Why store account nonce on chain instead of using timestamp to prevent replay attacks?

Question

Why store account nonce on chain instead of using timestamp to prevent replay attacks, or any other random bit of information that will change thr hash and differentiate the transaction?

As far as I was able to understand, the account nonce is a bit of information added to a transaction to counteract replay attacks by making the transaction hash used to identify the account unique.

My question is, why is there a need for a permanent record that occupies space on the chain of the amount of transaction each account has made? Couldn't the same effect be achieved with the addition of any other kind of random or unique data to the transaction, such as a timestamp at the moment the transaction is generated by the wallet client? Is there any other advantage to recording account nonces that I am failing to see?

Answer 1

First of all, transactions don't have a timestamp. Only the blocks have timestamps.

Now you may ask why didn't we simply use timestamps instead of nonce; technically speaking, it would have worked equally fine. I guess it had more to do with design choice. Consider the billions of transactions and then each transaction holding multiple bytes for the timestamp, a nonce is comparatively smaller in size. And actually if you look at it programmatically, a nonce is more sort of a notion of ordering (much like a timestamp.) Additionally, you get transaction count as well.

Effectively, you're getting three benefits when using nonce- less space, simplicity, ordering, and tracking number of transactions. The most important being the fact by the virtue of the decentralized nature of the Ethereum network, you need to make sure that a transaction A was not lost, and hence the EVM won't process transaction B, assuming transaction A was supposed to happen before B. You can think of it as transactions will be executed in order despite the network latency each transaction experiences (very much like TCP packets, if the analogy helps.) This can't be achieved with mere timestamps.

Additionally, you should be aware that timestamps in the network can be artificially modified by the miner nodes.