Solidity – Which Was Standard in Solidity Compiler Before Solidity 0.5: abi.encodePacked or abi.encode?

byteskeccaksolidity

Before Solidity v0.5, keccak256() took multiple arguments, and after v0.5 it requires a single bytes argument. Which of the two encoding types, encode/encodePacked, did the compiler use?

Best Answer

It was abi.encodePacked(). keccak256(abi.encodePacked(a, b, c)) on 0.5+ is equivalent to keccak256(a, b, c) in earlier versions.

Solidity v0.5.0 Breaking Changes > Semantic and Syntactic Changes

The functions .call(), .delegatecall(), staticcall(), keccak256(), sha256() and ripemd160() now accept only a single bytes argument. Moreover, the argument is not padded. This was changed to make more explicit and clear how the arguments are concatenated. Change every .call() (and family) to a .call("") and every .call(signature, a, b, c) to use .call(abi.encodeWithSignature(signature, a, b, c)) (the last one only works for value types). Change every keccak256(a, b, c) to keccak256(abi.encodePacked(a, b, c)).

Related Solutions

[Ethereum] Web3js and keccak different values

Try this:

web3.sha3(web3.padRight(web3.fromAscii("test1"), 66), { encoding: 'hex' });

Explanation:

A bytes32 representation of "test1" is 32 bytes long, while "test1" is only 5 bytes long.

web3.fromAscii("test1") converts the string to its hexadecimal representation with a leading "0x": 0x7465737431.

web3.padRight pads the value with zeros on the right-hand side, like the conversion to bytes32 does. 32 bytes is 64 hexadecimal characters, but to take into account the leading "0x", I'm padding to 66 characters. This producets 0x7465737431000000000000000000000000000000000000000000000000000000, which is a bytes32 representation of the string.

Finally, we pass this value to web3.sha3 and specify the { encoding: 'hex' } option so sha3 interprets the value passed in as hexadecimal rather than ASCII.

[Ethereum] SOLIDITY: How to get a bytes32 keccak256 hash of an address and 2 uint256 variables

As reported in this thread: https://github.com/ethereum/solidity/issues/3955

The new abi.encode*() methods offer a replacement to perform packing, which then can be passed to all these hashing functions.

Bottom line: As @mirg commented, just use abi.encodePacked() inside keccak256(). That is:

keccak256(abi.encodePacked(msg.sender, _unixTimestamp, _timeExpired))

Best Answer

Related Solutions

[Ethereum] Web3js and keccak different values

[Ethereum] SOLIDITY: How to get a bytes32 keccak256 hash of an address and 2 uint256 variables

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