Does NONCE have to be continuous?

[itsmesoh]

Hi,

Maybe a simple question but i would really appreciate if someone can help here.

Does the Nonce value have to be continuos? As in the first one from a wallet will have nonce value as 0, the next transaction will have 1 and then 2..3...4..5.. etc.

Is it possible to have a transaction in a wallet with a random value for nonce?

thank you in advance.

[ricmoo]

Yes. A transaction won’t be mined until the previous nonce has been mined. It can be used as a way to ensure the order of multiple transactions.

But requiring the values be sequential, it means for any given account, all we need to store is the number of transactions sent. If it was “any” random number we would need to keep a list of every nonce ever used and check it for every transaction. This way we can just keep one value around, look it up and use it.

When I first began in Ethereum, I had the exact same question and assumption based on how I’d used the term nonce up until that point. In fact my first wallet just used a random number and I was confused why things didn’t work. :)

As an aside, a common technique for Smart Wallets is to use a 2D nonce, which will afford some very cool schemes for publishing transactions. But I’ll go into that with the EIP-4337 release. :)

[itsmesoh]

Thank you for the response, @ricmoo.

So we should check the latest nonce count and then increment and provide for the next transaction.
In this scenario, if we make 2 transactions back to back and the first one (Nonce=678) fails for some reason, the second one (Nonce=679) will be stuck in the queue. And now if we create a new transaction to recreate the first transaction, it will have the incremented value for nonce (Nonce=680). This in turn will again be stuck in the queue since the blockchain is waiting or transaction with Nonce 678.

This is a tricky situation and do you have any suggestions or best practices on how to tackle this situation???

Thank you again for the valuable inputs you give. :)

[ricmoo]

You have to be careful by what you mean by fail. If the transaction reverts, but is mined, then the nonce is used and the next will still be valid. If you submit a nonce of 5 and 6, and you replace it with a new 5 and 6 before it is mined, keep in mind you still signed all 4 transactions and they exist out in the world. It is possible after 5b gets mined for 6a to be mined instead of 6b.

When strict ordering is mission critical, usually the best solution is to use a smart contract wallet, and use it to execute the necessary transactions atomically. A smart contract wallet with multicall functionality is by far the safest way to interact with the blockchain when multiple operations are required. With the use of 2D nonces, you can also ensure you invalidate all existing transactions that may exist in the mempool before submitting the set of replacement transactions.

Once you sign anything and release it to the mempool, anyone could store a copy of that. A classic example was ERC-20 tokens, which have an approval. Imagine if I approve 10 tokens with tx1=approve(10), but then decide I'd rather approve 20 tokens instead, so I create a tx2=approve(20). An attacker that has access to a miner could do the following, mine tx1, take 10 tokens (the current approval is now for 0) and then execute tx2 and take 20 tokens. So, they were actually able to take a total of 30 tokens. In this case the only safe thing would be to do tx2=approve(0), wait for it to be mined, and then do tx3=approve(20).

Paying attention to what is out in the wild is important. Which is why I'm also bullish on Smart Contract Wallets. They enable a lot of safety not otherwise possible with normal EOAs. :)