Really fast Proof of Work for javascript

Emscripten + Wasm. It is designed to not freeze the browser when doing this by limiting it to 100ms per calculation cycle. This can be changed in the maxMS class variable.

Also the wasm file is packed inside the JS using magic.

Proof of work syntax:

Calculating on browser:

// Token can be any size, I just used a UUID here.
const token = new Uint8Array([188, 114, 93, 192, 195, 150, 75, 93, 183, 49, 207, 134, 124, 48, 25, 171]);
const difficulty = 4;

ProofOfWork(token, difficulty).then(result=>{
    result.solveAsync().then(e=>{
        console.log("Solved Proof of Work: ", e);
    });
});

Testing on server:

import hashlib
import struct

sPOWFooter = struct.compile(">BI")
def TestProofOfWork(data, difficulty, nonce):
    test = hashlib.sha512(data + sPOWFooter.pack(difficulty, nonce)).hexdigest()
    if test[:difficulty] == "0"*difficulty:
        return True
    return False