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Proof verification can only be performed together with Proof Generation.

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How to use?

Follow instructions for Proof Generation, but select PROOF_VERIFICATION_ON_L1 as result. After a proof is verified, you can call isCairoFactValid(bytes32 fact_hash, bool is_mocked) on the Satellite contract. You can also set mockFactHash to omit actual proof verification on-chain, reducing the cost for testing purposes.

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Calculating fact hash

On EVM chains, fact hash is calculated from programHash and output array in the following way: 
// Output has to match the output of the program and can have any length
uint256[] memory outputs = new uint256[](2);
outputs[0] = 10;
outputs[1] = 55;

bytes32 outputHash = keccak256(abi.encodePacked(outputs));

// Program hash is constant for given program, regardless of input and output, so it can be hardcoded
bytes32 programHash = bytes32(uint256(0x407908712e70dd914b006062d8d70bd8aeae06bcfc973cbd4309e7f3a2e825b));

bytes32 fact = keccak256(abi.encode(ms.programHash, outputHash));