The problem ProofOS solves

Right now, if you hold ₹2Cr in ETH, you cannot:

• Get a home loan (banks won't accept wallet statements as income proof)
• Apply for a US visa (embassies want bank statements, not transaction exports)
• Pass an audit (CAs need verifiable tax records, not spreadsheets)
• Prove solvency to a business partner (without handing over your entire wallet history)

The current options are bad:

• Export your full wallet history → privacy gone
• Trust a CA with raw data → no cryptographic guarantee
• Use existing tools (KoinX, Cleartax) → they give you a PDF, not a proof

ProofOS lets you prove facts about your money without revealing your money.

Generate a ZK proof that says:

• "I earned ₹40L this year" (for a bank loan)
• "I paid ₹6.2L in taxes" (for an auditor)
• "My net worth is above ₹50L" (for a visa application)

...all backed by on-chain verification. No transaction history exposed. No trust required.

Who it's for:

• Crypto freelancers applying for visas
• Traders getting home loans
• Family offices managing 20+ wallets (via ENS)
• Anyone filing ITR-VDA who wants a verifiable proof

The tax calculator is the entry point. The real product is financial credibility for crypto-native India.

Challenges we ran into

1. Cairo u256 ≠ Solidity u256

Starknet uses u256 { low: u128, high: u128 }. Ethereum just has uint256. When we bridged the tax value from Cairo to Solidity via L2→L1 messaging, the Ethereum contract read garbage values because we didn't pack/unpack correctly.

Fix: Split the u256 into two uint128 values in the Cairo message payload, then reconstructed it in Solidity as (high * 2^128) + low. Took 3 failed message consumptions to debug.

2. Starknet L2→L1 messages don't appear instantly

The proof gets committed on Starknet, then bridged to Ethereum via send_message_to_l1_syscall. But the message doesn't show up in Starknet Core immediately - you have to wait for finalization.

Fix: Added a polling loop in the frontend that checks isVerified() every 10 seconds. Shows the user a spinner with "waiting for Starknet finalization" instead of letting them spam the verify button.