Wasm for Smart Contracts

WebAssembly (Wasm) for Smart Contracts offers a transformative approach to Web3 development by providing near-native execution efficiency, enhancing the speed and modularity of smart contracts across various blockchain platforms, while highlighting the benefits, limitations, and security considerations of using Wasm in contrast to traditional EVM-based smart contracts.

May 31, 2024

WebAssembly (Wasm) for Smart Contracts: Transforming Web3


Web3 Security researchers, Audit Firms, and smart contract developers are constantly seeking more efficient, secure, and scalable solutions for blockchain applications. The primary approach to creating smart contracts involves using languages designed for the Ethereum Virtual Machine (EVM), such as Solidity and Vyper. However, these languages, while effective, face limitations in execution speed when compiled to 256-bit runtimes, leading to slower performance. Enter WebAssembly (Wasm) – a binary instruction format that promises near-native execution efficiency, providing a transformative approach to Web3 development.

In-Depth Background

WebAssembly (Wasm) is a binary instruction format for a stack-based virtual machine, designed to be a portable, performance-oriented solution compatible with most web browsers. It has four number types of 32- and 64-bit integers and floats (i32, f32, i64, and f64) and uses linear memory. Wasm's minimalistic design and superior execution efficiency have led to its widespread adoption by prominent blockchain platforms such as Radix, Near, and EOSIO, where it serves as the runtime for smart contracts.

The growing list of blockchain protocols supporting compilation to Wasm includes:

  • Radix
  • Near
  • Astar & Shiden
  • Elrond
  • Cosmos SDK
  • Polkadot SDK
  • Internet Computer
  • Kusama
  • Secret
  • Casper
  • Vexanium
  • Parity's Kovan testnet for Ethereum

Understanding Wasm Smart Contracts

Wasm smart contracts are typically written in languages like Rust and Go, with other popular languages including nk!, C/C#/C++, AssemblyScript, TypeScript, Motoko, and more. These contracts involve standard contract storage, permission, and account management logic. Unlike traditional execution environments, Wasm contracts are modular, easily modified to meet specific blockchain requirements. This modularity and cross-platform compatibility make Wasm an advantageous choice for developing efficient decentralized applications (dApps).

The Case for Wasm in Smart Contracts

Efficient and Fast

Wasm executes at near-native speeds due to its 32-bit word size, which aligns with modern hardware semantics, making it significantly more efficient than 256-bit architectures used by platforms like Ethereum’s EVM. This efficiency extends to various blockchain operations, with potential speed improvements in the thousands.

Broader Technical Characteristics

  • Size: Wasm contracts are generally comparable in size to EVM contracts, making them suitable for space-constrained blockchain environments.
  • Security: Wasm offers a memory-safe, sandboxed execution environment, enforcing web environment’s same-origin and permissions security policies.
  • Language Support: Wasm supports compilation from various high-level languages, providing flexibility and inclusivity, though limited by the blockchain platform’s SDK and API requirements.
  • Cross-Platform Portability: Wasm’s binary format allows for efficient execution on both web and non-web embeddings, enabling code to run on different platforms with minimal alterations.

Wasm Limitations


Wasm’s debugging tools for blockchain applications are still evolving, making EVM debugging easier due to established tools. However, Wasm offers a human-readable text format (.wat) for debugging and testing, though it is rarely used in practice.

Memory Safety

Wasm lacks integrated memory safety mechanisms like stack canaries and address space layout randomization (ASLR), which, while not critical for blockchain, can pose challenges.

Wasm Smart Contract Vulnerabilities

Wasm smart contracts, like their Ethereum counterparts, have inherent vulnerabilities. Researchers have identified vulnerabilities in Wasm contracts, particularly those compiled from memory-unsafe languages like C and C++. These vulnerabilities necessitate enhanced security measures through thorough code reviews during development and execution.

Language Support & Development Tools

Wasm supports various languages, including Rust, C/C++, AssemblyScript, C#, Dart, and more, though the development tools for Wasm are still maturing compared to EVM. Some notable tools include:

  • LLVM: Provides a modular and reusable compiler and toolchain technologies.
  • Wasmcov: A Rust library for automated coverage analysis of Wasm executables.
  • WASMOD: A research prototype for detecting overflow vulnerabilities in Wasm.

Developing Smart Contracts in Wasm Using Ink!

Ink! is a Rust language extension that uses the Contracts pallet for writing Wasm smart contracts. It supports multiple constructor functions, variable storage entries, and offers tools like Swanky Suite and OpenBrush for streamlined development.

Wasm’s Future Outlook

Wasm represents a paradigm shift in smart contract development. Instead of creating specialized languages for each platform, Wasm offers a general-purpose virtual machine and bytecode for secure and scalable execution. Its modular nature allows for adaptable smart contracts across different blockchains, providing a new architectural model for cross-platform applications.

Case Studies


Polkadot has integrated Wasm as its primary runtime, leveraging its efficiency and cross-platform compatibility for enhanced blockchain operations. Polkadot’s modularity allows developers to build cross-compatible dApps with ease, showcasing Wasm’s transformative potential.


EOSIO utilizes Wasm for its smart contract execution, benefiting from its performance efficiency and secure environment. This adoption has enabled EOSIO to offer robust and scalable dApps, reinforcing Wasm’s significance in the blockchain ecosystem.

Expert Conclusion

Wasm’s integration into blockchain development is set to revolutionize the field, providing a secure, efficient, and scalable environment for smart contracts. As more projects incorporate Wasm, its potential to transform Web3 becomes increasingly evident.

What TRUSTBYTES Recommends:

  • Engage in community discussions to share insights and developments in Wasm technology.
  • Access further training resources to stay updated on the latest advancements in Wasm and smart contract development.
  • Explore advanced security tools to enhance the robustness of your Wasm smart contracts.

For further insights on the Web3 security space and engagement with top-tier smart contract auditors in the industry, join our TRUSTBYTES Discord.


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