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Robert Kornacki 2019-07-22 15:29:16 -04:00
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@ -1,6 +1,8 @@
# PoW-SHA256
Rust crate which generates SHA256 Proofs of Work on serializable datatypes. Any type that implements `serde::Deserialize` can be used.
Rust crate which generates SHA256 Proofs of Work on serializable datatypes.
Any type that implements `serde::Deserialize` can be used.
This is a fork of the [`Pow` library](https://github.com/bddap/pow) by bddap with some new additions. Primary of these being:
@ -45,33 +47,16 @@ struct Block<T> {
}
```
# Score scheme
# Hashing Scheme
To score a proof of work for a given (target, PoW) pair:
Sha256 is calculated over the concatenation SALT + target + PoW.
The first 16 bytes of the hash are interpreted as a 128 bit unsigned integer.
That integer is the score.
A constant, 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
In other words:
The first 16 bytes of the resulting hash are interpreted as a 128 bit unsigned integer.
```rust
fn score<T: Serialize>(target: &T, PoW_tag: &PoW<T>) -> u128 {
let bytes = serialize(&SALT) + serialize(target) + serialize(PoW_tag);
let hash = sha256(&bytes);
deserialize(&hash[..16])
}
```
# Serialization encoding.
It shouldn't matter to users of this library, but the bincode crate is used for cheap
deterministic serialization. All values are serialized using network byte order.
# Threshold scheme
Given a minimum score m. A PoW p satisfies the minimum score for target t iff score(t, p) >= m.
A randomly generated constant, `SALT`, is used as prefix to prevent PoW reuse from other systems such as proof of work blockchains.
# Choosing a difficulty setting.
@ -102,4 +87,4 @@ fn average(difficulty: u128) -> u128 {
# License
This project is licensed under either of Apache License, Version 2.0 or MIT license, at your option.
This project is dual-licensed under `Apache License Version 2.0` & `MIT license`.