FAQ

Frequently asked questions about ZKPDF, covering common issues, troubleshooting, and best practices.

ZKPDF is a zero-knowledge proof system for verifying PDF documents. It allows you to cryptographically prove properties about PDFs (like specific text appearing at exact positions or valid digital signatures) without revealing the entire document content.

What are the main use cases for ZKPDF?

Document Authentication: Prove a document is signed by a trusted authority
Selective Disclosure: Reveal specific fields from government-issued certificates
Smart Contract Integration: Use verified document facts in blockchain applications
Fraud Prevention: Detect if documents have been tampered with
Compliance: Meet regulatory requirements for document verification

Is ZKPDF production-ready?

ZKPDF is actively developed and used in production environments. However, it's important to:

Test thoroughly with your specific PDF types
Understand the limitations (see Architecture)
Implement proper error handling
Consider performance implications for large documents

Technical Questions

What PDF formats are supported?

ZKPDF supports standard PDF files with the following features:

✅ Text extraction from PDF streams
✅ Digital signatures (RSA-SHA256, SHA384, SHA512)
✅ Multi-page documents
✅ Compressed streams
❌ Images (extraction not supported)
❌ Form fields
❌ ECDSA signatures
❌ Complex layouts

How accurate is text extraction?

Text extraction accuracy depends on:

Font encoding: Better accuracy with standard encodings
PDF structure: Well-structured PDFs extract more accurately
Font types: Some custom fonts may not extract perfectly
Layout complexity: Simple layouts extract better than complex ones

What signature algorithms are supported?

Currently supported:

✅ RSA-SHA256
✅ RSA-SHA384
✅ RSA-SHA512
❌ ECDSA signatures
❌ DSA signatures

How do I check if my PDF is compatible with ZKPDF?

Use the ZKPDF Compatibility Checker to verify if your PDF will work with zkPDF:

🔗 https://privacy-ethereum.github.io/zkpdf/

Simply drop your PDF file into the compatibility checker to:

✅ Verify digital signature compatibility
✅ Check PDF structure and format
✅ Test text extraction capabilities
✅ Validate signature algorithms

This tool helps you determine if your PDF will work with zkPDF before implementing it in your application.

How do I handle different PDF generators?

Different PDF generators may produce different byte layouts. To handle this:

Use offset ranges instead of exact offsets
Test with multiple PDF generators
Use signature verification for authenticity
Implement fallback strategies

#![allow(unused)]
fn main() {
// Instead of exact offset
let result = verify_text(pdf_bytes, 0, "CONFIDENTIAL", 100)?;

// Use offset range
let result = verify_text_range(pdf_bytes, 0, "CONFIDENTIAL", 90, 110)?;
}

Can I run ZKPDF on client-side mobile or browser?

No, you cannot run ZKPDF on client-side mobile or browser. ZKPDF is computationally heavy and requires significant resources that are not available in mobile browsers or client-side environments. The zero-knowledge proof generation process involves:

Heavy cryptographic computations requiring substantial CPU power
Large memory requirements (hundreds of MB to GB)
Complex PDF parsing and signature verification
Proof generation that takes 30-60 seconds even on powerful servers

Recommended approach: Use server-side proving with the Succinct Prover Network or your own server infrastructure, then verify proofs on-chain or through API calls.

Integration Questions

How do I integrate ZKPDF with my application?

Integration depends on your use case:

Rust applications: Use the library directly
Web applications: Use WASM bindings
Node.js applications: Use the prover API
Smart contracts: Deploy verification contracts

Can I use ZKPDF with other blockchain networks?

Yes, ZKPDF proofs can be verified on any network that supports the SP1 verifier:

✅ Ethereum
✅ Polygon
✅ Arbitrum
✅ Optimism
✅ Other EVM-compatible networks

How do I deploy verification contracts?

Deploy SP1 verifier (if not already deployed)
Get program verification key
Deploy PdfVerifier contract
Test with sample proofs

# Deploy contract
forge create --rpc-url $RPC_URL \
  --private-key $PRIVATE_KEY \
  src/PdfVerifier.sol:PdfVerifier \
  --constructor-args $SP1_VERIFIER_ADDRESS $PROGRAM_VKEY

What if I need to support new PDF features?

ZKPDF is designed to be extensible:

Fork the repository
Add new features to pdf-utils
Update circuits if needed
Submit pull request

This project uses ZKPDF for PDF verification.
https://github.com/privacy-ethereum/zkpdf

Next Steps

Examples: Practical usage examples
API Reference: Complete API documentation
Proving: Generate proofs from your circuits
Verification: Verify proofs on-chain

ZKPDF Documentation

FAQ

General Questions

What is ZKPDF?