Client Side Proving and Verification with Valida

While most ZK systems today are optimized for server-side execution, there is a growing need for client-side proving—where proofs are generated and verified directly on end-user devices. This shift unlocks new use cases, such as trustless light clients and private transactions, while enhancing privacy and security. 

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What is Client-Side Proving?

Client-side proving refers to the process of generating and verifying zero-knowledge proofs directly on the user's device, such as a web browser on a desktop, laptop, or mobile device. This is in contrast to server-side proving, where proofs are generated on a service provider's infrastructure.

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Client-side proving is particularly challenging due to the resource constraints of end-user devices, such as limited memory and computational power. These constraints limit the complexity of computations that can be proven and the speed at which proofs can be generated. However, client-side proving offers significant advantages, including enhanced privacy and security, as sensitive data (e.g., private keys or transaction inputs) never leaves the user's device.

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Use Cases Enabled by Client-Side Proving and Verification

Client-side proving and verification with Valida zkVM opens up a range of innovative use cases in blockchain contexts, including:

• Trustless Light Clients for Blockchains: Users can verify blockchain state transitions without relying on a centralized server, enabling decentralized and trustless interactions.
• Private Transactions: Users can prove the correctness of transactions without revealing sensitive data to third parties.
• Decentralized Identity Verification: Users can prove their identity or credentials without exposing personal information to service providers.

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How We Implemented Client-Side Proving with Valida

To support client-side proving, we compiled Valida’s execution engine, prover, and verifier to WASM using wasm-pack. This allows Valida to run directly in web browsers, enabling seamless integration into web applications.

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Key Implementation:

• Compiling to WASM: We compiled Valida’s core components to WASM, making them compatible with web browsers. This involved ensuring that the prover, verifier, and execution engine could operate within the constraints of a browser environment.
• Handling Resource Constraints: We optimized Valida to minimize memory usage and avoid panics, ensuring robust performance even in resource-constrained environments.
• Error Handling: We replaced panic conditions with proper error handling, ensuring that the prover and verifier return meaningful error messages instead of crashing. This is critical for providing a smooth user experience in client-side applications.
• Base64 Encoding for Guest Programs: To embed guest programs (the programs whose execution is being proven) into client-side applications, we base64-encoded the compiled programs and ingested them using Webpack.

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Example: Using the Valida Client-Side API

To help you get started with client-side proving, we created an example project located in the Valida toolchain at /valida-toolchain/examples/wasm/client-side-example. Here’s a high-level overview of how to use the Valida client-side API:

1. Compile the Guest Program: Use cargo +valida build --release to compile your guest program. The compiled program will be located at target/valida-unknown-baremetal-gnu/release/program.
2. Base64 Encode the Program: Encode the compiled program using a command like base64 program > program.base64.
3. Ingest the Program: Use Webpack to ingest the base64-encoded program into your client-side application. The example project demonstrates how to configure this in webpack.config.js.

Challenges and Future Work

While client-side proving is now possible with our zkVM stack, there are ongoing challenges and opportunities for improvement:

• Continuations: Enabling proofs for long-running computations by breaking them into smaller, manageable chunks.
• Usability Improvements: Enhancing the DevEx for client-side proving and verification. We welcome feedback from the community to guide these efforts.
• Optimizing for Edge Cases: Ensuring robust performance in edge cases, such as low-memory or low-power environments.

Get Started Today
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Check out the Valida client-side example and start building privacy-preserving applications in the browser! 

Read the full 0.9.0 release notes here.

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