# What happens if by randomness you deploy a contract to the same address then an existing EOA

What happens if by randomness you deploy a contract to the same address then an existing EOA?

Would the deployment be rejected? Would it only be rejected if the EOA has no transaction history i.e a nonce of 0?

You should check EIP-3607

``````Ethereum addresses are currently only 160 bits long.
This means it is possible to create a collision between a contract account
and an Externally Owned Account (EOA) using an estimated 2**80 computing operations,
which is feasible now given a large budget (ca. 10 billion USD).
The fix in this EIP prevents the worst possible attack, where a safe looking contract
(e.g. a token wrapper or an AMM-type contract) is deployed to attract user funds,
which can then be spent using the EOA key for the same address.
``````

tldr is that it's possible for an attacker to do, even if it would cost a lot of money, but the EIP-3607 is already implemented and theoretically mitigates that possibility

• Thanks for the reply. I presume 2**80 gives you a 50% chance to deploy your contract to the same address? How do they get to a value of 10 billion USD that it would cost to do so? Commented Oct 27, 2022 at 8:03
• Any idea @OlivierD? Commented Dec 4, 2022 at 20:13
• Well since we are talking about power of and exponents here, 50% change would be 2^159. So here, 2^80 is 12089 2581961462 9174706176. So each compute, you have 1 chance out of 12089 2581961462 9174706176 to have a collision. But with a powerful computer making, let's say, 10 billions compute a seconde, you could eventually get a collision (even if it would take time and cost 10 billions USD). Not a PhD in math so don't quote me here Commented Dec 6, 2022 at 9:49