This is the below code

 cast sig "workMyDirefulOwner(uint256,uint256)"                                      
 cast sig "transfer(address,uint256)"                 

2 Answers 2


The function signature is just the beginning of a hash of the function name and its parameters - as you can see.

If you perform the hashing manually, the actual hash is a lot longer. The hashes would then not be the same. But Ethereum uses only the first 8 characters of the full hash. That means that (hash) collisions are a lot more probable. This is also why your two function signatures result in the same signature hash.


Function signatures are deterministically calculated in the context of Solidity contracts. They are nothing but a keccak256 hash of the function name along with the parameter types.

For ex, if you function is transfer(address _recipient, uint256 amount), the signature would be keccak256 of transfer(address,uint256) which would result in the following hash:


Whereas, during run time the EVM uses function selectors to invoke a function call to a specific method. Function selectors are first 4 bytes (0xa9059cbb from the above example) of the function signature. So the can be function selectors can collide, but function signatures can never be the same for 2 functions.

Some useful resources:

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