ABI Encoder and Hashing Demo in DeFi

This project demonstrates advanced data encoding techniques essential for DeFi protocol development using Solidity's abi.encode, abi.encodePacked and keccak256 functions. It provides a complete set of encoding and hashing functions to create unique identifiers across DeFi operations such as liquidity pools, trading positions, limit orders, yield farming strategies or cross-chain operations. All logic is covered by a complete testing suite with 100% test coverage.

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🔑 Encoding in Solidity: abi.encode vs abi.encodePacked

ABI (Application Binary Interface) encoding is the standard method for encoding function calls and data in Ethereum.

Feature	abi.encode	abi.encodePacked
Encoding Type	Full padding (32-byte slots)	Compact, no padding
Gas Cost	Higher due to padding overhead	Lower due to compression
Security	No collision risk	Potential collision risk with dynamic types
Output Size	Larger, predictable structure	Smaller, minimal footprint
Example	uint16(0x1234), uint16(0x5678) → 64 bytes	uint16(0x1234), uint16(0x5678) → 4 bytes (0x12345678)

🔐 keccak256(encodedData) is a cryptographic hashing function widely used in the Ethereum ecosystem to generate unique identifiers from encoded data. The encoded data is passed through the hashing function, which produces a unique bytes32 value. Key cryptographic hash properties:

• Fixed-size output: Regardless of the input size, it always returns a 32-byte value.
• Deterministic: The same input will always produce the same output.
• Collision resistance: It is computationally infeasible to find two different inputs that result in the same hash.
• Preimage resistance: It is practically impossible to reverse the process and deduce the original input from the hash (one-way function).
• Avalanche effect: A change of even a single bit in the input results in a completely different hash output.

DeFi Use Cases

In DeFi protocols, hashing and encoding is crucial for:

• Unique Identifiers: Pool IDs, position tracking, order management
• Hash Generation: Creating deterministic, collision-resistant identifiers
• Gas Optimization: Minimizing transaction costs through compact encoding
• Cross-Protocol Compatibility: Standardized data formats across DeFi ecosystem

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⚙️ Functions Implemented

Each function encodes specific DeFi concepts into bytes and/or hashes them with keccak256 for uniqueness and integrity.

• createPoolIdentifier – Generates unique pool IDs based on token pair and fee, invariant to token order.
• encodeTradingPosition – Encodes user trading positions with timestamp and produces a unique position hash.
• encodeSwapData – Encodes swap paths, amounts, and deadline while validating input consistency.
• encodeLimitOrder – Encodes data of a limit order with a string identifier.
• encodeYieldPosition – Hashes data from a yield farming position.
• encodeFlashLoanData – Concatenates flash loan parameters plus callback data.
• encodeStakingPoolConfig – Encodes staking configuration including block timestamp for uniqueness.
• createUserMultiPoolHash – Builds a unique user identifier across multiple pools.
• encodeYieldStrategy – Encodes yield strategies data, pool allocation and weights.
• encodeCrossChainBridgeData – Encodes cross-chain transfer data.
• createDeFiTransactionId – Produces unique IDs for DeFi transactions.
• encodeStopLossOrder, encodeTakeProfitOrder, encodeTrailingStopOrder – Encodes risk management orders with discriminators.

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🧪 Testing

The project implements exhaustive testing patterns essential for production DeFi protocols. Test includes functions like:

✅ Invariant testing: to verify token ordering consistency regardless of input order. test_createPoolIdentifier_sameForBothTokenOrders()

✅ Happy path: to ensure the correct verification of encoded data and hash generation test_encodeTradingPosition_returnsExpectedDataAndHash()

✅ Negative cases: to prevent from malformed input data and revert cases validation. test_encodeSwapData_revertsOnLengthMismatch()

💯 100% Code Coverage is achieved across all metrics:

Ran 17 tests for test/ABIEncoderDemo.t.sol:ABIEncoderDemoTest
Suite result: ok. 17 passed; 0 failed; 0 skipped

╭------------------------+-----------------+-----------------+---------------+-----------------╮
| File                   | % Lines         | % Statements    | % Branches    | % Funcs         |
+==============================================================================================+
| src/ABIEncoderDemo.sol | 100.00% (52/52) | 100.00% (51/51) | 100.00% (4/4) | 100.00% (14/14) |
╰------------------------+-----------------+-----------------+---------------+-----------------╯

⚒️ Technologies Used

• Solidity (^0.8.24) – Smart contract programming language
• Foundry – Advanced testing framework with fuzzing and invariant testing

📜 License

This project is licensed under the MIT License.