truebitfoundation/ocaml-offchain

Fork of WebAssembly reference interpreter with support for generating proofs needed for blockchain verification

Installation of the off-chain interpreter

These instructions were tested on Ubuntu 17.04.

First install dependencies

apt-get install -y wget gcc ocaml opam libzarith-ocaml-dev m4 pkg-config zlib1g-dev
opam init -y
eval $(opam config env)
opam install cryptokit yojson

Then go to the interpreter directory of the repo

cd interpreter
make

If the build fails it may be due to an outdated version of ocaml. To upgrade simply run opam switch 4.06.0, and then follow the steps above starting with eval $(opam config env).

This should generate the executable wasm in the interpreter directory.

Testing the off-chain interpreter

./wasm -m ../test/core/fac.wast

If there are no errors, it means that the tests were passed.

./wasm -t -m ../test/core/fac.wast

This command will print the trace messages, it will basically output every instruction that the interpreter runs.

Outputting proofs:

./wasm -case 0 -step 4 -m ../test/core/fac.wast

This will make a proof for step 4 in the computation. Because there are many test cases, one of them has to be selected, so for example -case 0 will select the first test case.

Using the JSON-RPC Server

cd server
npm install
node index.js

A client can communicate with the server like this:

var jayson = require('jayson');

// create a client
var client = jayson.client.http({
  port: 3000
});

// invoke *command* with *args*
client.request('*command*', [*args*], function(err, response) {
  if(err) throw err;
  console.log(response.result);
});

Docker

If you want to run these tests inside of a Docker container you can pull the latest docker image and try it out.

docker run --name tb-offchain -ti hswick/ocaml-offchain:latest`
cd webasm/interpreter
./wasm -t -m ../test/core/fac.wast