_average(difficulty: u128) -> u128 {
let m = u128::max_value();
if difficulty == m {
return m;
}
m / (m - difficulty)
}
```

See CHANGELOG.md

This project is dual-licensed under `Apache License Version 2.0`

or `MIT license`

.

2023 development is funded through the NGI0 Entrust Fund, via NLnet. Please see here for more details.