• WASM (WebAssembly) executes smart contracts 10-100x faster than EVM (Ethereum Virtual Machine) due to its register-based architecture.
• EVM uses fixed gas metering, making transactions costly, while WASM employs dynamic metering for efficiency.
• Prone to reentrancy attacks, EVM suffers from gas-related vulnerabilities. WASM is sandboxed, enhancing security.
• WASM is multi-language development compatible (Rust, C++, etc.) and also very much suitable for future-proof applications. 
• EVM is still the dominant force in Ethereum and DeFi, but WASM is starting to pick up pace in high-performance blockchain platforms like Polkadot and Provenance.

On most blockchain platforms, smart contracts get deployed to the chain and run on a virtual machine, like Ethereum’s EVM. They execute in the blockchain’s runtime but function as independent, user-written scripts instead of being baked into the core protocol.

The core distinction between EVM and WebAssembly (WASM) lies in how deeply integrated the smart contract functionality is within the blockchain's architecture. In some blockchains, smart contract capabilities are designed as an integral part of the protocol, which can potentially enhance security and efficiency. Let's dive deeper into this issue to find out if there's any truth in this core functionality of WASM.

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What Are Virtual Machines?

Every blockchain developer knows what virtual machines are in terms of smart contracts. Nevertheless, if by any chance you have just stumbled upon this, we will briefly establish it.

A Virtual Machine (VM) is a software-built doppelgänger of a computer, enabling multiple operating systems to run on the same physical hardware like they each own the place. Abstracting the underlying hardware creates a fresh sealed virtual environment. A world within a world—it's like the movie Inception, but with operating systems.

In the context of blockchain, virtual machines execute smart contracts and decentralized applications securely and deterministically. Consequently, the code behaves predictably and cannot be altered or manipulated by external parties, such as hackers or other malicious actors. The virtual machine concept also isolates the code from off-chain data to prevent security or determinism issues.

Ethereum Virtual Machine (EVM)

EVM is where smart contracts run on Ethereum and any chain that supports it. There are tons of them out there, but some big ones include Binance Smart Chain, Avalanche, and Polygon. With an instruction set designed specifically for blockchain execution, it operates as a stack-based virtual machine, meaning that it uses a Last-In-First-Out structure for executing instructions. Each element in its stack is a 256-bit word, aligning with Ethereum's architecture.

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• Stack-based architecture: Uses a Last-In-First-Out stack to process opcodes.
• Turing complete: Capable of running any computational logic but constrained by gas costs.
• Gas metering: Every operation has a predefined gas cost to prevent resource abuse.
• Limited instruction set: Optimized for deterministic execution and security.
• Ethereum-specific opcodes: Supports instructions like SSTORE, SLOAD, CALL, and DELEGATECALL.

[.c-box-wrapper][.c-box][.c-text-center]Named after the famous World War II cryptographer Alan Turing, a Turing-complete system can perform any computation, given enough time and resources.[.c-text-center][.c-box][.c-box-wrapper]

EVM Code Example (Solidity to Bytecode)

// Simple Solidity Smart Contract
pragma solidity ^0.8.0;
contract HelloWorld {
    string public message = "Hello, World!";
    
    function updateMessage(string memory newMessage) public {
        message = newMessage;
    }
}

When compiled, the bytecode for deployment in the EVM looks something like this:

608060405234801561001057600080fd5b50604051602080610100833981018060405281019080805190602001909291905050508060008190555050609c8061004b6000396000f3fe60806040...

The Ethereum Virtual Machine runs smart contract bytecode within a sandboxed setting. 

WebAssembly (WASM)

The blockchain sector has adopted the portable binary instruction format WASM which originated for web browser use to boost performance and improve flexibility.

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Unlike EVM, WASM is a register-based virtual machine. "Register-based" here means that the virtual machine primarily uses a set of fast-access registers for computation instead of relying on a stack for storing and manipulating data. This results in greater efficiency for computation-heavy applications.

Register-based architectures are generally faster than stack-based ones since they do not require as many redundant memory operations.

• Near-native performance: Optimized for speed and compiled execution.
• Multi-language support: Compatible with Rust, C++, AssemblyScript, and more.
• Extensible instruction set: Allows future-proofing and upgrades without breaking changes.
• Better memory management: Uses linear memory instead of EVM’s account-based model.
• Built-in sandboxing: WASM runs in a secure, isolated environment, hence reducing attack vectors.

WASM Code Example (Rust to WASM)

// A simple Rust-based WASM smart contract
#[no_mangle]
pub extern "C" fn add(a: i32, b: i32) -> i32 {
    a + b
}

When compiled, this generates a WASM binary that looks like:

00000000  00 61 73 6d 01 00 00 00  01 07 01 60 02 7f 7f 01  |.asm.....`....|
00000010  7f 03 02 01 00 07 07 01  03 61 64 64 00 00 0a 09  |.......add....|

Once the WASM module is created it can then be executed on blockchain platforms that do have a WASM runtime.

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EVM vs. WASM: Performance Comparison

A big showdown between EVM and WASM is really about speed … on paper, WASM should leave EVM in the dust.

A 2024 study, "VM Matters: A Comparison of WASM VMs and EVMs in the Performance of Blockchain Smart Contracts," found that while standalone WASM engines can outperform EVM engines, eWASM implementations (WASM adapted for Ethereum) were slower than EVMs for all 256-bit benchmarks and most 64-bit benchmarks (source). The performance disparity was attributed to the overhead introduced by gas metering and inefficient context switching in the Ethereum environment.

Despite the study's findings, you have to keep in mind that standalone WASM engines still have significant advantages in different scenarios. This covers everything from non-Ethereum blockchains and advanced smart contracts to handling multiple transactions at once—unlike Ethereum, which processes them one by one like a slow-moving checkout line.

All this is to say that it is not that easy to conclusively determine whether WASM or EVM is faster in terms of transaction processing on Ethereum. However, if you want to compare blockchains to each other without focusing on EVM vs. eWASM, you could say that WASM infrastructure is a considerable asset for chains wielding it.

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Memory Management

• EVM Storage Model: Data is stored persistently in the so-called account-based storage model — where each account maintains its own storage, typically structured as key-value pairs — it can make storage operations expensive.‍
• WASM Storage Model: Operating with linear memory, meaning a contiguous block of addressable memory that grows dynamically, it allows for more efficient handling of data, reducing overhead.

With the above-mentioned caveat, WASM-based smart contracts can execute approximately 10-100 times faster than their EVM counterparts. This is due mainly to WASM’s register-based architecture, which avoids unnecessary memory operations, making execution significantly more efficient. In contrast, EVM’s stack-based model means that each computation must go through a more complex series of push-and-pop operations.

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Security Considerations

EVM security is strongly sandboxed, providing a controlled execution environment, but it remains prone to reentrancy attacks and opcode limitations, meaning low-level machine instruction on basic tasks. If not carefully managed, this can be exploited. WASM security is more extensible and allows more freedom in smart contract development, but it requires proper sandboxing and memory management to safeguard its safety.

Gas Fees

When evaluating smart contract platforms, gas fees obviously play a huge role. 

EVM gas pricing is deterministic, where each operation has a predefined gas cost. For example:

• SLOAD (storage read) costs 2,100 gas
• SSTORE (storage write) costs 20,000 gas
• CALL (external contract call) costs 700 gas

However, these gas costs can accumulate quickly, making complex contracts expensive to execute. WASM-based blockchains, like Polkadot and Near, introduce dynamic gas metering, where execution cost is based on computational complexity rather than a fixed price per operation. As a direct result, WASM environments are more adaptable and cost-efficient in real-world applications.

Adoption and Use Cases to Conclude

Where EVM is Preferred:

• Ethereum-compatible blockchains (Ethereum, BSC, Avalanche C-Chain, Polygon).
• DeFi protocols that rely on Solidity and EVM tooling.
• Legacy contracts must be compatible with the Ethereum infrastructure to function.

Where WASM Comes Handy:

• High-performance applications requiring near-native execution speed.
• Multi-language smart contract development (e.g., Rust, C++).
• Blockchains like Polkadot, Near, and Provenance, where WASM is the native execution environment.

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