pow-php-wasm-demo

This repository is proof of concept that implement proof of work system in PHP, javascript, and web assembly.

Screenshots

Server web deny content for customer request without submit proof of work solution

Customer solve proof of work at 43480 hash/sec

Customer submit proof of work solution and server web accept

Server web show content for customer with submit proof of work solution

Getting Started

Drop the files contained in this repository in server (example /var/www) and configure your server web with new virtual host with document root is the htdocs directory of this repository. It notice that want settings.php be locate outside document root.

Hash function

Pass the values (in order) to SHA256 twice, like bitcoin

1. hostname - the hostname of your server $_SERVER['HTTP_HOST']
2. timestamp - a current iso-8601 timestamp in UTC
3. rand - the random string put by the server and stored to $_SESSION['pow']['rand']
4. counter - a nonce that is incremented until the hash satisfies the difficulty

Prevent cheater customer

Cheater customer prevent by

1. Store difficulty in server variable of session PHP
2. Check customer specific random number in server variable of session PHP
3. Check solution use timestamp less than 1 old hour

Developer check if customer solution solved?

Developer control if customer already enter valid solution to proof of work problem that uses $_SESSION['pow']['solved']

Example htdocs/pow-walled-content.php

Performance

This code execute 100-400x higher hash/sec compare pure javascript https://github.com/shenzhu2/pow-php-javascript-demo

This code execute 40% slower compare pure C. Remove I/O UI update (update_hashrate()) is more equal for C but bad UX.

Build wasm

For generate pow_wasm.js and pow_wasm.wasm use emscripten sdk

# get emscripten sdk
cd
mkdir /tmp
cd /tmp
git clone https://github.com/emscripten-core/emsdk.git
cd emsdk
git pull
./emsdk install latest
./emsdk activate latest

# get this repo code
cd /tmp
git clone https://github.com/shenzhu2/pow-php-wasm-demo.git
cd pow-php-wasm-demo/src

# compile
source /tmp//emsdk/emsdk_env.sh
emcc get_pow_solution.c sha-256.c -s EXPORTED_FUNCTIONS='["_get_pow_solution", "_malloc", "_free"]' -s EXTRA_EXPORTED_RUNTIME_METHODS='["cwrap","getValue"]' -o pow_wasm.js -O3

Troubleshoot

MIME

If it achieve MIME the error in browser can need to add "Content-Type: application/wasm" for wasm file to web server

See https://emscripten.org/docs/compiling/WebAssembly.html?highlight=mime#web-server-setup

Donate

If demo help you please make donation at monero address

4ATt62EMG6KGW6EnehvnJJABd75RavSxZY367JCb3QWzKZJzbjHexkuYQA3TwJznz1F8NgqzrgPKQ6vnxuYEpSYVMfuLEo9

Thank you!

Authors

• Shen Zhu [email protected] - 54BE 8C1D 9BC3 CD9A 554E DD69 DA4C CB93 9EB8 AAD4 - https://github.com/shenzhu2
• Alain Mosnier - https://github.com/amosnier/sha-2
• Chris Veness - https://github.com/chrisveness/crypto

License

This project is license with AGPL License. See LICENSE