Unencrypted Private Data On Chain

1. Search for state variables storing passwords, secrets, keys, answers, or seeds — regardless of visibility modifier
2. Check if any private variable is relied upon for confidentiality (not just access control)
3. Look for game/lottery logic where hidden information is stored on-chain before a reveal phase
4. Check constructor parameters and transaction calldata for sensitive values — these are publicly visible on block explorers
5. Search for comments like "secret", "hidden", "private key", "password" near storage declarations

False Positives

• Data is encrypted or hashed before storage (e.g., commitment hash in a commit-reveal scheme)
• The private modifier is used correctly for access control between contracts, not for data confidentiality
• The "sensitive" data is actually public information (e.g., a contract address)

Remediation

• Never store plaintext secrets on-chain — all storage is publicly readable
• Use commit-reveal schemes for hidden inputs: store keccak256(secret || salt) first, reveal later
• For truly private data, keep it off-chain and only store hashes/commitments on-chain
• Consider zero-knowledge proofs for verifiable computation on private data

// Commit-reveal scheme
mapping(address => bytes32) public commitments;

function commit(bytes32 hash) external {
    // User submits keccak256(answer, salt) — answer stays private
    commitments[msg.sender] = hash;
}

function reveal(bytes32 answer, bytes32 salt) external {
    require(commitments[msg.sender] == keccak256(abi.encodePacked(answer, salt)));
    _processAnswer(msg.sender, answer);
}