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docs/contract.md

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+# Obsero Smart Contract Specification
+
+The smart contract anchors proof hashes on the Base blockchain.
+
+## Functions
+
+```solidity
+function submitProof(bytes32 hash, string calldata cid, uint256 timestamp) external;
+```
+
+## Events
+
+```solidity
+event ProofSubmitted(address indexed observer, bytes32 hash, string cid, uint256 timestamp);
+```
+
+## Requirements
+
+- The hash must match the signed JSON proof.
+- CID must point to a valid IPFS document.
+- Timestamps must be reasonable compared to block timestamp.