cequencer / design

eWASM Design Overview and Specification

Ethereum flavored WebAssembly (eWASM) Design

This repository contains documents describing the design and high-level overview of eWASM. Expect the contents of this repository to be in flux: everything is still under discussion.

What is WebAssembly?

WebAssembly (or WASM for short) is a new, portable, size- and load-time-efficient format. WebAssembly is currently being designed as an open standard by a W3C Community Group.

Please review the WebAssembly design and instruction set first.

A few key points:

• WebAssembly defines an instruction set, intermediate source format (WAST) and a binary encoded format (WASM).
• WebAssembly has a few higher level features, such as the ability to import and execute outside methods defined via an interface.
• LLVM includes a WebAssembly backend to generate WASM output.
• Major browser JavaScript engines will notably have native support for WebAssembly, including but not limited to: Google's V8 engine (Node.js and Chromium-based browsers), Microsoft's Chakra engine (Microsoft Edge), Mozilla's Spidermonkey engine (Firefox and Thunderbird).
• Other non-browser implementations exist too: wasm-jit-prototype (a standalone VM using an LLVM backend), wabt (a stack-based interpreter), ml-proto (the OCaml reference interpreter), etc.

What is Ethereum flavored WebAssembly (eWASM)?

eWASM is a restricted subset of WASM to be used for contracts in Ethereum.

eWASM:

• specifies the VM semantics
• specifies the semantics for an eWASM contract
• specifies an Ethereum environment interface to facilitate interaction with the Ethereum environment from an eWASM contract
• specifies system contracts
• specifies metering for instructions
• and aims to restrict non-deterministic behavior
• specifies a backwards compatible upgrade path to EVM1

Goals of the eWASM project

• To provide a specification of eWASM contract semantics and the Ethereum interface
• To provide an EVM transpiler, preferably as an eWASM contract
• To provide a metering injector, preferably as an eWASM contract
• To provide a VM implementation for executing eWASM contracts
• To implement an eWASM backend in the Solidity compiler
• To provide a library and instructions for writing contracts in Rust
• To provide a library and instructions for writing contracts in C

Glossary

• eWASM contract: a contract adhering to the eWASM specification
• Ethereum environment interface (EEI): a set of methods available to eWASM contracts
• metering: the act of measuring execution cost in a deterministic way
• metering injector: a transformation tool inserting metering code to an eWASM contract
• EVM transpiler: an EVM bytecode (the current Ethereum VM) to eWASM transcompiler

Resources

• FAQ
• Rationale
• VM semantics
• Ethereum environment interface
• eWASM Contract Interface
• System contracts
• Backwards compatibility instructions
• Original Proposal (EIP#48)
• WabAssembly Specification
• WebAssembly design documents

Projects

• ewasm-tests
• wasm-metering
• ewasm-kernel
• evm2wasm
• c-libeth
• rust-libeth

Design Process & Contributing

For now, high-level design discussions should continue to be held in the design repository, via issues and pull requests. Feel free to file issues.

Chat

Matrix
IRC freenode@ewasm
Gitter