generate function name yielding a specific function selector

Question

Suppose I have a function with arguments (address _to, uint256 number) The function selector is found using

let signature = "name(address,uint256)";
let selector = Keccack256(signature) ;

I want to find a name for my function that will generate a specific selector say for example, 0x19284901. How would I do this ?

Franfran · Accepted Answer · 2022-06-21 19:54:48Z

1

You cannot retro engineer the byte selectors, those are made from the keccack256 hashing as you shown it.

Though, you can use 4 bytes selectors database that are free to use, here is the example of one: https://www.4byte.directory/docs/

If you cannot find the selector that you need, you can brute force (creating a random function name, until getting the correct function selector)

answered Jun 21, 2022 at 19:54

Franfran

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How would you do that
– qubitz
Commented Jun 21, 2022 at 19:56
The function selector that you need is not in the db ?
– Franfran
Commented Jun 21, 2022 at 20:18
No I really need to generate an arbitrary function selector from the arguements
– qubitz
Commented Jun 21, 2022 at 20:29
So you can run a loop until you find the correct 4 bytes selector. For this, just alter the function name until that the condition is met, e.g. ``` let selector while selector !== "0x19284901" { const random_name = some_random_name(); const full_name = random_name + "(address,uint256)"; const selector = keccak256(full_name); } print(selector); ``` Please note that it's pseudo-code, for you to understand easily.
– Franfran
Commented Jun 22, 2022 at 17:02

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